Date
stringlengths 11
18
| Link
stringlengths 62
62
| Title
stringlengths 16
148
| Summary
stringlengths 1
2.68k
| Body
stringlengths 22
13k
⌀ | Category
stringclasses 20
values | Year
int64 2k
2.02k
|
|---|---|---|---|---|---|---|
August 10, 2020
|
https://www.sciencedaily.com/releases/2020/08/200810141002.htm
|
New study confirms the power of Deinosuchus and its 'teeth the size of bananas'
|
A new study, revisiting fossil specimens from the enormous crocodylian,
|
And, it wasn't alone!The research, published in the Ranging in up to 33 feet in length From previous studies of cranial remains and bite marks on dinosaur fossil bones, paleontologists have long speculated that the massive beasts preyed on dinosaurs.Now this new study"There are multiple examples of bite marks made by In spite of the genus's name, which means "terror crocodile," they were actually more closely related to alligators. Based on its enormous skull, it looked like neither an alligator nor a crocodile. Its snout was long and broad, but inflated at the front around the nose in a way not seen in any other crocodylian, living or extinct. The reason for its enlarged nose is unknown."It was a strange animal," says co-author Professor Christopher Brochu a palaeontologist, from the University of Iowa. "It shows that crocodylians are not 'living fossils' that haven't changed since the age of dinosaurs. They've evolved just as dynamically as any other group.""It had two large holes are present at the tip of the snout in front of the nose," Dr Cossette says."These holes are unique to
|
Geography
| 2,020 |
August 10, 2020
|
https://www.sciencedaily.com/releases/2020/08/200810113220.htm
|
New global study shows 'best of the last' tropical forests urgently need protection
|
The world's 'best of the last' tropical forests are at significant risk of being lost, according to a paper released today in
|
In the study, the United Nations Development Programme (UNDP), the National Aeronautics and Space Administration (NASA), Wildlife Conservation Society and scientists from eight leading research institutions -- including professor Scott Goetz, research professor Patrick Jantz and research associate Pat Burns of Northern Arizona University' School of Informatics, Computing, and Cyber Systems -- identified significant omissions in international forest conservation strategies. Current global targets focus solely on forest extent and fail to acknowledge the importance of forest intactness, or structural condition, creating a critical gap in action to safeguard ecosystems essential for human and planetary well-being.New targets that recognize forest quality are urgently needed to safeguard the Earth's precious humid tropical forests. Of the 1.9 million hectares of humid tropical forests globally, the study advocated for new protections in 41 percent of these areas, active restoration in 7 percent and reduction of human pressure in 19 percent to promote coordinated strategies to sustain forests of high ecological value."By serving as a convener to bring together the world's best scientists with governments, UNDP plays a critical role in ensuring that cutting-edge research is relevant for the development of key international agreements and implementation at the national level," commented Haoliang Xu, UN Assistant Secretary-General and UNDP Director of Bureau for Policy and Programme Support.Collaborating with UNDP Country Offices and key stakeholders in Brazil, Colombia, Costa Rica, the Democratic Republic of the Congo, Ecuador, Indonesia, Peru, and Viet Nam, researchers mapped the location of high-quality forests using recently developed high-resolution maps of forest structure and human pressure across the global humid tropics.The paper reveals that the Earth's humid tropical forests, only half of which have high ecological integrity, are largely limited to the Amazon and Congo Basins. The vast majority of these forests have no formal protection and, given recent rates of loss, are at significant risk.With the rapid disappearance of these 'best of the last' forests at stake, the paper provides a policy-driven framework for their conservation and restoration, recommending locations to maintain protections, add new protections, restore forest structure, and mitigate human pressure.The coming year is a so-called 'super year' for biodiversity, in which the world will agree on a new deal for nature that will shape global action for the next 30 years. Countries will also have a final chance to revise their contributions to reduce carbon emissions before the Paris Climate Agreement goes into effect. Both these milestones will impact efforts to advance the nature-based Sustainable Development Goals of the 2030 Agenda."The work reported in this paper is the result of a long process assessing the condition of the world's tropical forests," said Goetz, a co-author of the paper. "The breakthrough here was being able to use spaceborne satellite data to provide the first robust estimates of the structural condition of forests in three dimensions, not just forest canopy cover.""Advances in earth observation instruments and methodologies developed by NASA and partner institutions, coupled with the use of incredibly powerful computing systems like NAU's Monsoon and Google Earth Engine, enabled a near-global mapping of tropical forest quality. We synthesized the best available earth observation datasets to map the changing condition of the Earth's tropical forests, finding that only 6.5 percent of the highest quality tropical forests are formally protected. We hope that the conservation strategies proposed as part of this international effort will be a step towards conserving high quality forests and restoring those that have been degraded," said Burns."Every year, research reveals new ways that old, structurally complex forests contribute to biodiversity, carbon storage, water resources, and many other ecosystem services. That we can now map such forests in great detail is an important step forward in efforts to conserve them," said Jantz.
|
Geography
| 2,020 |
August 10, 2020
|
https://www.sciencedaily.com/releases/2020/08/200810113216.htm
|
Past evidence supports complete loss of Arctic sea-ice by 2035
|
A new study, published this week in the journal
|
High temperatures in the Arctic during the last interglacial -- the warm period around 127,000 years ago -- have puzzled scientists for decades. Now the UK Met Office's Hadley Centre climate model has enabled an international team of researchers to compare Arctic sea ice conditions during the last interglacial with present day. Their findings are important for improving predictions of future sea ice change.During spring and early summer, shallow pools of water form on the surface of Arctic sea-ice. These 'melt ponds' are important for how much sunlight is absorbed by the ice and how much is reflected back into space. The new Hadley Centre model is the UK's most advanced physical representation of the Earth's climate and a critical tool for climate research and incorporates sea-ice and melt ponds.Using the model to look at Arctic sea ice during the last interglacial, the team concludes that the impact of intense springtime sunshine created many melt ponds, which played a crucial role in sea-ice melt. A simulation of the future using the same model indicates that the Arctic may become sea ice-free by 2035.Joint lead author Dr Maria Vittoria Guarino, Earth System Modeller at British Antarctic Survey (BAS), says:"High temperatures in the Arctic have puzzled scientists for decades. Unravelling this mystery was technically and scientifically challenging. For the first time, we can begin to see how the Arctic became sea ice-free during the last interglacial. The advances made in climate modelling means that we can create a more accurate simulation of the Earth's past climate, which, in turn gives us greater confidence in model predictions for the future."Dr Louise Sime, the group head of the Palaeoclimate group and joint lead author at BAS, says:"We know the Arctic is undergoing significant changes as our planet warms. By understanding what happened during Earth's last warm period we are in a better position to understand what will happen in the future. The prospect of loss of sea-ice by 2035 should really be focussing all our minds on achieving a low-carbon world as soon as humanly feasible."Dr David Schroeder and Prof Danny Feltham from the University of Reading, who developed and co-led the implementation of the melt pond scheme in the climate model, say:"This shows just how important sea-ice processes like melt ponds are in the Arctic, and why it is crucial that they are incorporated into climate models."The work is funded by NERC, grant number NE/P013279/1 and is part of the TiPES project (
|
Geography
| 2,020 |
August 10, 2020
|
https://www.sciencedaily.com/releases/2020/08/200810103258.htm
|
How fish stocks will change in warming seas
|
New research out today highlights the future effects of climate change on important fish stocks for south-west UK fisheries.
|
The study, which generated future projections of climate impacts on fish in a rapidly warming sea region, suggests changes in the availability and catchability of commercially important Atlantic fish species including Atlantic cod, Dover sole, monkfish and lemon sole. This could have implications for fisheries management, and future fish diets of the British public.The Celtic Sea, English Channel and southern North Sea have experienced significant warming over the past 40 years and further increases in sea temperatures are expected over the coming decades. Projecting future changes can help prepare the fishing industry and management systems for resulting ecological, social and economic effects.The study involved researchers from the University of Exeter, the University of Bristol, the Centre for Environment, Fisheries and Aquaculture Science (Cefas) and the Met Office Hadley Centre. They used computer models to look at how fish abundances may alter by 2090 under a range of future climates. This provided opportunities to not only understand future trends, but how these trends might differ depending on the amount of warming in these seas.Main findings from the study include:Importantly, the results indicate implications not only for the wider ecosystem (e.g. predator prey dynamics or community composition) but that the fishing industry and management systems will likely have to adjust their operations to address these changes. British consumers may need to also adapt their diets into the future to eat species that could benefit under future warming, such as the warm-water species red mullet, Dover sole, john dory and squid.Lead author Dr Katherine Maltby, who undertook the research while at Cefas, said: "Our results show that climate change will continue to affect fish stocks within this sea region into the future, presenting both potential risks but some opportunities that fishers will likely have to adapt to. Consumers can help fishers take advantage of these fishing opportunities by seeking out other fish species to eat and enjoy."Co-author Louise Rutterford, from University of Exeter, said: "We know from working with fishers that warmer water species are appearing in catches more. Bringing together their 'on-the-ground' experiences with studies like ours will help inform future management decisions that enable sustainable exploitation while supporting fishers' adaptation."
|
Geography
| 2,020 |
August 8, 2020
|
https://www.sciencedaily.com/releases/2020/08/200808085754.htm
|
Deep-sea misconceptions cause underestimation of seabed-mining impacts
|
A new publication on the impacts of deep-seabed mining by 13 prominent deep-sea biologists, led by University of Hawai'i at M?noa oceanography professor Craig Smith, seeks to dispel scientific misconceptions that have led to miscalculations of the likely effects of commercial operations to extract minerals from the seabed.
|
The deep sea, ocean depths below 650 feet (200 metres), constitutes more than 90% of the biosphere, harbors the most remote and extreme ecosystems on the planet, and supports biodiversity and ecosystem services of global importance. Interest in deep-seabed mining for copper, cobalt, zinc, manganese and other valuable metals has grown substantially in the last decade and mining activities are anticipated to begin soon."As a team of deep-sea ecologists, we became alarmed by the misconceptions present in the scientific literature that discuss the potential impacts of seabed mining," said Smith. "We found underestimates of mining footprints and a poor understanding of the sensitivity and biodiversity of deep-sea ecosystems, and their potential to recover from mining impacts. All the authors felt it was imperative to dispel misconceptions and highlight what is known and unknown about deep seabed mining impacts."In addition to the impacts of mining on ecosystems in the water above extraction activities, as detailed in another UH-led study published last month, Smith and co-authors emphasize deep-seabed mining impacts on the seafloor, where habitats and communities will be permanently destroyed by mining."The bottom line is that many deep-sea ecosystems will be very sensitive to seafloor mining, are likely to be impacted over much larger scales than predicted by mining interests, and that local and regional biodiversity losses are likely, with the potential for species extinctions," said Smith.The scope of mining impacts from full scale mining, however, will not be well understood until a full-scale mining operation is conducted for years. The geographic scale and ecosystem sensitivities to mining disturbance occurring continuously for decades cannot be simulated or effectively studied at a smaller scale, according to the authors."All the simulations conducted so far do not come close to duplicating the spatial scale, intensity and duration of full-scale mining," said Smith. "Further, the computer models use ecosystem sensitivities derived from shallow-water communities that experience orders of magnitude higher levels turbidity and sediment burial (mining-type perturbations) under natural conditions than the deep-sea communities targeted for mining."Much of the planned deep-seabed mining will be focused in the Pacific Ocean, near Hawai'i, and also near Pacific Island nations. Hawai'i and Pacific Island nations are likely to particularly suffer from any negative environmental impacts, but may benefit economically from deep-seabed mining, creating a need to understand the trade-offs of such mining."Polymetallic-nodule mining (as currently planned) may ultimately impact 500,000 square kilometers of deep seafloor in the Pacific, an area the size of Spain, yielding perhaps the largest environmental footprint of a single extractive activity by humans," said Smith. "Addressing the misconceptions and knowledge gaps related to deep-sea mining is the first step towards effective management of deep-seabed mining."The researchers aim to work closely with regulators and society to help manage deep-seabed mining and emphasize the need to proceed slowly with seabed mining until impacts are fully appreciated.
|
Geography
| 2,020 |
August 8, 2020
|
https://www.sciencedaily.com/releases/2020/08/200808085750.htm
|
Predicting drought in the American West just got more difficult
|
People hoping to get a handle on future droughts in the American West are in for a disappointment, as new USC-led research spanning centuries shows El Niño cycles are an unreliable predictor.
|
Instead, they found that Earth's dynamic atmosphere is a wild card that plays a much bigger role than sea surface temperatures, yet defies predictability, in the wet and dry cycles that whipsaw the western states. The study, published Monday in The findings are significant for water management, agriculture, urban planning and natural resources protection. Recent droughts have claimed many lives and caused damaging crop losses, making drought forecasting a high priority. Meanwhile, the West faces rapid population growth at the same time that forecasts show dry times ahead due to global climate change."The main finding is not terribly hopeful for short-term drought prediction," said Julien Emile-Geay, a study author and associate professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences. "We found that, historically speaking, year-to-year droughts in the western United States were less predictable than previous studies have claimed."New study examines 1,000 years of droughts in the West and beyondEmile-Geay and postdoctoral scholar Michael Erb, who is lead author from USC and now at Northern Arizona University, joined with other scientists at the University of Washington and Columbia University to produce the study.The researchers set out to answer the question: What determines droughts in the West?They examined North American droughts and global conditions spanning more than 1,000 years. Megadroughts, which lasted decades, and dry spells predate the Industrial Revolution, American expansion on the continent or European colonialism. For example, a megadrought in the late 13th century likely contributed to the dispersal of the Anasazi people.The prevailing explanation is that the El Niño-Southern Oscillation plays a key role in these drought episodes. The oscillation is a two-sided coin based on water conditions in the eastern equatorial Pacific Ocean. El Niño conditions occur when sea temperatures in the region are warmer than normal and are associated with wet years in the American Southwest; La Niña conditions occur when water is cooler than normal and are associated with dry years in the Southwest.But the scientists found that rule of thumb didn't jibe well with all drought cycles of the past. While it's true there's a correlation between La Niña and drought, these ocean water conditions accounted for only about 13% of the variability, the study says."La Niña proved to not be the only game in town," Emile-Geay said. "La Niña is part of the game, but not the biggest part."A notable example of this phenomenon occurred in 2015-16, an El Niño year when Southern California did not receive the increased precipitation that was predicted. Instead, the relief came unexpectedly the following year, a La Niña year that should have been drier than normal.What other variables can lead to drought?The scientists also examined other drought influencers, including water temperatures in the Atlantic Ocean and volcanic activity. While those phenomena can influence drought conditions, they are too weak or episodic to explain many droughts.Instead, the study says droughts can originate in the atmosphere. The air around Earth is highly dynamic and influenced by more variables than the ocean alone."The atmosphere creates a lot of variations in moisture supply on its own, and it can cook up droughts all by itself, without being told what to do by the ocean," Emile-Geay said.But while the past is key to the future, it does not hold all the keys. In the future, research says carbon emissions will continue to trap heat and warm the surface, and the West will experience increasingly dry conditions as a result."Our study suggests that the atmosphere will continue to add a strongly unpredictable element to moisture conditions in the southwestern United States, on top of drying induced by global warming," Emile-Geay said. "That is, the Southwest is headed for a drier future overall but with the atmosphere adding a wildcard that may, at times, make things better or worse for the people and ecosystems that depend on that water."The study integrates numerous sources of information spanning centuries to support the findings. The dataset, called the Last Millennium Reanalysis, aggregates climate models, modern temperature measurements and nearly 3,000 climate proxies, such as tree rings, corals, and ice cores. The reanalysis was developed by scientists at USC, the University of Washington and the University of Colorado, with the support of the National Oceanic and Atmospheric Administration. According to the NOAA, the reanalysis aimed to "transform the ways in which the climate community investigates low-frequency climate."
|
Geography
| 2,020 |
August 7, 2020
|
https://www.sciencedaily.com/releases/2020/08/200807111929.htm
|
Florida current is weaker now than at any point in the past century
|
A key component of the Gulf Stream has markedly slowed over the past century -- that's the conclusion of a new research paper in
|
"In the ocean, almost everything is connected," said Christopher Piecuch, an assistant scientist in the Physical Oceanography Department at the Woods Hole Oceanographic Institution (WHOI) and author of the study. "We can use those connections to look at things in the past or far from shore, giving us a more complete view of the ocean and how it changes across space and time."Piecuch, who specializes in coastal and regional sea level change, used a connection between coastal sea level and the strength of near-shore currents to trace the evolution of the Florida Current, which forms the beginning of the Gulf Stream. The Gulf Stream flows north along the Southeast Atlantic Coast of the United States and eventually east into the North Atlantic Ocean, carrying heat, salt, momentum, and other properties that influence Earth's climate. Because nearly continuous records of sea level stretch back more than a century along Florida's Atlantic Coast and in some parts of the Caribbean, he was able to use mathematical models and simple physics to extend the reach of direct measurements of the Gulf Stream to conclude that it has weakened steadily and is weaker now than at any other point in the past 110 years.One of the biggest uncertainties in climate models is the behavior of ocean currents either leading to or responding to changes in Earth's climate. Of these, one of the most important is the Atlantic Meridional Overturning Circulation, or AMOC, which is a large system or "conveyor belt" of ocean currents in the Atlantic that includes the Gulf Stream and that helps regulate global climate. Piecuch's analysis agrees with relationships seen in models between the deeper branches of the AMOC and the Gulf Stream, and it corroborates studies suggesting that the deeper branches of AMOC have slowed in recent years. His method also offers the potential to monitor ocean currents like the Gulf Stream from the coast, complementing existing but difficult-to-maintain moored instruments and expensive research cruises."If we can monitor something over the horizon by making measurements from shore, then that's a win for science and potentially for society," said Piecuch.
|
Geography
| 2,020 |
August 7, 2020
|
https://www.sciencedaily.com/releases/2020/08/200807102332.htm
|
Machine learning research may help find new tungsten deposits in SW England
|
Geologists have developed a machine learning technique that highlights the potential for further deposits of the critical metal tungsten in SW England.
|
Tungsten is an essential component of high-performance steels but global production is strongly influenced by China and western countries are keen to develop alternative sources.The work, published in the leading journal The research applies machine learning to multiple existing datasets to examine the geological factors that have resulted in known tungsten deposits in SW England.These findings are then applied across the wider region to predict areas where tungsten mineralisation is more likely and might have previously been overlooked. The same methodology could be applied to help in the exploration for other metals around the world.Dr Yeomans, a Postdoctoral Research Fellow at the Camborne School of Mines, based at the University of Exeter's Penryn Campus in Cornwall said: "We're really pleased with the methodology developed and the results of this study."SW England is already the focus of UK mineral exploration for tungsten but we wanted to demonstrate that new machine learning approaches may provide additional insights and highlight areas that might otherwise be overlooked."SW England hosts the fourth biggest tungsten deposit in the world (Hemerdon, near Plympton), that resulted in the UK being the sixth biggest global tungsten producer in 2017; the mine is currently being re-developed by Tungsten West Limited.The Redmoor tin-tungsten project, being developed by Cornwall Resources Limited, has also been identified as being a potentially globally significant mineral deposit.The new study suggests that there may be a wider potential for tungsten deposits and has attracted praise from those currently involved in the development of tungsten resources in SW England.James McFarlane, from Tungsten West, said: "Tungsten has only been of economic interest in the last 100 years or so, during which exploration efforts for this critical metal have generally been short-lived."As such is very encouraging to see work that aims to holistically combine the available data to develop a tungsten prospectivity model in an area that has world-class potential."Brett Grist, from Cornwall Resources added: "Our own work has shown that applying modern techniques can reveal world-class deposits in this historic and globally-significant mining district."Dr Yeomans' assertion, that the likelihood of new discoveries of tungsten mineralisation may be enhanced by a high-resolution gravity survey, is something in which we see great potential."Indeed, such a programme could stimulate the new discovery of economically significant deposits of a suite of critical metals, here in the southwest of the UK, for years to come."
|
Geography
| 2,020 |
August 7, 2020
|
https://www.sciencedaily.com/releases/2020/08/200807102330.htm
|
Subpolar marginal seas play a key role in making the subarctic Pacific nutrient-rich
|
A group of researchers from three Japanese universities has discovered why the western subarctic Pacific Ocean, which accounts for only 6 percent of the world's oceans, produces an estimated 26 percent of the world's marine resources.
|
Japan neighbors this ocean area, known for rich marine resources including salmon and trout. The area, located at the termination of the global ocean circulation called the ocean conveyor belt, has one of the largest biological carbon dioxide draw-downs of the world's oceans.The study, led by Hokkaido University, the University of Tokyo and Nagasaki University, showed that water rich in nitrate, phosphate and silicate -- essential chemicals for producing phytoplankton -- is pooled in the intermediate water (from several hundred meters to a thousand meters deep) in the western subarctic area, especially in the Bering Sea basin. Nutrients are uplifted from the deep ocean through the intermediate water to the surface, and then return to the intermediate nutrient pool as sinking particles through the biological production and microbial degradation of organic substances.The intermediate water mixes with dissolved iron that originates in the Okhotsk Sea and is uplifted to the surface -- pivotal processes linking the intermediate water and the surface and that maintain high surface biological productivity. This finding defies the conventional view that nutrients are simply uplifted from the deep ocean to the surface.The study relied on ocean data obtained by a research vessel that surveyed the marginal seas (the Okhotsk Sea and the Bering Sea) where, the group believed, large-scale mixture of seawater occurs due to the interaction of tidal currents with the rough topography. This voyage was made in collaboration with a Russian research team because many of the areas surveyed fall inside Russia's exclusive economic zone. The obtained data was then combined with data collected by Japanese research vessels.Analysis of the data showed that nitrate and phosphate re-produced through microbial degradation of organic substances accumulate in high concentrations in intermediate water in the entire subpolar Pacific region.The researchers also found that the vertical mixing magnitude near the Kuril Islands and the Aleutian Islands is far stronger than that in the surrounding open seas. This study demonstrated that large-scale vertical mixing in the marginal seas breaks the density stratification to mix ocean water, transporting nutrients from the intermediate water to the surface."Our findings should help deepen understanding about the circulation of carbon and nutrients in the ocean and ecological changes caused by climate change," says Associate Professor Jun Nishioka of Hokkaido University, who led the study.
|
Geography
| 2,020 |
August 7, 2020
|
https://www.sciencedaily.com/releases/2020/08/200807093750.htm
|
New Zealand's Southern Alps glacier melt has doubled
|
Glaciers in the Southern Alps of New Zealand have lost more ice mass since pre-industrial times than remains today, according to a new study.
|
Research led by the University of Leeds, in collaboration with the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, mapped Southern Alps ice loss from the end of the Little Ice Age -- roughly 400 years ago -- to 2019.The study found that the rate of ice loss has doubled since glaciers were at their Little Ice Age peak extent. Relative to recent decades, the Southern Alps lost up to 77% of their total Little Ice Age glacier volume.Climate change has had a significant impact on ice loss around the world. Not only do local communities depend on glaciers as sources of fresh water, hydropower and irrigation, but mountain glacier and ice cap melt presently accounts for 25% of global sea-level rise.Rapid changes observed today for mountain glaciers need to be put into a longer-term context to understand global sea-level contributions, regional climate-glacier systems and local landscape evolution.The study, published in the journal The team reconstructed glacier volumes using historical records of glacier outlines, as well as examinations of moraines and trimlines, which are accumulations of glacial debris and clear lines on the side of a valley formed by a glacier, respectively. Moraines and trimlines can indicate former ice margin extent and ice thickness changes through time.By comparing changes in the glacier surface reconstructed during the Little Ice Age peak and the glacier surface in more recent digital elevation models, the study found that ice loss has increased two-fold since the Little Ice Age with a rapid increase in ice volume loss in the last 40 years.Up to 17% of the volume that was present at the Little Ice Age was lost between 1978 and 2019 alone. In 2019, only 12% of ice mass remained in what was formerly the low altitude part of the Little Ice Age glacier region -- also called the ablation zone -- and much of the what used to be ice-covered in the Little Ice Age ablation zone is now completely ice free.Study lead author Dr Jonathan Carrivick, from the School of Geography, said: "These findings quantify a trend in New Zealand's ice loss. The acceleration in the rate of ice mass loss may only get worse as not only climate but also other local effects become more pronounced, such as more debris accumulating on glaciers surfaces and lakes at the bottom of glaciers swell, exacerbating melt."Our results suggest that the Southern Alps has probably already passed the time of 'peak water' or the tipping point of glacier melt supply. Looking forwards, planning must be made for mitigating the decreased runoff to glacier-fed rivers because that affects local water availability, landscape stability and aquatic ecosystems."Co-author Dr Andrew Lorrey is a Principal Scientist based at NIWA who was involved with the study. He says "The long-term ice volume decline, rising snowlines, and rapid disintegration of glaciers across the Southern Alps we have observed is alarming. Photographic evidence that has been regularly collected since the late 1970s show the situation has dramatically worsened since 2010."Our findings provide a conservative baseline for rates of Southern Alps ice volume change since pre-industrial times. They agree with palaeoclimate reconstructions, early historic evidence and instrumental records that show our ice is shrinking from a warming climate."
|
Geography
| 2,020 |
August 6, 2020
|
https://www.sciencedaily.com/releases/2020/08/200806153610.htm
|
Mix of contaminants in Fukushima wastewater, risks of ocean dumping
|
Nearly 10 years after the Tohoku-oki earthquake and tsunami devastated Japan's Fukushima Dai-ichi Nuclear Power Plant and triggered an unprecedented release radioactivity into the ocean, radiation levels have fallen to safe levels in all but the waters closest to the shuttered power plant. Today, fish and other seafood caught in waters beyond all but a limited region have been found to be well within Japan's strict limits for radioactive contamination, but a new hazard exists and is growing every day in the number of storage tanks on land surrounding the power plant that hold contaminated wastewater. An article published August 8 in the journal
|
"We've watched over the past nine-plus years as the levels of radioactive cesium have declined in seawater and in marine life in the Pacific," said Ken Buesseler, a marine chemist at the Woods Hole Oceanographic Institution and author of the new paper. "But there are quite a few radioactive contaminants still in those tanks that we need to think about, some of which that were not seen in large amounts in 2011, but most importantly, they don't all act the same in the ocean."Since 2011, Buesseler has been studying the spread of radiation from Fukushima into and across the Pacific. In June of that year, he mobilized a team of scientists to conduct the first international research cruise to study the early pathways that cesium-134 and -137, two radioactive isotopes of cesium produced in reactors, were taking as they entered the powerful Kuroshio Current off the coast of Japan. He has also built a network of citizen scientists in the U.S. and Canada who have helped monitor the arrival and movement of radioactive material on the Pacific coast of North America.Now, he is more concerned about the more than 1,000 tanks on the grounds of the power plant filling with ground water and cooling water that have become contaminated through contact with the reactors and their containment buildings. Sophisticated cleaning processes have been able to remove many radioactive isotopes and efforts to divert groundwater flows around the reactors have greatly reduced the amount of contaminated water being collected to less than 200 metric tons per day, but some estimates see the tanks being filled in the near future, leading some Japanese officials to suggest treated water should be released into the ocean to free up space for more wastewater.One of the radioactive isotopes that remains at the highest levels in the treated water and would be released is tritium, an isotope of hydrogen is almost impossible to remove, as it becomes part of the water molecule itself. However, tritium has a relatively short half-life, which measures the rate of decay of an isotope; is not absorbed as easily by marine life or seafloor sediments, and produces beta particles, which is not as damaging to living tissue as other forms of radiation. Isotopes that remain in the treated wastewater include carbon-14, cobalt-60, and strontium-90. These and the other isotopes that remain, which were only revealed in 2018, all take much longer to decay and have much greater affinities for seafloor sediments and marine organisms like fish, which means they could be potentially hazardous to humans and the environment for much longer and in more complex ways than tritium."The current focus on tritium in the wastewater holding tanks ignores the presence other radioactive isotopes in the wastewater," said Buesseler. "It's a hard problem, but it's solvable. The first step is to clean up those additional radioactive contaminants that remain in the tanks, and then make plans based on what remains. Any option that involves ocean releases would need independent groups keeping track of all of the potential contaminants in seawater, the seafloor, and marine life. The health of the ocean -- and the livelihoods of countless people -- rely on this being done right."
|
Geography
| 2,020 |
August 6, 2020
|
https://www.sciencedaily.com/releases/2020/08/200806122822.htm
|
First record of invasive shell-boring worm in the Wadden Sea means trouble for oyster
|
In October 2014, the suspicion arose that the parasite worm
|
The worm While the worm might form a big threat to aquaculture farming, it is also likely that aquaculture itself acted as the primary vector of introduction. NIOZ researcher and co-author David Thieltges: 'A large part of the invasive species in the marine ecosystem arrive with the import of commercial species and the transfer of farmed specimens between aquaculture sites.' The worm's favourite host, the Pacific oyster, is traded and cultured globally. By moving the oyster, the worm, though not -intended, becomes an international traveller as well. The researchers, including Thieltges and AWI-scientist Andreas Waser, found the first Once introduced, the further spread of invasive species can continue either via dispersal of larval stages or human-aided secondary vectors such as fouling on ship hulls. This may explain that the worm was also found during sampling at the Mokbaai on Texel, an island without oyster farms. Thieltges underlines, that it is unlikely that the worms found near Texel came from Sylt. 'That they made their way from Sylt to Texel, along almost 500 kilometres of coastline, seems rather unlikely. We think there might be a different origin.'An option would be that larval stages of the worms found in the Dutch Wadden Sea came from Zeeland where there is commercial oyster aquaculture. However, the team still needs to investigate whether the worm is already present in Zeeland as well.' Thieltges: 'Sampling at other places in the Netherlands and in Europe together with genetic research is now needed to establish the origin and distribution of the worm. We don't know its exact origins yet, but we know that it's here and that it is very likely to keep extending its range.'
|
Geography
| 2,020 |
August 6, 2020
|
https://www.sciencedaily.com/releases/2020/08/200806122809.htm
|
Scientists identify missing source of atmospheric carbonyl sulfide
|
Researchers at Tokyo Institute of Technology (Tokyo Tech) report that anthropogenic sources of carbonyl sulfide (OCS), not just oceanic sources, account for much of the missing source of OCS in the atmosphere. Their findings provide better context for estimates of global photosynthesis (taking up CO
|
Carbonyl sulfide (OCS) is the most stable and abundant sulfur-containing gas in the atmosphere. It is derived from both natural and anthropogenic sources and is of key interest to scientists investigating how much carbon dioxide (COUnderstanding the precise OCS budget (the balance of source and sink) is an ongoing challenge. The most critical point of uncertainty related to the OCS budget is its missing source. Lack of observational evidence has so far led to debate about whether the missing OCS source is oceanic or anthropogenic emission.In a new study published in "It's very exciting that we were able to separate anthropogenic and oceanic signals for OCS sources based on sulfur isotope ratios," says Shohei Hattori, an assistant professor at Tokyo Tech and lead author of the study. "These measurements required at least 200 liters of air for each sample measurement. We overcame this challenge by developing a new sampling system, and eventually succeeded in measuring sulfur isotope ratios of the atmospheric OCS."The team found a north-south latitudinal gradient in the "The higher relevance of anthropogenic OCS at mid-to-low latitudes has implications for understanding climate change and stratospheric chemistry in both past and future contexts," says co-author Kazuki Kamezaki.Given that the historical estimation of how much CO"Our sulfur isotopic approach for measuring atmospheric OCS is an important step, but more observations, together with analysis using a chemical transport model, will enable detailed quantitative conclusions," Hattori says.
|
Geography
| 2,020 |
August 6, 2020
|
https://www.sciencedaily.com/releases/2020/08/200806101751.htm
|
Impact of climate change on tropical fisheries would create ripples across the world
|
Tropical oceans and fisheries are threatened by climate change, generating impacts that will affect the sustainable development of both local economies and communities, and regions outside the tropics through 'telecoupling' of human-natural systems, such as seafood trade and distant-water fishing, says a scientific review from UBC and international researchers.
|
Seafood is the most highly traded food commodity globally, with tropical zone marine fisheries contributing more than 50 per cent of the global fish catch, an average of $USD 96 billion annually. Available scientific evidence consistently shows that tropical marine habitats, fish stocks and fisheries are most vulnerable to oceanic changes associated with climate change. However, the scientific review highlights that telecoupling, or linkages between distant human-natural systems, could generate cascades of climate change impacts from the tropics that propagate to other 'extra-' tropical natural systems and human communities globally."Telecoupling interactions between two or more linked areas over distance between tropical fisheries and elsewhere include distant-water fishing, the international seafood supply chain, transboundary fisheries resources and their governance would allow benefits derived from tropical fisheries to transfer to the people in the extratropical regions," said Vicky Lam, lead author and research associate in the UBC's Institute for the Oceans and Fisheries. "Although these linkages could enable the flow of benefits, including food, livelihoods and government revenue, from tropical fisheries to extratropical locations, their dependence on tropical fisheries also exposes them to the negative consequences of climate change in tropical regions. The effects of climate change on tropical fisheries also affect the profitability and employment opportunities of fish-processing industries in extratropical regions.""Pacific Island countries and territories, for example, are expected to see a redistribution of skipjack and yellowfin tuna -- their two most exported fish species -- that could see decreased catches of between 10 and 40 per cent by 2050 in many countries such as Palau and the Solomon Islands, while catches are expected to increase by 15 to 20 per cent in Kiribati and the Cook Islands. This will have a tremendous effect on the economies of these small island developing states," said Rashid Sumaila, co-author and professor at UBC's Institute for the Oceans and Fisheries and School of Public Policy and Global Affairs. "There are similar projections in African nations, where climate-related changes are expected to decrease the value of landed catch by approximately 20 per cent by 2050, as well as reduce fisheries-related jobs by 50 per cent."To reduce the effect of climate change on the benefits derived from tropical fisheries, both locally and in extra-tropical regions, the root causes of climate-driven problems in tropical fisheries need to be recognized and rectified. Effective and practical adaptation and mitigation solutions with stakeholder commitment and involvement, as well as supporting policies, are therefore necessary in the tropics."We already see that there are close linkages between the tropical regions and the extra-tropical nations through trade and distant-water fishing" said William Cheung, co-author and professor at UBC's Institute for the Oceans and Fisheries. "Solving climate change impacts in the tropics will benefit the whole world; this provides an additional argument for non-tropical countries to support climate mitigation and adaptation in tropical countries."
|
Geography
| 2,020 |
August 5, 2020
|
https://www.sciencedaily.com/releases/2020/08/200805160938.htm
|
An iconic Native American stone tool technology discovered in Arabia
|
A new study led by archaeologists from the CNRS, the Inrap, the Ohio State University and the Max Planck Institute for the Science of Human History, reports on fluted points from the archaeological sites of Manayzah in Yemen and Ad-Dahariz in Oman. Fluted stone tools are a distinctive, technologically advanced form of projectile points, including spearheads and arrowheads. Fluting is a specific technique that involves the extraction of an elongated flake along the length of a projectile point, leaving a distinctive groove or depression at the base of the spearhead or arrowhead.
|
Fluting is a distinct technological tradition invented by early human cultures that spread across the Americas. Fluted point technology is very well known in North America, evidenced by finds across the continent dating from 13,000 to 10,000 years ago. As lead author Dr. Rémy Crassard of the CNRS notes, "Until the early 2000s, these fluted points were unknown elsewhere on the planet. When the first isolated examples of these objects were recognized in Yemen, and more recently in Oman, we recognized that there could be huge implications."The sites of Manayzah and Ad-Dahariz yielded dozens of fluted points. The Arabian examples date to the Neolithic period, about 8,000 to 7,000 years ago, at least two thousand years later than the American examples. As Professor Petraglia of the Max Planck explains, "Given their age and the fact that the fluted points from America and Arabia are separated by thousands of kilometers, there is no possible cultural connection between them. This is then a clear and excellent example of cultural convergence, or independent invention in human history."The new PLOS ONE article carefully examines the fluted points found in south Arabia. Detailed technological analysis, backed up by stone tool experiments and replication by an expert modern flintknapper, illustrate the similarities between the American and Arabian fluting procedures.In addition to the similarities, the authors of the new study also investigated the contrasts between the technologies of the two regions. Technological differences were apparent in the nature and location of the flute. The authors emphasize that the 'fluting method' was likely a mental conceptualization of stone tool manufacture, more than just a technical way to produce a projectile and hafting zone. Whereas the apparent function of fluting in the Americas is to facilitate hafting, or attaching the point to a shaft, most of the Arabian fluted points do not have hafting as a functional final aim. The fluting concept and the method itself are the same in both American and Arabia, yet the final aim of fluting appears to be different.Arabian and American fluted point technologies were highly specialized stone tool production methods. The PLOS ONE study of Arabian fluting technology demonstrates that similar innovations and inventions were developed under different circumstances and that such highly-skilled and convergent production methods can have different anthropological implications. As discussed in the article, Professor McCorriston argues that "fluting in Arabia was used as a display of skill, rather than serving a purely functional purpose such as hafting, as is more widely accepted in the Americas."In Arabian prehistory, southern Arabia experienced developments of local origin, with multiple examples of inventions and innovations not culturally transmitted by outside traditions. The fluting method is then a hallmark of this indigenous development in the south Arabian Neolithic.
|
Geography
| 2,020 |
August 5, 2020
|
https://www.sciencedaily.com/releases/2020/08/200805124046.htm
|
Ocean heatwaves dramatically shift habitats
|
Marine heatwaves across the world's oceans can displace habitat for sea turtles, whales, and other marine life by 10s to thousands of kilometers. They dramatically shift these animals' preferred temperatures in a fraction of the time that climate change is expected to do the same, new research shows.
|
To measure that temporary dislocation of ocean surface temperatures, which can in turn drive ecological changes, NOAA scientists have now introduced a new metric called "thermal displacement." A research paper describing the changes and the means of measuring them was published in the journal Research scientist Michael Jacox of NOAA Fisheries' Southwest Fisheries Science Center called it a powerful new way of looking at marine heatwaves."When the environment changes, many species move," Jacox said. "This research helps us understand and measure the degree of change they may be responding to."Scientists have typically characterized marine heatwaves based on how much they increase sea surface temperatures, and for how long. Such local warming particularly affects stationary organisms such as corals. In contrast, thermal displacement measures how far mobile species must move to track ocean surface temperatures.The extent of thermal displacement caused by marine heatwaves may not necessarily correspond to their intensity.Thermal displacement depends on the sea surface temperature gradient, the rate at which temperature changes across the ocean. If a heatwave warms an area of ocean, fish, turtles, whales, and other species may have to travel great distances if the temperature gradient is weak, but not if the gradient is strong."It may give us an idea how the ecosystem may change in the future," said Michael Alexander, research meteorologist at NOAA's Physical Sciences Laboratory and a coauthor of the new research. The changes may have implications for coastal communities if commercial fish species shift. Fishermen would have to travel hundreds of miles farther to reach them, he said.Changing Temperatures Highlight Management QuestionsFor example, a 2012 marine heatwave in the northwest Atlantic pushed commercial species such as squid and flounder hundreds of miles northward. At the same time it contributed to a lobster boom that led to record landings and a collapse in price."Given the complex political geography of the United States' Eastern Seaboard, this event highlighted management questions introduced by marine heatwave-driven shifts across state and national lines," the scientists wrote."While these management issues are often discussed in the context of climate change, they are upon us now," the scientists wrote. "Modern day marine heatwaves can induce thermal displacements comparable to those from century-scale warming trends, and while these temperature shifts do not solely dictate species distributions, they do convey the scale of potential habitat disruption."A 2014-2015 Pacific marine heatwave known as "the Blob," shifted surface temperatures more than 700 kilometers, or more than 400 miles, along the West Coast of the United States and in the Gulf of Alaska. That moved the prey of California sea lions farther from their rookeries in the Channel Islands off Southern California. This left hundreds of starving sea lion pups to strand on beaches.Across the world's oceans, the average long-term temperature shift associated with ocean warming has been estimated at just over 20 kilometers, about 13 miles, per decade. By comparison, marine heatwaves have displaced temperatures an average of approximately 200 kilometers, roughly 120 miles, in a matter of months. In effect, marine heatwaves are shifting ocean temperatures at similar scales to what is anticipated with climate change -- but in much shorter time frames.The research was supported by funding from the NOAA Climate Program Office's Coastal and Ocean Climate Applications program and Modeling, Analysis, Predictions, and Projections program and the NOAA Fisheries Office of Science and Technology.
|
Geography
| 2,020 |
August 5, 2020
|
https://www.sciencedaily.com/releases/2020/08/200805124016.htm
|
Algal symbiosis could shed light on dark ocean
|
New research has revealed a surprise twist in the symbiotic relationship between a type of salamander and the alga that lives inside its eggs. A new paper in
|
Plants and animals sometimes partner up in symbiotic relationships that benefit both, such as corals that provide a protective environment for algae that live inside them, and receive oxygen and nutrients from the algae in return. Originally, scientists believed that the salamander eggs and algae may be helping one another by exchanging sugar molecules -- but a series of laboratory experiments showed molecular biologist John Burns and his colleagues Solange Duhamel at the University of Arizona and Ryan Kerney at Gettysburg College that this was not the case. Burns is the newest senior research scientist at Bigelow Laboratory for Ocean Sciences, and much of his research explores how unusual situations in cell biology can inform understanding of the way larger systems function."Direct associations between algae and vertebrate animals are rare, and so one of the big questions has always been why this symbiosis exists in the first place," Burns said. "Learning about the chemical dialog between the algae and salamander eggs is essential for understanding their relationship, and implications for other symbioses."Algae and other plants remove carbon dioxide from their surroundings for use in key biochemical processes, such as synthesizing essential molecules. Animals must assimilate, or "fix," carbon to excrete as the waste product urea. Animals also fix small amounts of carbon for use in other biochemical pathways -- including, the researchers discovered, spotted salamander embryos.Burns believes that this ability could provide a "shortcut" that makes biochemical processes in the embryos more efficient. All animals must synthesize and process dozens of molecules in order to conduct the processes necessary for life, like the conversion of food into energy and waste products. Carbon is one of the essential ingredients in these processes, and being able to quickly incorporate an additional carbon atom could confer a handy evolutionary advantage."Research today often doesn't account for the fact that animals can fix small amounts of carbon," Burns said. "Understanding that plants and animals can actually compete for carbon is one key to understanding what really happens in these symbiotic relationships."Though algae and plants require light to fix carbon, the salamander eggs do not. Burns believes that the processes taking place in the eggs may be similar to those happening in some ocean microbes, and that they could serve as a useful parallel for an often-overlooked type of carbon fixation.Previous research has shown that carbon fixation continues in the ocean even during the dark of night. It also happens in the deep ocean, beyond the reach of the sun -- but it has never been clear how much of an impact these processes have on a global scale."Learning more about these chemical dialogs could teach us about the players in dark carbon fixation, and help us begin understanding how big an effect this has on the global ocean," Burns said. "This research into the minute world inside a salamander egg can prompt us to ask new questions about the effects of competition for inorganic carbon, particularly during symbioses, on entire food webs."
|
Geography
| 2,020 |
August 5, 2020
|
https://www.sciencedaily.com/releases/2020/08/200805110120.htm
|
Blanket of rock debris offers glaciers more protection from climate change than previously known
|
A new study which provides a global estimate of rock cover on the Earth's glaciers has revealed that the expanse of rock debris on glaciers, a factor that has been ignored in models of glacier melt and sea level rise, could be significant.
|
The Northumbria University study, which has been published in As glaciers shrink, their surrounding mountain slopes become exposed and eroded rock debris slides down and accumulates on glacier surfaces. This debris forms a protective layer that can be many metres thick, reducing the rate at which the ice below melts. Although the effects of this protective cover are known, it has never been carefully mapped until now, and so has not been included in global glacier models.As well as revealing where rock debris is located on Earth's glaciers, the researchers also found and corrected key errors within the Randolph Glacier Inventory -- a global inventory of glacier outlines on which hundreds of studies are based.Using Landsat imagery, the research team from Northumbria University's Department of Geography and Environmental Sciences and the Swiss Federal Research Institute WSL spent three years painstakingly examining and manually verifying more than 923,000 square kilometres of glacier worldwide.The exercise allowed them to analyse the debris cover on a global-, regional-, as well as individual glacier-scale and created the world's first baseline dataset of glaciers in their current state.They found more than 29,000 square kilometres of the world's mountain glacier area is covered in rock debris -- an area equivalent to almost 500 Manhattan Islands.Lead researcher Sam Herreid undertook the study for his PhD at Northumbria University and is now believed to be the only person who has examined every glacier on Earth, manually correcting the Randolph Glacier Inventory and bringing a level of consistency that has never before been present in a global glacier dataset.He explained: "The structure of the debris cover of each glacier is unique and sensitive to climate, but until now, global glacier models have omitted debris cover from their forecasts of how glaciers respond to a changing climate."We now know that debris cover is present on almost half of Earth's glaciers, with 7.3% of the world's total mountain glacier area being debris covered."When we consider that much of this debris cover is located at the terminus, or toe, of a glacier where melt would usually be at its highest, this percentage becomes particularly important with respect to predicting future water resources and sea level rise."The study also uncovered errors within the Randolph Glacier Inventory, finding an error rate of 3.3%. One of their findings revealed that 10,000 square kilometres of mapped glacier area was not actually glacier, but rather bedrock or vegetated ground that was either incorrectly mapped previously or glacier area that has since melted away.This, combined with the melt reduction from debris insulating the ice below, means that all past global glacier models based on the Inventory are likely to have overestimated the true volume of glacier melt, run off and subsequent contribution to global sea level rise.They described the 10.6% of glacier area that requires an updated approach to estimating melt as "an alarmingly high number" and said that their work provides a key dataset for revising, and likely lowering, the glacier contribution to sea level rise.The team also devised a way to analyse how the world's debris-covered glaciers will evolve over the coming centuries.By comparing the many states of glaciers present on Earth today, from those considered to be 'young' and icy in Greenland, to 'old' and rock covered in the Himalaya, they were able to piece together a conceptual timeline which they believe outlines how a glacier might evolve in the future.Their timeline reveals that many glaciers are at the older end of the spectrum and can therefore be considered to be on the decline.Co-author Francesca Pellicciotti of the Swiss Federal Research Institute WSL and an Associate Professor at Northumbria University, explained: "The upper levels of the glaciers are constantly accumulating snow and will always be debris free, so we looked only at the lower levels of glaciers which is where rock debris can accumulate."Ice melts and flows away as water, but the rocks do not, and accumulate at the surface. Changes in the rate of mountain erosion as well as glacier changes in a warming climate will affect the size and shape of the rock layer at the surface of a glacier at any one time."Although we can't say exactly what year a glacier will evolve to a certain state, say, a state where it is almost entirely covered in rocks, we were able to place each glacier on a conceptual timeline and learn roughly how far along this line each glacier is to becoming almost entirely covered in rocks.She added: "We found that the bulk of glaciers that have a debris cover today are beyond a peak debris cover formation state and are trending closer to the "old" Himalayan glaciers that might not be around for much longer."From a climate change perspective this is one more indication of the toll a warming climate is having on Earth's glaciers. However, we now have a benchmark measurement of debris cover for all of Earth's glaciers and new tools to monitor and predict the rate of changes couple to a warming climate."
|
Geography
| 2,020 |
August 5, 2020
|
https://www.sciencedaily.com/releases/2020/08/200805110118.htm
|
Lava tubes on Mars and the Moon are so wide they can host planetary bases
|
Researchers at the Universities of Bologna and Padua studied the subsurface cavities that lava created underground on Mars and the Moon. These cavities can shield from cosmic radiation.
|
The international journal This study involved the Universities of Bologna and Padua and its coordinators are Francesco Sauro and Riccardo Pozzobon. Francesco Sauro is a speleologist and head of the ESA programmes CAVES and PANGAEA, he is also a professor at the Department of Biological, Geological, and Environmental Sciences at the University of Bologna. Riccardo Pozzobon is a planetary geologist at the Department of Geosciences of the University of Padua."We can find lava tubes on planet Earth, but also on the subsurface of the Moon and Mars according to the high-resolution pictures of lava tubes' skylights taken by interplanetary probes. Evidence of lava tubes was often inferred by observing linear cavities and sinuous collapse chains where the galleries cracked," explains Francesco Sauro. "These collapse chains represent ideal gateways or windows for subsurface exploration. The morphological surface expression of lava tubes on Mars and the Moon is similar to their terrestrial counterpart. Speleologists thoroughly studied lava tubes on Earth in Hawaii, Canary Islands, Australia and Iceland.""We measured the size and gathered the morphology of lunar and Martian collapse chains (collapsed lava tubes), using digital terrain models (DTMs), which we obtained through satellite stereoscopic images and laser altimetry taken by interplanetary probes," reminds Riccardo Pozzobon. "We then compared these data to topographic studies about similar collapse chains on the Earth's surface and to laser scans of the inside of lava tubes in Lanzarote and the Galapagos. These data allowed to establish a restriction to the relationship between collapse chains and subsurface cavities that are still intact."Researchers found that Martian and lunar tubes are respectively 100 and 1,000 times wider than those on Earth, which typically have a diameter of 10 to 30 meters. Lower gravity and its effect on volcanism explain these outstanding dimensions (with total volumes exceeding 1 billion of cubic meters on the Moon).Riccardo Pozzobon adds: "Tubes as wide as these can be longer than 40 kilometres, making the Moon an extraordinary target for subsurface exploration and potential settlement in the wide protected and stable environments of lava tubes. The latter are so big they can contain Padua's entire city centre.""What is most important is that, despite the impressive dimension of the lunar tubes, they remain well within the roof stability threshold because of a lower gravitational attraction," explains Matteo Massironi, who is professor of Structural and Planetary Geology at the Department of Geosciences of the University of Padua. "This means that the majority of lava tubes underneath the maria smooth plains are intact. The collapse chains we observed might have been caused by asteroids piercing the tube walls. This is what the collapse chains in Marius Hills seem to suggest. From the latter, we can get access to these huge underground cavities."Francesco Sauro concludes: "Lava tubes could provide stable shields from cosmic and solar radiation and micrometeorite impacts which are often happening on the surfaces of planetary bodies. Moreover, they have great potential for providing an environment in which temperatures do not vary from day- to night-time. Space agencies are now interested in planetary caves and lava tubes, as they represent a first step towards future explorations of the lunar surface (see also NASA's project Artemis) and towards finding life (past or present) in Mars subsurface."Researchers also point out how this study opens up to a completely new perspective in planetary exploration, which is increasingly focusing on the subsurface of Mars and the Moon."In autumn 2019, ESA called up universities and industries with a campaign seeking ideas for developing technologies for lunar caves exploration. They are specifically looking for systems that would land on the lunar surface to operate missions exploring lunar tubes," clarifies Unibo professor Jo De Waele, who is one of the authors of the study and a speleologist. "Since 2012, in collaboration with some European universities including Bologna and Padua, ESA has been carrying out two training programmes for astronauts focusing on the exploration of underground systems (CAVES) and planetary geology (PANGAEA). These programmes include lava tubes on the island of Lanzarote. So far, 36 astronauts from five space agencies have received training in cave hiking; moreover, six astronauts and four mission and operation specialists have received geological field training."The title of this study is "Lava tubes on Earth, Moon and Mars: A review on their size and morphology revealed by comparative planetology" and it was published in the journal
|
Geography
| 2,020 |
August 4, 2020
|
https://www.sciencedaily.com/releases/2020/08/200804111444.htm
|
How the seafloor of the Antarctic Ocean is changing - and the climate is following suit
|
The glacial history of the Antarctic is currently one of the most important topics in climate research. Why? Because worsening climate change raises a key question: How did the ice masses of the southern continent react to changes between cold and warm phases in the past, and how will they do so in the future? A team of international experts, led by geophysicists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), has now shed new light on nine pivotal intervals in the climate history of the Antarctic, spread over 34 million years, by reconstructing the depth of the Southern Ocean in each one. These new maps offer insights into e.g. the past courses of ocean currents, and show that, in past warm phases, the large ice sheets of East Antarctica reacted to climate change in a similar way to how ice sheets in West Antarctica are doing so today. The maps and the freely available article have just been released in the online journal
|
The Southern Ocean is one of the most important pillars of the Earth's climate system. Its Antarctic Circumpolar Current, the most powerful current on the planet, links the Pacific, Atlantic and Indian Oceans, and has effectively isolated the Antarctic continent and its ice masses from the rest of the world for over 30 million years. Then and now, ocean currents can only flow where the water is sufficiently deep and there are no obstacles like land bridges, islands, underwater ridges and plateaus blocking their way. Accordingly, anyone seeking to understand the climate history and glacial history of the Antarctic needs to know exactly what the depth and surface structures of the Southern Ocean's floor looked like in the distant past.Researchers around the globe can now find this information in new, high-resolution grid maps of the ocean floor and data-modelling approaches prepared by a team of international experts led by geoscientists from the AWI, which cover nine pivotal intervals in the climate history of the Antarctic. "In the course of the Earth's history, the geography of the Southern Ocean has constantly changed, as continental plates collided or drifted apart, ridges and seamounts formed, ice masses shoved deposited sediments across the continental shelves like bulldozers, and meltwater transported sediment from land to sea," says AWI geophysicist and co-author Dr Karsten Gohl. Each process changed the ocean's depth and, in some cases, the currents. The new grid maps clearly show how the surface structure of the ocean floor evolved over 34 million years -- at a resolution of ca. 5 x 5 kilometres per pixel, making them 15 times more precise than previous models.In order to reconstruct the past water depths, the experts gathered geoscientific field data from 40 years of Antarctic research, which they then combined in a computer model of the Southern Ocean's seafloor. The basis consisted of seismic profiles gathered during over 150 geoscientific expeditions and which, when put end-to-end, cover half a million kilometres. In seismic reflection, sound waves are emitted, penetrating the seafloor to a depth of several kilometres. The reflected signal is used to produce an image of the stratified sediment layers below the surface -- a bit like cutting a piece of cake, which reveals the individual layers. The experts then compared the identified layers with sediment cores from the corresponding regions, which allowed them to determine the ages of most layers. In a final step, they used a computer model to 'turn back time' and calculate which sediment deposits were already present in the Southern Ocean at specific intervals, and to what depths in the seafloor they extended in the respective epochs.They applied this approach to nine key intervals in the Antarctic's climate history, including e.g. the warm phase of the early Pliocene, five million years ago, which is widely considered to be a potential template for our future climate. Back then the world was 2 to 3 degrees Celsius warmer on average than today, partly because the carbon dioxide concentration in the atmosphere was as high as 450 ppm (parts per million). The IPCC (IPCC Special Report on the Ocean and Cryosphere in a Changing Climate, 2019) has cited this concentration as the best-case scenario for the year 2100; in June 2019 the level was 415 ppm. Back then, the Antarctic ice shelves now floating on the ocean had most likely completely collapsed. "Based on the sediment deposits we can tell, for example, that in extremely warm epochs like the Pliocene, the large ice sheets in East Antarctica reacted in a very similar way to what we're currently seeing in ice sheets in West Antarctica," reports Dr Katharina Hochmuth, the study's first author and a former AWI geophysicist, who is now conducting research at the University of Leicester, UK.Accordingly, the new maps provide data on important climatic conditions that researchers around the world need in order to accurately simulate the development of ice masses in their ice-sheet and climate models, and to produce more reliable forecasts. Researchers can also download the corresponding datasets from the AWI's Earth system database PANGAEA.In addition to researchers from the AWI, experts from the following institutions took part in the study: (1) All Russia Scientific Research Institute for Geology and Mineral Resources of the Ocean, St. Petersburg, Russia; (2) St. Petersburg State University, Russia; (3) University of Tasmania, Australia; (4) GNS Science, Lower Hutt, New Zealand; and (5) the National Institute of Oceanography and Applied Geophysics, Italy.The grid maps depict the geography of the Southern Ocean in the following key intervals in the climate history and glacial history of the Antarctic:(2) 27 million years ago -- the early Oligocene;(3) 24 million years ago -- transition from the Oligocene to the Miocene;(4) 21 million years ago -- the early Miocene;(5) 14 million years ago -- the mid-Miocene, Miocene Climatic Optimum (mean global temperature ca. 4 degrees Celsius warmer than today; high carbon dioxide concentration in the atmosphere);(6) 10.5 million years ago -- the late Miocene, major continental-scale glaciation;(7) 5 million years ago -- the early Pliocene (mean global temperature ca. 2 -- 3 degrees Celsius warmer than today; high carbon dioxide concentration in the atmosphere);(8) 2.65 million years ago -- transition from the Pliocene to the Pleistocene;(9) 0.65 million years ago -- the Pleistocene.The data on sediment cores was gathered in geoscientific research projects conducted in connection with the Deep Sea Drilling Project (DSDP), Ocean Drilling Program (ODP), Integrated Ocean Drilling Program, and International Ocean Discovery Program (IODP).
|
Geography
| 2,020 |
August 3, 2020
|
https://www.sciencedaily.com/releases/2020/08/200803120154.htm
|
Early Mars was covered in ice sheets, not flowing rivers, researchers say
|
A large number of the valley networks scarring Mars's surface were carved by water melting beneath glacial ice, not by free-flowing rivers as previously thought, according to new UBC research published today in
|
To reach this conclusion, lead author Anna Grau Galofre, former PhD student in the department of earth, ocean and atmospheric sciences, developed and used new techniques to examine thousands of Martian valleys. She and her co-authors also compared the Martian valleys to the subglacial channels in the Canadian Arctic Archipelago and uncovered striking similarities."For the last 40 years, since Mars's valleys were first discovered, the assumption was that rivers once flowed on Mars, eroding and originating all of these valleys," says Grau Galofre. "But there are hundreds of valleys on Mars, and they look very different from each other. If you look at Earth from a satellite you see a lot of valleys: some of them made by rivers, some made by glaciers, some made by other processes, and each type has a distinctive shape. Mars is similar, in that valleys look very different from each other, suggesting that many processes were at play to carve them."The similarity between many Martian valleys and the subglacial channels on Devon Island in the Canadian Arctic motivated the authors to conduct their comparative study. "Devon Island is one of the best analogues we have for Mars here on Earth -- it is a cold, dry, polar desert, and the glaciation is largely cold-based," says co-author Gordon Osinski, professor in Western University's department of earth sciences and Institute for Earth and Space Exploration.In total, the researchers analyzed more than 10,000 Martian valleys, using a novel algorithm to infer their underlying erosion processes. "These results are the first evidence for extensive subglacial erosion driven by channelized meltwater drainage beneath an ancient ice sheet on Mars," says co-author Mark Jellinek, professor in UBC's department of earth, ocean and atmospheric sciences. "The findings demonstrate that only a fraction of valley networks match patterns typical of surface water erosion, which is in marked contrast to the conventional view. Using the geomorphology of Mars' surface to rigorously reconstruct the character and evolution of the planet in a statistically meaningful way is, frankly, revolutionary."Grau Galofre's theory also helps explain how the valleys would have formed 3.8 billion years ago on a planet that is further away from the sun than Earth, during a time when the sun was less intense. "Climate modelling predicts that Mars' ancient climate was much cooler during the time of valley network formation," says Grau Galofre, currently a SESE Exploration Post-doctoral Fellow at Arizona State University. "We tried to put everything together and bring up a hypothesis that hadn't really been considered: that channels and valleys networks can form under ice sheets, as part of the drainage system that forms naturally under an ice sheet when there's water accumulated at the base."These environments would also support better survival conditions for possible ancient life on Mars. A sheet of ice would lend more protection and stability of underlying water, as well as providing shelter from solar radiation in the absence of a magnetic field -- something Mars once had, but which disappeared billions of years ago.While Grau Galofre's research was focused on Mars, the analytical tools she developed for this work can be applied to uncover more about the early history of our own planet. Jellinek says he intends to use these new algorithms to analyze and explore erosion features left over from very early Earth history."Currently we can reconstruct rigorously the history of global glaciation on Earth going back about a million to five million years," says Jellinek. "Anna's work will enable us to explore the advance and retreat of ice sheets back to at least 35 million years ago -- to the beginnings of Antarctica, or earlier -- back in time well before the age of our oldest ice cores. These are very elegant analytical tools."
|
Geography
| 2,020 |
July 31, 2020
|
https://www.sciencedaily.com/releases/2020/07/200731180717.htm
|
Cooling of Earth caused by eruptions, not meteors
|
Ancient sediment found in a central Texas cave appears to solve the mystery of why the Earth cooled suddenly about 13,000 years ago, according to a research study co-authored by a Texas A&M University professor.
|
Michael Waters, director of The Center for The Study of the First Americans and Distinguished Professor at Texas A&M University, and colleagues from Baylor University and the University of Houston have had their work published in Some researchers believed the event -- which cooled the Earth by about 3 degrees Centigrade, a huge amount -- was caused by an extraterrestrial impact with the Earth, such as a meteor collision.But Waters and the team found that the evidence left in layers of sediment in Hall's Cave were almost certainly the result of volcanic eruptions.Waters said that Hall's Cave, located in the Texas hill country, has a sediment record extending over 20,000 years and he first began researching the cave in 2017."It is an exceptional record that offers a unique opportunity for interdisciplinary cooperation to investigate a number of important research questions," he said."One big question was, did an extraterrestrial impact occur near the end of the last ice age, about 13,000 years ago as the ice sheets covering Canada were melting, and cause an abrupt cooling that thrust the northern hemisphere back into the ice age for an extra 1,200 years?"Waters and the team found that within the cave are layers of sediment, first identified by Thomas Stafford (Stafford Research Laboratories, Colorado), that dated to the time of the proposed impact that could answer the question and perhaps even identify the trigger that started the ancient cold snap.The event also likely helped cause the extinction of large mammals such as mammoth, horse and camel that once roamed North America."This work shows that the geochemical signature associated with the cooling event is not unique but occurred four times between 9,000 and 15,000 years ago," said Alan Brandon, professor of geosciences at University of Houston and head of the research team."Thus, the trigger for this cooling event didn't come from space. Prior geochemical evidence for a large meteor exploding in the atmosphere instead reflects a period of major volcanic eruptions."I was skeptical," Brandon said. "We took every avenue we could to come up with an alternative explanation, or even avoid, this conclusion. A volcanic eruption had been considered one possible explanation but was generally dismissed because there was no associated geochemical fingerprint."After a volcano erupts, the global spread of aerosols reflects incoming solar radiation away from Earth and may lead to global cooling post eruption for one to five years, depending on the size and timescales of the eruption, the team said."The Younger Dryas, which occurred about 13,000 years ago, disrupted distinct warming at the end of the last ice age," said co-author Steven Forman, professor of geosciences at Baylor.The Earth's climate may have been at a tipping point at the end of Younger Dryas, possibly from the ice sheet discharge into the North Atlantic Ocean, enhanced snow cover and powerful volcanic eruptions that may have in combination led to intense Northern Hemisphere cooling, Forman said."This period of rapid cooling coincides with the extinction of a number of species, including camels and horses, and the appearance of the Clovis archaeological tradition," said Waters.Brandon and fellow University of Houston scientist Nan Sun completed the isotopic analysis of sediments collected from Hall's Cave. They found that elements such as iridium, ruthenium, platinum, palladium and rhenium were not present in the correct proportions, meaning that a meteor or asteroid could not have caused the event."The isotope analysis and the relative proportion of the elements matched those that were found in previous volcanic gases," said Sun, lead author of the report.Volcanic eruptions cause their most severe cooling near the source, usually in the year of the eruption, with substantially less cooling in the years after the eruption, the team said.The Younger Dryas cooling lasted about 1,200 years, "so a sole volcanic eruptive cause is an important initiating factor, but other Earth system changes, such as cooling of the oceans and more snow cover were needed to sustain this colder period, "Forman said.Waters added that the bottom line is that "the chemical anomalies found in sediments dating to the beginning of the Younger Dryas are the result of volcanism and not an extraterrestrial impact."
|
Geography
| 2,020 |
July 31, 2020
|
https://www.sciencedaily.com/releases/2020/07/200731145143.htm
|
California's sinking coastal hotspots
|
A majority of the world population lives on low lying lands near the sea, some of which are predicted to submerge by the end of the 21st century due to rising sea levels.
|
The most relevant quantity for assessing the impacts of sea-level change on these communities is the relative sea-level rise -- the elevation change between the Earth's surface height and sea surface height. For an observer standing on the coastland, relative sea-level rise is the net change in the sea level, which also includes the rise and fall of the land beneath observer's feet.Now, using precise measurements from state-of-the-art satellite-based interferometric synthetic aperture radar (InSAR) that can detect the land surface rise and fall with millimeter accuracy, an Arizona State University research team has, for the first time, tracked the entire California coast's vertical land motion.They've identified local hotspots of the sinking coast, in the cities of San Diego, Los Angeles, Santa Cruz and San Francisco, with a combined population of 4 to 8 million people exposed to rapid land subsidence, who will be at a higher flooding risk during the decades ahead of projected sea-level rise."We have ushered in a new era of coastal mapping at greater than 1,000 fold higher detail and resolution than ever before," said Manoochehr Shirzaei, who is the principal investigator of the NASA-funded project. "The unprecedented detail and submillimeter accuracy resolved in our vertical land motion dataset can transform the understanding of natural and anthropogenic changes in relative sea-level and associated hazards."The results were published in this week's issue of The research team included graduate student and lead author Em Blackwell, and faculty Manoochehr Shirzaei, Chandrakanta Ojha and Susanna Werth, all from the ASU School of Earth and Space Exploration (Werth has a dual appointment in the School of Geography and Urban Planning).Em Blackwell had a keen interest in geology, and as Blackwell began graduate school, the applications of InSAR drew them to pursue this project. InSAR uses radar to measure the change in distance between the satellite and ground surface, producing highly accurate deformation maps of the Earth's surface at 10s m resolution over 100s km spatial extent.Land subsidence can occur due to natural and anthropogenic processes or a combination of them. The natural processes comprise tectonics, glacial isostatic adjustment, sediment loading, and soil compaction. The anthropogenic causes include groundwater extraction and oil and gas production.As of 2005, approximately 40 million people were exposed to a 1 in 100-year coastal flooding hazard, and by 2070 this number will grow more than threefold. The value of property exposed to flooding will increase to about 9% of the projected global Gross Domestic Product, with the U.S., Japan, and the Netherlands being the countries with the most exposure. These exposure estimates often rely only on projections of global average sea level rise and do not account for vertical land motion.The study measured the entire 1350-kilometer long coast of California from 2007-2018, compiling 1000s of satellite images over time, used for making a vertical land motion map with 35-million-pixel at ~80 m resolution, comprising a wide range of coastal uplift and subsidence rates. Coastal communities' policymakers and the general public can freely download the data (link in supplemental data).The four metropolitan areas majorly affected in these areas included San Francisco, Monterey Bay, Los Angeles, and San Diego."The vast majority of the San Francisco Bay perimeter is undergoing subsidence with rates reaching 5.9 mm/year," said Blackwell. "Notably, the San Francisco International Airport is subsiding with rates faster than 2.0 mm/year. The Monterey Bay Area, including the city of Santa Cruz, is rapidly sinking without any zones of uplift. Rates of subsidence for this area reach 8.7 mm/year. The Los Angeles area shows subsidence along small coastal zones, but most of the subsidence is occurring inland."Areas of land uplift included north of the San Francisco Bay Area (3 to 5 mm/year) and Central California (same rate).Going forward in the decades ahead, the coastal population is expected to grow to over 1 billion people by 2050, due to coastward migration. The future flood risk that these communities will face is mainly controlled by the rate of relative sea-level rise, namely, the combination of sea-level rise and vertical land motion. It is vital to include land subsidence into regional projections that are used to identify areas of potential flooding for the urbanized coast.Beyond the study, the ASU research team is hopeful that others in the scientific community can build on their results to measure and identify coastal hazards more broadly in the U.S. and around the world.
|
Geography
| 2,020 |
July 31, 2020
|
https://www.sciencedaily.com/releases/2020/07/200731102638.htm
|
Short wind turns with strong cooling effect
|
Sea surface temperatures in the tropics have a major influence on the climate in the tropics and the adjacent continents. For example, they determine the position of the Intertropical Convergence Zone and the beginning and strength of the West African monsoon. Therefore, it is important to understand the variability of sea surface temperatures for climate predictions. Until now, the seasonal cycle of sea surface temperature in the tropical North Atlantic could not be sufficiently explained. "More precisely, the sea surface is colder than predicted by the combination of previous direct observations of solar radiation, currents and mixing, especially in the summer months from July to September," explains Dr. Rebecca Hummels from the GEOMAR Helmholtz Centre for Ocean Research Kiel and first author of a study now published in
|
Ship-based observations with the German research vessel METEOR in September 2015 provided first measurements of a strong turbulent mixing event below the sea surface, where mixing was up to a factor of 100 higher than previously observed at this location. "When we noticed the greatly enhanced turbulence in the water column during data processing, we at first suspected a malfunction of our sensors," says Dr. Marcus Dengler, co-author of the study. "But when we also noticed strong currents at the ocean surface, we became curious." Precisely such events can explain the lower temperatures at the ocean surface."We were able to isolate the process behind this strong mixing event, which lasted only for a few days," explains Dr. Hummels. "It is a so-called inertial wave, which is a very short but intense flow event," Hummels continues. Inertial waves are horizontal wave phenomena in which the current at the surface rotates clockwise with time, whereas the movement rapidly decays with increasing depth. The different velocities at the surface and in the layer below cause instabilities and ultimately mixing between the warm water in the surface layer and the colder water below. Such inertial waves can be caused by brief variations in the near-surface winds. Up to now, generally only weak currents have been observed in this region and the rather steady trade winds at this time of year did not suggest particularly strong mixing events. However, wind variations are crucial to trigger these waves in the upper ocean. The winds do not have to be particularly strong, but ideally should rotate the same way the ocean currents do. Since such wind fluctuations are relatively rare and only last a few days, it has not yet been possible to measure such a strong wave phenomenon with the associated strong mixing in this region.After the discovery of this event during the METEOR cruise in September 2015, the Kiel scientists wanted to know more about the frequency and the actual impact of such events. "Through model-based data analysis, we were able to give a context to the in-situ observations," explains co-author Dr. Willi Rath from the Research Unit Ocean Dynamics at GEOMAR. "Together, we have scanned 20 years of global wind observations looking for similar events triggered by wind fluctuations and described their occurrence in the region and during the course of the year," Dr. Rath adds. This has supported the hypothesis that the temporal and spatial distribution of such events can indeed explain the gap in the heat balance of the upper ocean.The strong turbulent mixing caused by the inertial waves at the base of the surface layer is also crucial for biology: For example, the cold water that is mixed into the surface layer during such an event also brings nutrients from deeper layers into the upper ocean penetrated by sunlight. "This also explains the hitherto largely unexplained occurrence of chlorophyll blooms in this region, which could now also be attributed to the seasonally increased occurrence of these inertial waves," explains Dr. Florian Schütte, also co-author of the study.The ship measurements in the tropical Atlantic were carried out in close cooperation with the international PIRATA program. For more than 20 years, the PIRATA surface buoys have been providing valuable data for studies of ocean-atmosphere interaction, which were also used for this study. "Indeed, the intensive mixing measurements resulted from a failure in the hydraulic system of the METEOR, which made other measurements impossible at that time," says Prof. Dr. Peter Brandt, chief scientist of the expedition. Despite buoys and series of ship expeditions to this region, new phenomena are still being discovered -- sometimes by chance -- which decisively advance our understanding of the tropical climate.
|
Geography
| 2,020 |
July 30, 2020
|
https://www.sciencedaily.com/releases/2020/07/200730123658.htm
|
New method lets scientists peer deeper into ocean
|
Researchers have advanced a new way to see into the ocean's depths, establishing an approach to detect algae and measure key properties using light. A paper published in
|
"Traditional satellite remote sensing approaches can collect a wide range of information about the upper ocean, but satellites typically can't 'see' deeper than the top five or 10 meters of the sea," said Barney Balch, a senior research scientist at Bigelow Laboratory for Ocean Sciences and an author of the paper. "Harnessing a tool that lets us look so much deeper into the ocean is like having a new set of eyes."Lidar uses light emitted by lasers to gain information about particles in seawater, much as animals like bats and dolphins use sound to echolocate targets. By sending out pulses of light and timing how long it takes the beams to hit something and bounce back, lidar senses reflective particles like algae in the water.Lead study author Brian Collister used a shipboard lidar system to detect algae and learn about conditions deeper in the ocean than satellites can measure. The research team on this 2018 cruise was composed of scientists from Old Dominion University and Bigelow Laboratory for Ocean Sciences."The lidar approach has the potential to fill some important gaps in our ability to measure ocean biology from space," said Collister, a PhD student at Old Dominion University. "This technique will shed new light on the distribution of biology in the upper oceans, and allow us to better understand their role in Earth's climate."In the Gulf of Maine, the team used lidar to detect and measure particles of the mineral calcium carbonate, gathering information about a bloom of coccolithophores. These algae surround themselves with calcium carbonate plates, which are white in color and highly reflective. The plates scatter light in a unique way, fundamentally changing how the light waves are oriented -- and creating an identifiable signature that the lidar system can recognize.Balch's research team has studied the Gulf of Maine for over two decades through the Gulf of Maine North Atlantic Time Series. Their experience in finding and identifying algae in this ecosystem provided key background information for testing the lidar system in what turned out to be the largest coccolithophore bloom observed in the region in 30 years."This cruise allowed us an ideal opportunity to try the lidar system out with the ability to sample the water and know exactly what species were in it," Balch said. "Lidar has been used in the ocean for decades, but few, if any, studies have been done inside a confirmed coccolithophore bloom, which profoundly changes how light behaves in the environment."Coccolithophores thrive around the global ocean and exert a huge level of control on the biogeochemical cycles that shape the planet. Studying them is key to understanding global ocean dynamics, but field research is always costly. The team established that using lidar could potentially allow researchers to remotely estimate coccolithophore populations without stopping the ship to collect water samples -- increasing their ability to collect valuable data, thus also conserving precious ship-time funds.The research team also tested this approach in ocean environments that included the clear depths of the Sargasso Sea and the turbid waters off the coast of New York City. They found it to be effective across these diverse environments. Lidar systems can probe the ocean up to three times deeper than passive satellite remote sensing techniques that rely on the sun. Further research may establish approaches that allow lidar measurements to be taken by satellites, as well."It's a huge deal that we are learning to reliably identify particles in the ocean from a lidar system positioned above the water," said Richard Zimmerman, a study author and professor at Old Dominion University. "This is a significant advance, and it could revolutionize our ability to characterize and model marine ecosystems."This work was supported by the National Aeronautics and Space Administration, the National Science Foundation, and the Virginia SpaceGrant Consortium.
|
Geography
| 2,020 |
July 30, 2020
|
https://www.sciencedaily.com/releases/2020/07/200730123639.htm
|
Analyzing marine ecosystems from 6,000 to 5,000 years ago to anticipate changes caused by global warming
|
Global warming will modify the distribution and abundance of fish worldwide, with effects on the structure and dynamics of food networks. However, making precise predictions on the consequences of this global phenomenon is hard without having a wide historical perspective.
|
A study carried out at the University of Barcelona and the Southern Centre for Scientific Research (CADIC-CONICET, Argentina), analysed the potential implications in the distribution of the Argentinian hake (The study, published in the journal Researchers focused on the Atlantic coast of Isla Grande in Tierra del Fuego, in the extreme south of Argentina, where the hake is a key species for industrial fisheries. They collected samples from two archaeological sites dating from the Middle Holocene, that is, between 6,000 and 500 years ago, a period when temperatures would be analogous to those we are heading to in the future -according to climate models. "Remains from fish that lived in the warmest periods of the Holocene are specially interesting since they offer a plausible view of the future in the context of global warming. At the moment, the average annual temperature of the sea surface in Tierra del Fuego is about 7ºC, but during the Middle Holocene it reached 11 and 12ºC. Therefore, data on the biology of the hake during this period can provide information on the distribution of this species in a near future," note the authors.The presence of remains from other models of hake in the archaeological site Río Chico 1, in the north of Tierra del Fuego (Argentina), show the existence of a large population of hake in the northern east of Tierra del Fuego during the Middle Holocene. Since then, this population disappeared due to the cooling temperatures and their habitat was unknown.In order to discover the habitat of these fish, the first step in the study was to identify the remains through the mitochondrial DNA analysis and make a reconstruction of the size of old models. Then, researchers used the technique of carbon and nitrogen stable isotope analysis to study changes in the trophic position and the use of the habitat over time. This technique enables researchers to get information on the food intake, and the environment of the species that lived in a recent past, since the information is registered in the bone isotopic signal.Results show that Argentinian hake that lived in the Atlantic coast of Tierra del Fuego during the Middle Holocene had a broader isotopic niche and fed in more coastal habitats compared to those in current times. "This information, combined with strong winds and currents of the region, together with the lack of sailing technology during the Middle Holocene suggest that groups of aboriginal hunter-fisher-gatherers were likely to fish in the shore," note the authors. If the environmental conditions of a warmer world coincide with what prevails in the Middle Holocene, the Argentinian hake could be more abundant in the continental Argentinian platform of Tierra del Fuego. "From a fishing perspective, this situation suggests a potential increase of resources in shallow waters regarding Tierra del Fuego with important changes in the fishing industry in this region," highlights Lluís Cardona.According to the researchers, this methodology can be used with other species and in other areas of the planet. "In the future, we would like to know the changes that have taken place in the distribution and ecological niche of the hake and the cod in European waters," concludes the researcher.
|
Geography
| 2,020 |
July 30, 2020
|
https://www.sciencedaily.com/releases/2020/07/200730113055.htm
|
Extensive gas leaks in the North Sea: Abandoned wells
|
During expeditions to oil and gas reservoirs in the central North Sea in 2012 and 2013, scientists of the GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany) became aware of a phenomenon that had been hardly recognized before. They discovered that methane bubbles emerged from the seabed around abandoned wells. The gas originates from shallow gas pockets, which lie less than 1000 meters deep below the seafloor and that were not the target of the original drilling operations. An initial assessment showed that these emissions could be the dominant source of methane in the North Sea.
|
A new study published by GEOMAR scientists today in the During expeditions with RV POSEIDON in 2017 and 2019, the researchers were able to detect gas leakage at 28 of 43 directly investigated wells. 'The propensity for such leaks increases the closer the boreholes are located with respect to shallow gas pockets, which are normally uninteresting for commercial use. Apparently, however, the disturbance of the overburden sediment by drilling process causes the gas to rise along the borehole,' explains Dr. Matthias Haeckel from GEOMAR, who lead the study.In addition, the team used available seismic data of the industry from the British sector of the North Sea to make further statements about the boreholes in the area. 'We cover 20,000 square kilometres of seafloor in our study, which is approximately the size of Wales. This area contains 1,792 wells of which we have information. We evaluated a number of factors, such as location, distance to shallow gas pockets, and age, based on our direct measurements and weighted how these factors promote methane gas leakage from old wells. The most important factor was indeed the distance of the wells from the gas pockets,' explains Dr. Böttner.The positions of the boreholes and the location and extent of the gas pockets indicate that this area of the North Sea alone has the potential to emit 900 to 3700 tonnes of methane every year. 'However, more than 15,000 boreholes have been drilled in the entire North Sea,' adds Dr Haeckel.In seawater, methane is usually consumed by microbes. This can lead to local seawater acidification. In the North Sea, about half of the boreholes are at such shallow water depths that part of the emitted methane can escape into the atmosphere. Methane is the second most important greenhouse gas after carbon dioxide.The authors of the study encourage the industry to publish their data and recommend more independent emission measurements from abandoned wells in order to develop stricter guidelines and legally binding regulations for abandonment procedures.'The sources and sinks of methane, the second most important greenhouse gas after carbon dioxide, are still subject to large uncertainties. This also applies to emissions from the fossil energy sector. In order to better understand the reasons for the continuously increasing methane concentrations in the atmosphere and to be able to take mitigation measures, it is important to have a reliable numbers of the individual anthropogenic contributions,' summarizes Dr. Haeckel.
|
Geography
| 2,020 |
July 30, 2020
|
https://www.sciencedaily.com/releases/2020/07/200730092607.htm
|
Increasing Arctic freshwater is driven by climate change
|
New, first-of-its-kind research from the University of Colorado Boulder shows that climate change is driving increasing amounts of freshwater in the Arctic Ocean. Within the next few decades, this will lead to increased freshwater moving into the North Atlantic Ocean, which could disrupt ocean currents and affect temperatures in northern Europe.
|
The paper, published July 27, 2020 in "We hear a lot about changes in the Arctic with respect to temperature, how ecosystems and animals are going to be affected," said Rory Laiho, co-author and PhD student in atmospheric and oceanic sciences. "But this particular study gives an added perspective on what's happening physically to the ocean itself, which then can have important implications for ocean circulation and climate."Since the 1990s, the Arctic Ocean has seen a 10% increase in its freshwater. That's 2,400 cubic miles (10,000 cubic kilometers), the same amount it would take to cover the entire U.S. with 3 feet of water.The salinity in the ocean isn't the same everywhere, and the Arctic Ocean's surface waters are already some of the freshest in the world due to large amounts of river runoff.This freshwater is what makes sea ice possible: it keeps cold water at the surface, instead of allowing this denser liquid to sink below less dense, warm water. In this way, the Arctic Ocean is much different than other oceans. But as more freshwater exits the Arctic, this same stabilizing mechanism could disrupt the ocean currents in the North Atlantic that moderate winter temperatures in Europe.Such disruptions have happened before, during the "great salinity anomalies" of the 1970s and 80s. But these were temporary events. If too much cold freshwater from the Arctic continuously flows into the North Atlantic, the ocean turnover could be disrupted more permanently.Ironically, this would mitigate the impacts of global warming during winter in northern Europe for a while. But disrupting the ocean currents could have negative effects for climate long-term and on the North Atlantic's ecosystems.The main mission of the research for Alexandra Jahn, lead author of the new study and assistant professor in the Department of Atmospheric and Oceanic Sciences and the Institute of Arctic and Alpine Research, and her graduate student, Laiho, was to differentiate between natural variability cycles in Arctic freshwater amounts and climate change's impact. They examined the results from an ensemble of models run from 1920 to 2100."When we look at all the simulations together, we can see if they all do the same thing. If so, then that's due to a forced response," said Jahn. "If those changes are big enough so they could not occur without increasing greenhouse gases in the model simulations, that's what we call the emergence of a clear climate change signal. And here we see such clear climate change signals for the Arctic freshwater during the current decade."Their results showed that Nares Strait, which runs between Greenland and Canada and is the most northern gateway between the Arctic and more southern oceans -- will be the first place to see a freshwater export increase attributable to climate change in the next decade. Other straits farther south and east, including Davis and Fram straits, will be next to show this signal.The researchers also ran the models through different emissions scenarios to see if these changes will be affected by humans' emissions choices in the next few decades. They looked at the "business as usual" (over 4 degrees Celsius warming by the end of the century) scenario and what would happen if humans limited warming to 2 degrees Celsius, the upper end of IPCC (Intergovernmental Panel on Climate Change) targets for this century.They found that the change in freshwater in the Arctic Ocean and the amounts moving through the northern straits were unaffected since they will be subject to an increase in freshwater before the 2040s -- and the decisions made globally in the next few decades will not influence them, as these climatic changes are already in motion. But in the second half of this century, the two scenarios diverged, and increases in freshwater amounts were seen in more places in the high-warming scenario than in the low-warming scenario."What this work is showing us is that we're probably already experiencing the first of these changes, we just can't tell from the direct observations yet," Jahn said.All water from the Arctic Ocean eventually ends up in the North Atlantic. But timing is everything. Being able to predict the timing of the emergence of climate change signals will allow scientists to monitor upcoming changes in real time, and better understand how changes in the Arctic Ocean can impact climate worldwide."It fills a gap in our current understanding, and helps us ask new questions about what physically is happening in the Arctic," said Jahn.
|
Geography
| 2,020 |
July 29, 2020
|
https://www.sciencedaily.com/releases/2020/07/200729204748.htm
|
New current that transports water to major 'waterfall' discovered in deep ocean
|
An international team discovered a previously unrecognized ocean current that transports water to one of the world's largest "waterfalls" in the North Atlantic Ocean: the Faroe Bank Channel Overflow into the deep North Atlantic. While investigating the pathways that water takes to feed this major waterfall, the research team identified a surprising path of the cold and dense water flowing at depth, which led to the discovery of this new ocean current.
|
"This new ocean current and the path it takes toward the Faroe Bank Channel are exciting findings," said Léon Chafik, the lead author of the paper published in "The two discoveries reported here, in one of the best studied areas of the world ocean, is a stark reminder that we still have much to learn about the Nordic Seas," said co-author Thomas Rossby, emeritus professor at the URI Graduate School of Oceanography. "This is crucial given the absolutely fundamental role they play in the major glacial-interglacial climate swings."Previous studies dealing with this deep flow have long assumed that these cold waters, which flow along the northern slope of the Faroes, turn directly into the Faroe-Shetland Channel (the region the water flows through before reaching the Faroe Bank Channel). Instead, Chafik and the paper's co-authors show that there exists another path into the Faroe-Shetland Channel. They show that water can take a longer path all the way to the continental margin outside Norway before turning south heading toward this major waterfall. "Revealing this newly identified path from available observations was not a straightforward process and took us a good deal of time to piece together" said Chafik.The researchers also found this new path depends on prevailing wind conditions. "It seems that the atmospheric circulation plays a major role in orchestrating the identified flow regimes," added Chafik.The study further reveals that much of the water that will end up in the Faroe Bank Channel is not in fact transported along the western side of the Faroe-Shetland Channel (the region the water flows through before reaching the Faroe Bank Channel), as previously thought. Instead, most of this water comes from the eastern side of the Faroe-Shetland Channel where it is transported by a jet-like and deep-reaching ocean current. "This was a curious but very exciting finding, especially since we are aware that a very similar flow structure exists in the Denmark Strait. We are pleased that we were able to identify this new ocean current both in observations and a high-resolution ocean general circulation model," said Chafik."Because this newly discovered flow path and ocean current play an important part in the ocean circulation at higher latitudes, its discovery adds to our limited understanding of the overturning circulation in the Atlantic Ocean," said Chafik. "This discovery would not have been possible without many institutional efforts over the years."
|
Geography
| 2,020 |
July 29, 2020
|
https://www.sciencedaily.com/releases/2020/07/200729124359.htm
|
Alaskan seismometers record the northern lights
|
Aaron Lojewski, who leads aurora sightseeing tours in Alaska, was lucky enough to photograph a "eruption" of brilliant pink light in the night skies one night in February.
|
The same perturbations of the Earth's magnetic field that lit up the sky for Lojewski's camera were also captured by seismometers on the ground, a team of researchers reports in the journal By comparing data collected by all-sky cameras, magnetometers, and seismometers during three aurora events in 2019, University of Alaska Fairbanks seismologist Carl Tape and colleagues show that it's possible to match the striking display of lights with seismic signals, to observe the same phenomenon in different ways.Researchers have known for a while that seismometers are sensitive to magnetic fluctuations -- and have worked hard to find ways to shield their instruments against magnetic influence or to remove these unwanted signals from their seismic data. But the aurora study offers an example of how seismometers could be paired with other instruments to study these fluctuations."It can be hard to be definitive that these seismometer recordings are originating from the same influence as what's going on 120 kilometers up in the sky," Tape said. "It helps to have a simultaneous view of the sky, to given you more confidence about what you're seeing from the signals at ground level."The aurora borealis, or northern lights, occurs when solar winds -- plasma ejected from the Sun's surface -- meet the protective magnetic field that surrounds the Earth. The collision of particles produces colorful lights in the sky and creates fluctuations in the magnetic field that are sometimes called solar or space "storms." Magnetometers deployed on the Earth's surface are the primary instrument used to detect these fluctuations, which can significantly impact electrical grids, GPS systems and other crucial infrastructure. The aurora is commonly visible in wintertime in high-latitude regions such as Alaska.The seismometers in the study are part of the USArray Transportable Array, a network of temporary seismometers placed across North America as part of the EarthScope project. The array in Alaska and western Canada was completed in the fall of 2017. The aurora paper is one of several included in an upcoming SRL focus section about EarthScope in Alaska and Canada.These temporary seismic stations are not shielded from magnetic fields, unlike more permanent stations that are often cloaked in mu-metal, a nickel-iron alloy that directs magnetic fields around the instrument's sensors. As a result, "I was blown away by how well you can record magnetic storms across the array," said U.S. Geological Survey seismologist Adam Ringler, a co-author on the SRL paper.Last month, Ringler and his colleagues published a paper demonstrating how the array's 200-plus seismometers in Alaska can be used to record space weather, potentially augmenting the 13 magnetometers in operation in the state.Along with the all-sky camera data, seismic array data can help make sense of the strong variations in the magnetic field that occur in a magnetic east-west direction, adding a second dimension to typical north-south directional studies of the aurora and other magnetic storms, Tape and colleagues suggest.The researchers noted in their paper that the link between the aurora borealis and magnetic perturbations was first discovered in Sweden in 1741, and that a seismometer in Germany detected an atmosphere-generated magnetic event for the first time during a strong solar storm in 1994."People have been making these connections for 250 years," Tape said. "This shows that we can still make discoveries, in this case with seismometers, to understand the aurora."
|
Geography
| 2,020 |
July 29, 2020
|
https://www.sciencedaily.com/releases/2020/07/200729114844.htm
|
Melting Arctic sea ice during the summer of 2018
|
As sea ice in the Arctic retreats further and melts faster every decade, scientists are racing to understand the vulnerabilities of one of the world's most remote and unforgiving places. A study appearing July 29 in the journal
|
At the peak of its melting season, in July 2018, the Arctic was losing sea ice at a rate of 105,500 square kilometers per day -- an area bigger than Iceland or the state of Kentucky. "On the ground, I am sure it would have looked like an excellent summer month in the Arctic, in general, but over the past four decades, September sea-ice loss has accelerated to a rate of 12.8% per decade and 82,300 square kilometers per year," says co-author Avinash Kumar, a senior scientist at the National Centre for Polar and Ocean Research (NCPOR) in India.The researchers followed the warm water currents of the Atlantic north to the Arctic Ocean and tracked the ice as it subsequently retreated through the Chukchi, East Siberian, Laptev, Kara, and Barents seas. Thanks to higher temporal resolution and greater satellite coverage than had previously been available, they could also measure the ice's decline through variables such as its thickness, concentration, and volume in addition to its extent throughout the Arctic. This dramatic loss of sea ice culminated at the end of the boreal summer, when in September, the ice had been reduced to a mere third of its winter extent.Then, the team compared the decline to the previous four decades of data. "In the summer of 2018, the loss of sea ice was three times higher than the reported loss at the beginning of the satellite era," says Kumar. "Our study shows that both the minimum sea-ice extent and the warmest September records occurred in the last twelve years.""Every year, news pops up of a new record of high temperature or fastest loss of sea ice in the Arctic region, but in the global system, each portion of the planet receiving climate feedback will lead to changes in the other parts as well," Kumar says. "If the sea-ice decline continues at this pace, it can have a catastrophic impact by raising air temperatures and slowing down global ocean circulation." These global impacts are partly why he became interested in trying to decipher the mysteries of the polar regions as a doctoral student studying the coastal zone in India. Now, he works at NCPOR, whose scientific programs, he says, are "truly trans-hemispheric, cutting across from north to south."The researchers also turned their attention to the atmosphere, where they were able to gain insight into the processes that contribute to the loss of Arctic sea ice. They found not only that September of 2018 was the third warmest on record, but that there was a temperature difference within the Arctic itself: the temperature of the air above the Arctic Ocean (~3.5°C) was slightly higher than that of the Arctic land (~2.8°C).Their findings provide further evidence that ocean warming around the globe has influenced the natural cycle of the wind and pressure patterns in the Arctic. El Niños, or warm phases in long-term temperature cycles stemming from tropical regions, have long been known to drive extreme weather events around the world and are occurring with greater frequency as the world warms. El Niño cycles in the equatorial Pacific Ocean can carry warm air and water from tropical circulations to the Arctic, spurring the sea ice to melt. As the ice retreats, it cascades the Arctic into a positive feedback loop known as Arctic amplification, whereby the reduced ice extent gives way to darker ocean waters that absorb more of the sun's radiation. As it retains more heat, temperatures rise and more ice melts, causing the Arctic region to heat up faster -- about four times so -- than the rest of the world."If the decline of sea ice continues to accelerate at a rate of 13% per decade in September, the Arctic is likely to be free of ice within the next three decades," Kumar says. And just as sea-ice retreat is largely the result of anthropogenic pressures from across the globe, its impacts will be felt worldwide: this work adds to the mounting body of evidence that changes in the Arctic sea ice could be detrimental to weather patterns spanning the globe. He says, "The changes taking place in the Arctic can lead to other changes in lower latitudes, such as extreme weather conditions. The world should be watching tropical countries like India, with our research center saddled close to the beaches of Goa, and trying to understand -- even in a small way -- more about climate change and the polar regions."This work was supported by the National Centre for Polar and Ocean Research, Goa, the Ministry of Earth Science, New Delhi, and the University Grants Commission, New Delhi.
|
Geography
| 2,020 |
July 29, 2020
|
https://www.sciencedaily.com/releases/2020/07/200729114838.htm
|
Newer PFAS contaminant detected for first time in Arctic seawater
|
Per- and polyfluoroalkyl substances (PFAS), found in many household products and food packages, have raised concerns because of their persistence and possible toxicity to people and wildlife. Because the compounds don't break down naturally, they have become environmental contaminants. Now, researchers reporting in ACS'
|
After studies indicated that two PFAS -- PFOA and PFOS -- can cause cancer, a compromised immune response and other health problems in lab animals, the two compounds were voluntarily phased out by industry. However, these legacy compounds are still widely detected in the environment. Intended as a safer replacement for PFOA, HFPO-DA (sold under the trade name GenX) is now thought to pose similar health and persistence concerns. Hanna Joerss and colleagues wanted to investigate the long-range, oceanic transport of legacy and replacement PFAS to the Arctic Ocean -- a remote body of water connected to the Atlantic Ocean by the Fram Strait, which is located between Svalbard and Greenland.Aboard an icebreaker research ship, the team collected water samples along two Fram Strait currents entering and exiting the Arctic Ocean and along a path from Europe's North Sea to the Arctic Ocean. Using mass spectrometry, the researchers detected 11 PFAS in the ocean water, including PFOA, HFPO-DA and other long- and short-chain PFAS. This was the first time that HFPO-DA had been detected in seawater from a remote region, indicating that the compound can be transported long distances. Higher levels of PFAS were detected in the water exiting the Arctic Ocean compared with the water entering the Arctic from the North Atlantic. The PFAS composition in the outgoing water suggested that more of these compounds arose from atmospheric sources than from ocean circulation.
|
Geography
| 2,020 |
July 29, 2020
|
https://www.sciencedaily.com/releases/2020/07/200729114828.htm
|
Indigenous people vital for understanding environmental change
|
Grassroots knowledge from Indigenous people can help to map and monitor ecological changes and improve scientific studies, according to Rutgers-led research.
|
The study, published in the "Scientists and Indigenous communities working together are needed to understand our rapidly changing world," said lead author Pamela McElwee, an associate professor in the Department of Human Ecology in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. "Many Indigenous peoples have unique abilities to notice ecosystems altering before their eyes by using local indicators, like the color of fat in hunted prey or changes in types of species found together. Scientists wouldn't be able to perform these kinds of observations over the long run for many reasons, including costs and the remoteness of some areas. So Indigenous knowledge is absolutely essential for understanding the cumulative impacts of biodiversity loss and ecosystem degradation."Indigenous and local knowledge is the practical information that people use to manage resources and pass on between generations. Such knowledge benefits conservation initiatives and economies that depend on natural resources in vast areas of the world.The study follows the Global Assessment Report on Biodiversity and Ecosystem Services released last year by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. That report was the first global ecological assessment to use Indigenous and local knowledge as a source of evidence.The new study, by researchers at many institutions who were part of the global assessment, provides background on how the report tapped into Indigenous knowledge systems and lessons learned. Working with these local sources of information in ecological research and in management requires a deliberate approach from the start, additional resources and engagement with stakeholders reflecting diverse worldviews, McElwee said."Partnering with Indigenous peoples can help scientists and researchers understand how natural and cultural systems affect each other, identify trends through diverse indicators and improve sustainable development goals and policies for all," she said.
|
Geography
| 2,020 |
July 29, 2020
|
https://www.sciencedaily.com/releases/2020/07/200729114743.htm
|
Amazonian Indigenous territories are crucial for conservation
|
A new study shows that Indigenous territories represent around 45% of all the remaining wilderness areas in the Amazon, comprising an area of three times the surface of Germany. At a time when the Amazon forests face unprecedented pressures, overcoming divergences and aligning the goals of wilderness defenders and Indigenous peoples is paramount to avoid further environmental degradation.
|
"In this paper we show that supporting Indigenous peoples' rights is in the interest of the conservation agenda," explains Dr. Álvaro Fernández-Llamazares, the first author of the study, from the University of Helsinki. "The future of a substantial proportion of the Amazon's biodiversity depends largely on coordinated action to support and strengthen Indigenous peoples' rights across the entire region."The authors argue that the convergence of the agendas and priorities of both wilderness-centred conservationists and Indigenous peoples is more important than ever, as some of the government in the region have started to trample over commitments towards globally agreed goals on both the environment and Indigenous peoples' rights."There is no doubt that the Amazon is at a crossroads in its social-ecological history," adds Dr. Fernández-Llamazares. "Rollbacks on environmental protections and Indigenous Peoples rights across the entire region are opening up vast natural areas to new external pressures."All these macroeconomic and political forces are being felt in both wilderness areas and Indigenous Peoples territories. However, disputes on whether conserving wilderness should come at the expense of Indigenous peoples rights undermine potential for collaborative conservation.The study underscored the substantial role of Indigenous territories in buffering against deforestation through advanced geospatial analyses based on available satellite data. These lands account for less than 15% of all the forest loss occurring within the Amazon's last wilderness frontiers. This is largely evidenced throughout the southern rim of the Amazon, where Indigenous territories represent the only islands of biological and cultural diversity in the larger landscape."The concept of wilderness has a contentious history across much of the Global South, as it is based on the assumption that humans have inherently negative impacts on nature," highlights Prof. Eduardo S. Brondizio, a researcher from Indiana University Bloomington and senior author of the study."Yet, the Amazon is a classic example of how long-term interactions between Indigenous peoples and forests can be linked to positive environmental outcomes. We have known for decades that a significant portion of the region's supposedly pristine forests are in fact cultural forests,"he notes. "Indigenous peoples, and also other traditional communities, show that it is possible to successfully combine forest conservation, management and agroforestry systems."In view of this, the authors call for a more socially inclusive notion of wilderness in order to align the agendas and priorities of both wilderness-focused conservationists and Indigenous peoples against a new wave of frontier expansion.
|
Geography
| 2,020 |
July 28, 2020
|
https://www.sciencedaily.com/releases/2020/07/200728113533.htm
|
Deep sea microbes dormant for 100 million years are hungry and ready to multiply
|
For decades, scientists have gathered ancient sediment samples from below the seafloor to better understand past climates, plate tectonics and the deep marine ecosystem. In a new study published in
|
The research team behind the new study, from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the URI Graduate School of Oceanography, the National Institute of Advanced Industrial Science and Technology, the Kochi University and Marine Works Japan, gathered the ancient sediment samples ten years ago during an expedition to the South Pacific Gyre, the part of the ocean with the lowest productivity and fewest nutrients available to fuel the marine food web."Our main question was whether life could exist in such a nutrient-limited environment or if this was a lifeless zone," said the paper's lead author Yuki Morono, senior scientist at JAMSTEC. "And we wanted to know how long the microbes could sustain their life in a near-absence of food."On the seafloor, there are layers of sediment consisting of marine snow (organic debris continually sourced from the sea surface), dust, and particles carried by the wind and ocean currents. Small life forms such as microbes become trapped in this sediment.Aboard the research drillship With fine-tuned laboratory procedures, the scientists, led by Morono, incubated the samples to coax their microbes to grow. The results demonstrated that rather than being fossilized remains of life, the microbes in the sediment had survived, and were capable of growing and dividing."We knew that there was life in deep sediment near the continents where there's a lot of buried organic matter," said URI Graduate School of Oceanography professor and co-author of the study Steven D'Hondt. "But what we found was that life extends in the deep ocean from the seafloor all the way to the underlying rocky basement."Morono was initially taken aback by the results. "At first I was skeptical, but we found that up to 99.1% of the microbes in sediment deposited 101.5 million years ago were still alive and were ready to eat," he said.With the newly developed ability to grow, manipulate and characterize ancient microorganisms, the research team is looking forward to applying a similar approach to other questions about the geological past. According to Morono, life for microbes in the subseafloor is very slow compared to life above it, and so the evolutionary speed of these microbes will be slower. "We want to understand how or if these ancient microbes evolved," he said. "This study shows that the subseafloor is an excellent location to explore the limits of life on Earth."Before looking ahead to future research, D'Hondt took time to reflect on Morono's achievement. "What's most exciting about this study is that it shows that there are no limits to life in the old sediment of the world's ocean," said D'Hondt. "In the oldest sediment we've drilled, with the least amount of food, there are still living organisms, and they can wake up, grow and multiply."
|
Geography
| 2,020 |
July 27, 2020
|
https://www.sciencedaily.com/releases/2020/07/200727154216.htm
|
Pristine environments offer a window to our cloudy past
|
A new study uses satellite data over the Southern Hemisphere to understand global cloud composition during the industrial revolution. This research tackles one of the largest uncertainties in today's climate models -- the long-term effect of tiny atmospheric particles on climate change.
|
Climate models currently include the global warming effect of greenhouse gases as well as the cooling effects of atmospheric aerosols. The tiny particles that make up these aerosols are produced by human-made sources such as emissions from cars and industry, as well as natural sources such as phytoplankton and sea spray.They can directly influence the flow of sunlight and heat within the Earth's atmosphere as well as interact with clouds. One of the ways that they do this is by bolstering clouds' ability to reflect sunlight back into space by increasing their droplet concentration. This in turn cools the planet. The amount of sunlight that is reflected to space is referred to Earth's albedo.However, there has been extremely limited understanding of how aerosol concentration has changed between early-industrial times and the present day. This lack of information restricts the ability of climate models to accurately estimate the long-term effects of aerosols on global temperatures -and how much of an effect they could have in the future.Now, an international study led by the Universities of Leeds and Washington has recognised that remote, pristine parts of the Southern Hemisphere provide a window into what the early-industrial atmosphere looked like.The team used satellite measurements of cloud droplet concentration in the atmosphere over the Northern Hemisphere -- heavily polluted with today's industrial aerosols -- and over the relatively pristine Southern Ocean.They used these measurements to quantify the possible changes due to industrial aerosols in Earth's albedo since 1850.The results, published today in the journal Co-lead author, Daniel McCoy, Research Fellow in the School of Earth and Environment at Leeds, said: "Limitations in our ability to measure aerosols in the early-industrial atmosphere have made it hard to reduce uncertainties in how much warming there will be in the 21st century."Ice cores provide carbon dioxide concentrations from millennia in the past, but aerosols don't hang around in the same way. One way that we can try to look back in time is to examine a part of the atmosphere that we haven't polluted yet."These remote areas allow us a glimpse into our past and this helps us understand the climate record and improve our predictions of what will happen in the future."Co-lead author, Isabel McCoy, from the Atmospheric Sciences Department at Washington, said: "One of the biggest surprises for us was how high the concentration of cloud droplets is in Southern Ocean clouds. The way that the cloud droplet concentration increases in summertime tells us that ocean biology is playing an important role in setting cloud brightness in unpolluted oceans now and in the past."We see high cloud droplet concentrations in satellite and aircraft observations, but not in climate models. This suggests that there are gaps in the model representation of aerosol-cloud interactions and aerosol production mechanisms in pristine environments."As we continue to observe pristine environments through satellite, aircraft, and ground platforms, we can improve the representation of the complex mechanisms controlling cloud brightness in climate models and increase the accuracy of our climate projections."Co-author Leighton Regayre, a Research Fellow also from the School of Earth and Environment at Leeds, said: "The science supporting our climate models is improving all the time. These models are tackling some of the most pressing and complex environmental questions of the modern era and climate scientists have always been up front about the fact that uncertainties exist."We are only going to reach the answers we need to combat global warming by regularly interrogating the science. Our team used millions of variants of a model to explore all the potential uncertainties, the equivalent of having a clinical trial with millions of participants."We hope our findings, along with studies on the detailed process of aerosol production and aerosol-cloud interactions in pristine environments that our work has motivated, will help guide the development of the next generation of climate models."
|
Geography
| 2,020 |
July 27, 2020
|
https://www.sciencedaily.com/releases/2020/07/200727145819.htm
|
Patterns in sediment linked to rain, uplift and sea level change
|
Forces that shape the Earth's surface are recorded in a number of natural records, from tree rings to cave formations.
|
In a recent study, researchers from The University of Texas at Austin show that another natural record -- sediments packed together at basin margins -- offers scientists a powerful tool for understanding the forces that shaped our planet over millions of years, with implications on present day understandingThe study was published in the journal "We are trying to find a way to distinguish the tectonics and the climate signals," said lead author Jinyu Zhang, a research associate at UT's Bureau of Economic Geology. "By using this numerical model we suddenly have this power to simulate the world under different tectonics and climate."Zoltán Sylvester and Jacob Covault, both research scientists at the bureau, co-authored the paper.Geoscientists have long looked to sedimentary basins for clues about Earth's past climate. That's because sediment supply is closely linked to environmental factors, such as rainfall or snowfall, that influence sediment creation through erosion and sediment transport across a landscape and into a basin. Tectonic factors also influence sediment creation, with increasing uplift associated with more sediment and decreasing uplift with less.However, despite knowledge of sediment supply being linked with climate and tectonics, the researchers said little is known about how changes in these phenomena directly influence how sediment is deposited along basin margins over long time scales.This study changes that, with Zhang using the open-source computer program pyBadlands to create a "source-to-sink" 3D model that tracks how changes in precipitation, tectonic uplift and sea level influence sediment erosion and deposition. The model uses topography inspired by the Himalaya Mountains and Indus River Delta to track the sediment as it makes its way from the mountains, through a river system, and settles into a basin margin over millions of years."This is one of the first [models] to put the landscape evolution part with the stratigraphic response, depositional response, and do it in 3D," Covault said. "Jinyu has made a really great step in putting this all together."The researchers ran 14 different scenarios -- each with a different climatic, tectonic, and sea level settings -- over a simulated time period of 30 million years to investigate changes in landscape topography and sediment deposition.The different scenarios created distinct patterns in sediment deposition, which allowed the researchers to draw general conclusions about how tectonic and climatic factors affect basin margin growth. For example, changes in uplift take millions of years to affect change in the basin margin sediments, but once those changes are in effect, they set a new baseline for behavior. In contrast, changes in precipitation cause much more abrupt change, followed by a return to the depositional behavior observed before the climate shift.The scenarios showed that sea level could potentially complicate the delivery of the signal of tectonic change into the basin. For example, an increase in sea level flooded coastal regions and interfered with sediment reaching a basin margin. But when this scenario was paired with increased precipitation, the sediment supply was large enough to make it to the basin margin.Gary Hampson, a professor at Imperial College London who was not part of the study, said that the model provides important guidelines for geoscientists looking to reconstruct Earth's past."The results increase the confidence with which geoscientists can interpret tectonic and climatic histories in the geologic archives of basin margins," he said.Zhang spent the past two years learning the programming language Python so he could use the pyBadlands software, which was developed by the University of Sydney's Tristan Salles.Sylvester, who leverages similar tools to study erosion and sedimentation in river systems, said that the computing tools available to geoscientists are making long-standing yet fundamental questions in geosciences more accessible than ever."It's an exciting time," he said. "It's increasingly easier to investigate the stratigraphic record in a quantitative way."
|
Geography
| 2,020 |
July 27, 2020
|
https://www.sciencedaily.com/releases/2020/07/200727125342.htm
|
Make your own greenhouse gas logger
|
Researchers at Linköping University's Department of Thematic Studies, Environmental Change, have developed a simple logger for greenhouse gas flows. It is built using inexpensive and easily available parts, and provides data on levels of methane, carbon dioxide, temperature and humidity.
|
"So far, measurement instruments have been so expensive that society's mapping of greenhouse gas emissions has had to rely on rough models. It's extremely important that we can make lots of proper measurements locally, so we can test whether measures for reducing emissions actually work. We hope that our simple and cost-efficient logger can contribute to more such measurements" says David Bastviken, professor at Environmental Change, and author of an article in A current limitation when it comes to determining the greenhouse gas fluxes has been the lack of reliable low-cost measurement methods that can be widely available in society. In 2015, David Bastviken and colleagues described and published a logger for carbon dioxide, which is now used for various types of environmental measurements. However for methane, more complicated and expensive measurement equipment has so far been required. In the current article in Methane, CH4, is one of the most important long-lived greenhouse gases which contributes greatly to global warming. Since the 1750s, its relative increase in the atmosphere has been greater than for other greenhouse gases. There are many different sources and examples including incomplete combustion, handling of natural gas and biogas, and microbial production in agriculture, wetlands and lakes. However the large number of sources that can vary greatly in ways not fully understood makes it difficult to quantify fluxes and to propose best practices for flux mitigation. In addition, the discovery that lakes, rivers and flooded forests are large sources of methane, made by David Bastviken and his colleagues as recently as 2011 and later, shows that major methane sources are still being discovered."We have now built and tested a simple logger based on the open-source Arduino hardware. The parts are available in many electronics stores; they can be ordered online and cost about 200 euro. We have also developed more precise ways to calibrate the methane sensor, to enable the measurement of greenhouse gas fluxes at a very low cost," says David Bastviken.The researchers hope that the logger will make it easier for all interested, and in e.g. education and environmental monitoring, to monitor greenhouse gas emissions."We also propose simplified but satisfactory ways to calibrate the sensors that don't require continuous access to advanced research laboratories. This can make measurements easier, for instance in developing countries," says David Bastviken.
|
Geography
| 2,020 |
July 23, 2020
|
https://www.sciencedaily.com/releases/2020/07/200723143637.htm
|
Coral reefs show resilience to rising temperatures
|
Rising ocean temperatures have devastated coral reefs all over the world, but a recent study in
|
"Our 44-year study shows that the amount of living coral has not changed in the ETP," said James W. Porter, the paper's senior author. "Live coral cover has gone up and down in response to El Niño-induced bleaching, but unlike reefs elsewhere in the Caribbean and Indo Pacific, reefs in the ETP almost always bounce back," he said.The study was conducted by an international team of researchers from across the region led by Dr. Mauricio Romero-Torres of the Pontificia Universidad Javeriana and Unidad Nacional para la Gestión del Riesgo de Desastres (the National Unit for Disaster Risk Management or UNGRD) in Bogotá, Colombia. The group examined coral cover data for the area, which stretches from Baja California to the Galapagos Islands, from 1970-2014. During that time there were several El Niño events -- periods when the equatorial Pacific Ocean reaches unusually high temperatures. Excessive heat can kill the symbiotic algae that inhabit the corals, leading to widespread coral bleaching and death.The researchers found that while losses of coral cover followed the worst of those episodes, in many cases ETP reefs recovered within 10-15 years."So much of my career has been spent documenting coral reef decline that to discover a large area of the tropics where coral reefs are holding their own is very gratifying," said Porter, professor emeritus in the University of Georgia Odum School of Ecology.They hypothesized that several key factors allowed the ETP reefs to bounce back.First, corals in this area are mostly pocilloporids, a type of coral that reproduces at high rates. They also contain species of symbiotic algae that are particularly tolerant to extreme temperatures.Patterns of weather and geography in the ETP may also play a role. Areas having heavier cloud cover or upwelling of cooler waters may survive locally and be able to reseed more severely affected reefs elsewhere.Another important factor may be "ecological memory," meaning that ETP corals may have become conditioned to heat stress over the years, through mechanisms such as genetic adaptation and epigenetic inheritance, whereby parents pass on these survival traits to their offspring."The key to survival for future reefs may not be an immunity to stress, but rather an ability to recover and regrow after stress," said Porter. "ETP reefs show us what this might look like."Porter said that the study is also important as an example of the need for maintaining long-term original data, which was crucial to the research."As soon as Dr. Romero contacted me, I consulted my original dive logs, made when I was a Smithsonian Pre-Doctoral Fellow in Panama in 1970," said Porter. "I realized immediately that my hand-written field notes contained everything needed to anchor this study with the oldest data (1970) used in this long-term survey. Particularly in a changing world, we need to archive and store original data carefully," he said. "Knowing what the world looked like in the past may be the best way to set restoration goals in the future.""This research teaches the relevance of doing science with FAIR standards (findable, accessible, interoperable and reusable) so that other researchers in the region can continue the work and estimate the effects of the next El Niño phenomenon on the ETP," said Romero.
|
Geography
| 2,020 |
July 23, 2020
|
https://www.sciencedaily.com/releases/2020/07/200723092749.htm
|
Lightning strikes more than 100 million times per year in the tropics
|
Researchers at the Smithsonian Tropical Research Institute (STRI) in Panama have published dramatic maps showing the locations of lightning strikes across the tropics in
|
"Lightning influences the ability of forests to store biomass, and therefore carbon, because it tends to strike the largest trees," said Evan Gora, a post-doctoral fellow at STRI who recently finished his doctorate at the University of Louisville. "And lightning strikes may also be very important in savanna ecosystems."Because lightning is so challenging to study, it has been overlooked as a change-agent in tropical forests where researchers focus their energy on more obvious disturbances like drought, fire, and high winds.In a previous study, the first to examine the effects of lightning on a tropical forest landscape, the same team found that lightning probably kills half of the biggest trees in a Panamanian forest. Tropical ecologist Steve Yanoviak, study coauthor and professor at the University of Louisville who was studying ants in the tropical forest canopy -- and often thought about the role of lightning while climbing trees, invited lightning researchers Jeffrey Burchfield and Phillip Bitzer from the University of Alabama at Huntsville to set up lightning detectors at STRI's Barro Colorado Island Research Station."We found that a lightning strike damages a total of 23.6 trees and kills 5.5 of these trees within a year, on average," Yanoviak said.Now the team is asking how lightning affects tropical ecosystems everywhere. Gora led the effort to map lightning strike counts based on images from the Earth Networks Global Lightning Network (ENGLN) onto a map of tropical ecosystems created using land-cover categories from the International Geosphere-Biosphere Program and the Moderate Resolution Spectroradiometer (MODIS) Land Cover Climate Modeling Grid.Based on satellite data about strike locations and on-the-ground effects around 92 lightning strikes, including many from the previous study, Gora and his colleagues estimated that lightning damages approximately 832 million tropical trees each year. Roughly a quarter of the trees probably die from their injuries.Gora and colleagues then asked whether there was a connection between the number of lightning strikes and the type of ecosystem, its biomass and climate variables like rainfall and temperature. They found that lightning strikes were more frequent in forests, savannas and urban areas than in grasslands, shrublands and croplands.Forests that experience more lightning strikes each year have fewer large trees per hectare, perhaps because the large individual trees in these forests stand out more, higher rates of woody biomass turnover (more tree biomass dies each year) and less total aboveground biomass.But more burning questions remain. No one knows why some trees survive lightning strikes while others die, although it is likely that trees have evolved ways of coping with such a common threat.And, as climate change accelerates, polluted, hot air over cities may also increase the number of lightning strikes there. What will the effects be on vegetation in urban areas?"This is the best evidence to date that lightning is a major disturbance influencing tropical forest dynamics and structure," said STRI staff scientist and study co-author Helene Muller-Landau, "We suspect that our study vastly underestimates the total effect of lightning. Lightning strikes may play a major role in forest biomass/carbon cycling not only in tropical forests but also in other tropical ecosystems."
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722163246.htm
|
Discovery of first active seep in Antarctica provides new understanding of methane cycle
|
The discovery of the first active methane seep in Antarctica is providing scientists new understanding of the methane cycle and the role methane found in this region may play in warming the planet.
|
A methane seep is a location where methane gas escapes from an underground reservoir and into the ocean. Methane seeps have been found throughout the world's oceans, but the one discovered in the Ross Sea was the first active seep found in Antarctica, said Andrew Thurber, a marine ecologist at Oregon State University."Methane is the second-most effective gas at warming our atmosphere and the Antarctic has vast reservoirs that are likely to open up as ice sheets retreat due to climate change," Thurber said. "This is a significant discovery that can help fill a large hole in our understanding of the methane cycle."The researchers' findings were published today in the journal Methane is a greenhouse gas that is 25 times more powerful than carbon dioxide at warming the planet. Most methane in the ocean water and sediment is kept out of the atmosphere by microbes that consume it.Thurber and his colleagues discovered that the microbes around the Antarctic seep are fundamentally different that those found elsewhere in the world's oceans. This helps researchers better understand methane cycles and the factors that determine whether methane will reach the atmosphere and contribute to further warming, Thurber said.The Ross Sea seep was discovered in an area that scientists have studied for more than 60 years, but the seep was not active until 2011, said Thurber, an assistant professor in Oregon State's College of Earth, Ocean, and Atmospheric Sciences and the College of Science's Department of Microbiology.An expansive microbial mat, about 70 meters long by a meter across, formed on the sea floor about 10 meters below the frozen ocean surface. These mats, which are produced by bacteria that exist in a symbiotic relationship with methane consumers, are a telltale indication of the presence of a seep, said Thurber."The microbial mat is the road sign that there's a methane seep here," Thurber said. "We don't know what caused these seeps to turn on. We needed some dumb luck to find an active one, and we got it."Thurber happened to be in Antarctica in 2012 when another researcher told him about a "microbial waterfall" and thought it was something he should look at. Thurber was able to confirm the seep's presence, collect samples and analyze the seep and its environment. When he returned to the site in 2016 to conduct further study, he also discovered a second seep nearby.Antarctica is believed to contain as much as 25 percent of Earth's marine methane. Having an active seep to study gives researchers new understanding of the methane cycle and how that process might differ in Antarctica compared to other places on the planet, Thurber said.For example, researchers have found that the most common type of microbe that consumes methane took five years to show up at the seep site and even then those microbes were not consuming all of the methane, Thurber said. That means some methane is being released and is likely working its way into the atmosphere.Studying the site over a five-year time span allowed researchers to see how microbes respond to the formation of a seep, said Seabrook, who earned her doctorate at OSU and is now a post-doctoral scholar at the National Institute of Water and Atmospheric Research in Wellington, New Zealand."What was really interesting and exciting was that the microbial community did not develop as we would have predicted based on other methane seeps we have studied around the globe," she said.Researchers had assumed that microbes should respond really quickly to changes in the environment, but that wasn't reflected in what OSU's team saw in Antarctica, Thurber said."To add to the mystery of the Antarctic seeps, the microbes we found were the ones we least expected to see at this location," he said. There may be a succession pattern for microbes, with certain groups arriving first and those that are most effective at eating methane arriving later."We've never had the opportunity to study a seep as its forming or one in Antarctica, because of this discovery we can now uncover whether seeps just function differently in Antarctica or whether it may take years for the microbial communities to become adapted," Thurber said."Animals in Antarctica are very different than elsewhere in the world as the continent has been separated from the rest of the globe for more than 30 million years -- a long time for evolution to act," he said. "That has resulted in a remarkable diversity of fauna that we only find there. That may also contribute to the differences in microbes there."It is important to understand how methane seeps behave in this environment so researchers can begin factoring those differences into climate change models, Thurber said. He hopes to return to the site to monitor its evolution and conduct further research.
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722163233.htm
|
2,000 years of storms in the Caribbean
|
The hurricanes in the Caribbean became more frequent and their force varied noticeably around the same time that classical Mayan culture in Central America suffered its final demise: We can gain these and other insights by looking at the climate archive created under the leadership of geoscientists from Goethe University and now presented in an article in "Nature" journal's
|
Tropical cyclones in the Atlantic (hurricanes) are a substantial threat for the lives and property of the local population in the Caribbean and neighboring regions, such as the south-east of the USA. The storms' increasing force, described in Chapter 15 of the report by the Intergovernmental Panel on Climate Change (IPCC Report), raises the probability of ecological and social catastrophes, as the occurrence of such cyclones over the past 20 years, which caused devastating damage, has shown. The climate models used to date, which could help to estimate the danger better, are, however, based on data that are lacking in spatial and temporal depth. Instrumental climate data, such as regular measurement of sea surface temperatures and reliable chronicling of hurricanes, date back only to the 19th century, at most.In the framework of a research project (Gi 222/31) funded by the German Research Foundation, the Biosedimentology Working Group at the Department of Geosciences of the Faculty of Geosciences and Geography (Professor Eberhard Gischler) of Goethe University has now been able to build up and analyze a sedimentary "storm archive" that covers almost the entire Common Era (2,000 years) with annual resolution. The archive comprises fine-grained annual layers of sediments from the 125-meter-deep bottom of the Blue Hole, a flooded karst sinkhole on the Lighthouse Reef Atoll off the coast of Belize (Central America). There, 2.5 mm of lime mud, composed of shell debris from organisms in the reef lagoon along with changing amounts of organic matter, collect year after year. Coarser layers up to several centimeters thick that constitute tempestites (storm sediments) are intercalated in these fine-grained sediments. They mostly consist of shell debris from reef organisms living on the edge of the atoll. The almost 9-metre-long drill core from the bottom of the Blue Hole, which was recovered with the help of an electrical vibracorer, spans the last 1,885 years with a total of 157 storm layers.In the framework of extensive studies conducted by doctoral researcher Dominik Schmitt and collaboration between the Biosedimentology Working Group and colleagues at the University of Bern (Switzerland), it has become apparent that both short-term and long-term climate phenomena, such as the El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO), have influenced storm activity over the last 2,000 years and are mirrored in the new climate archive. The beginning of the Medieval Warm Period (approx. AD 900-1100) constitutes an important transition period when the activity of tropical cyclones changed substantially, presumably in conjunction with the shift of the Intertropical Convergence Zone (the low-pressure zone where northern and southern trade winds converge) towards the south: From AD 100-900, storm activity in the region tended to be more stable and weaker, while since AD 900 up until today it has been more variable and more vigorous. Interestingly, this change in the increase of cyclone frequency goes hand in hand with the occurrence of a few, very thick, coarse-grained storm layers and coincides with the final demise of the classical Mayan culture in Central America. It is possible that the increased impact of hurricanes on the Central American mainland, combined with extensive flooding of cultivated land in the Mayan lowlands and rainfall-induced erosion in the backlands of the Mayan Mountains of Belize -- apart from the recurring periods of drought already known -- was another environmental factor that influenced the end of the Maya's high culture.
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722142739.htm
|
What happens in Vegas, may come from the Arctic?
|
A cave deep in the wilderness of central Nevada is a repository of evidence supporting the urgent need for the Southwestern U.S. to adopt targets aimed at reducing greenhouse gas emissions, a new UNLV study finds.
|
UNLV climate scientist Matthew Lachniet and colleagues have compiled a detailed, 13,000-year climate history from stalagmite specimens in Leviathan Cave, located in the southern Great Basin, which provides clues for the mitigation of climate change today.These ancient climate records show that Nevada was even hotter and drier in the past than it is today, and that one 4,000-year period in particular may represent a true, "worst-case" scenario picture for the Southwest and the Colorado River Basin -- and the millions of people who rely on its water supply.At that time, the long-term hot and dry climate of the region was linked to warm Arctic seas and a lack of sea ice, as well as warming in the western tropical Pacific Ocean, the cave record shows.This parallels today and the near future, as the release of human carbon emissions into the atmosphere will warm the Arctic and possibly the western tropical Pacific, and is expected to result in long-term arid conditions for Nevada and the broader Colorado River Basin.If the arid conditions become permanent, then the water supply in the Colorado River Basin is expected to decrease, which researchers say would imperil critical water resources for millions of people who live in the Southwest U.S."The last few decades have seen increasingly severe 'hot droughts' in the Colorado River Basin, when high temperatures coincide with less rainfall, and which have startled climate scientists and water policy managers," Lachniet said. "But these dry intervals don't usually last more than a few decades. In contrast, our new data show that Nevada climate can experience an extended interval of aridity for thousands of years, not just a few decades."The recent Southwestern U.S. drought that began in 2001, which has resulted in historic low reservoir levels in Lake Mead, is one indicator of the gravity of the problem. The Colorado River and Rio Grande basins are critical human support systems as their headwaters in the Rocky Mountains supply snow-fed water for myriad economic uses and support 56 million residents throughout the region."'Business as usual' scenarios for anthropogenic warming carry the risk of tipping the Southwest into an extended state of aridification," researchers wrote.The paper, published in the journal Stalagmites -- like those located in Leviathan Cave -- are common cave formations that act as ancient rain gauges to record historic climate data. Stalagmites grow upward at rates of inches every few hundred years as mineral-rich waters seep through the ground above and drop from the tips of stalactites on cave ceilings.These deposits more accurately represent a long-term shift toward a more arid climate as they hold data that extends deeper into the past.A former analysis of one tree ring record, for example, pointed to a 10-year drought in the Medieval era as being a "worst case" predictor of a future, comparable drought, as compared to the more persistent and sustained 4,000-year period of aridity presented in Lachniet's new study.Regionally, paleoclimate records from other sources like lakes, landforms, pollen, and others, also support the conclusion of warmth and aridity during the same 4,000-year period.Researchers also found that the Leviathan Cave region, where the stalagmite specimen was collected, is representative of climate conditions in most of the Mojave Desert and the southern Great Basin, and that the data has implications for the broader desert region.Lachniet and colleagues say that their study can be a resource for policymakers today in adopting measures to reduce greenhouse gas emissions which will in turn "minimize oceanic and Arctic warming.""There already is evidence that droughts in the Southwest are partly caused by humans because of the higher temperatures and more evaporation in surface waters like Lake Mead," Lachniet said. "The new fossil-fuel climate might end up making these droughts permanent."
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722134912.htm
|
Climate predictions several years into the future?
|
Our planet's climate system is complex. Different components, like atmosphere, ocean, sea and land ice influence each other and cause natural climate variations on a range of timescales from months to decades. Particularly for the long timescales, the ocean plays an essential role. In a new study published today, a research team led by GEOMAR Helmholtz Centre for Ocean Research Kiel investigates the possibility of utilizing the wind field to predict the North Atlantic surface temperature variations several years into the future. Such variations of the sea surface temperature also have the potential to influence the climate in Europe.
|
'Predictions of climate variations are possible for certain regions on Earth', says Dr. Annika Reintges, scientist at GEOMAR and lead author of the study, that is now published in Are such predictions possible? What are the requirements and which kind of information can be provided by such predictions? These questions were addressed by a research team of GEOMAR and of the Leibniz Institute for Baltic Research Warnemünde. 'Indeed, long-term predictions are possible. This is enabled by the slow, over several years, varying oceanic processes', explains Dr. Reintges. The difficulty is that ocean observations -- that are necessary to start the model computation -- must be as accurate as possible. 'However, ocean observations, in particular below the surface, are limited in quantity and quality' says Reintges.'For the predictions in our study, we did not use any ocean observations. Instead, we create oceanic start values, by prescribing only observed variations in the wind at the sea surface. After some time, this brings the ocean of the model into a state that is sufficiently realistic to start successful predictions for even more than 7 years into the future', explains the author of the study.The research team suggests the following mechanism to explain this fact: The winds cause a change in the ocean circulation. By this, a certain region in the North Atlantic accumulates an anomalous amount of heat. This heat is then transported towards Northeast over a time of several years. This finally results in a warming of the sea surface in the eastern North Atlantic, in response to the winds many years before.'Previous studies have shown that the sea surface temperature of the North Atlantic can influence the European climate. Therefore, such predictions of the North Atlantic surface temperature, covering several years are of great importance also for decision makers in politics, economy, society, and also for the public', Reintges concludes.
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722112743.htm
|
Climate change is impacting the spread of invasive animal species
|
What factors influence the spread of invasive animal species in our oceans? This question was the focus for a team of experts from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Bangor University (Wales, UK), and the University of Greifswald's Zoological Institute and Museum in the context of the DFG-sponsored Research Training Group 2010 RESPONSE (Biological Responses to Novel and Changing Environments). The results of their study have just been released in the journal
|
Crustaceans dominate the food webs of many costal habitats in our oceans. In addition, as 'stowaways' on board of vessels used in global shipping, many crab species have spread far beyond their natural homes. The Asian shore crab Hemigrapsus sanguineus is a good example of these invasive species: in just a few decades this species, native to the Pacific, has spread to many corners of the globe. By the 1980s, it had made its way to the Atlantic coast of North America, and by the 1990s, had gained a foothold in the coastal waters of Europe. In both North America and Northern Europe, this species is spreading farther and farther north, toward the rapidly warming polar waters. In the ecosystems they invade, these crabs can soon reach such high numbers that native species like the European shore crab Carcinus maenas are impacted or displaced. Furthermore, they exert considerable predation pressure in their new homes, often decimating e.g. marine invertebrates like mussels or young shore crabs, and taking these food sources away from other species in the process. This can produce lasting changes to the invaded ecosystems.But how is climate change influencing the spread of invasive marine species? Invasive species are often characterised by a high tolerance for fluctuations in environmental factors like temperature and salinity, thus being more adapted to the effects of climate change in the oceans. The team of researchers, including members from the Alfred Wegener Institute, Bangor University (Wales, UK) and the University of Greifswald, especially focused on the early developmental stages of the Asian shore crab, and examined its microscopically small larvae, which grow as they float in the water column. Since it has been confirmed that the larvae of many marine organisms are more sensitive to environmental fluctuations than their adult counterparts, these larvae often represent a 'bottleneck' in the establishment of new populations.In addition, the study sought to develop models for predicting the speed at which the Asian shore crab could spread northwards, taking climate warming into account. The project's main question: Are findings regarding seasonal influences on larval development helpful for such forecasts? In the study, the team began by measuring the larvae's developmental parameters, e.g. the survival rate and time needed for development at different water temperatures. For this purpose, at the AWI's facilities on Helgoland they studied the duration of their young developmental stages in the lab; and they investigated the occurrence of crab larvae in the field. With the aid of a mechanistic model, the authors were then able to determine the timeframe during the mating season in which the water temperature needs to be above a certain threshold in order for the larvae to successfully develop into juvenile crabs. This modelling indicates considerable potential for the Asian shore crab to spread farther north, along the coasts of Northern England and Norway.According to AWI biologist Dr Gabriela Torres and Dr Luis Giménez, a fellow biologist at the AWI and first author: "Our study confirms that, when it comes to predicting the climate-related spread of marine fauna, we need to especially focus on the early stages of development, as they are critical for the settlement on new habitats and the establishment of new permanent populations." Prof Steffen Harzsch from the University of Greifswald's Zoological Institute and Museum adds: "The Research Training Group RESPONSE offers us an outstanding platform for scientifically investigating various aspects of climate change, through interdisciplinary collaborations that reach far beyond Greifswald."
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722112712.htm
|
Retreat of East Antarctic ice sheet during previous warm periods
|
Questions about the stability of the East Antarctic Ice Sheet are a major source of uncertainty in estimates of how much sea level will rise as the Earth continues to warm. For decades, scientists thought the East Antarctic Ice Sheet had remained stable for millions of years, but recent studies have begun to cast doubt on this idea. Now, researchers at UC Santa Cruz have reported new evidence of substantial ice loss from East Antarctica during an interglacial warm period about 400,000 years ago.
|
The study, published July 22 in Ice flows slowly through the basins from the interior of the continent out to the floating ice shelves at the margins. Ice loss causes the grounding line -- the point at which the ice loses contact with the ground and starts floating -- to shift inland, explained first author Terrence Blackburn, assistant professor of Earth and planetary sciences at UC Santa Cruz."Our data shows that the grounding line in the Wilkes Basin retreated 700 kilometers [435 miles] inland during one of the last really warm interglacials, when global temperatures were 1 to 2 degrees Celsius warmer than now," Blackburn said. "That probably contributed 3 to 4 meters to global sea level rise, with Greenland and West Antarctica together contributing another 10 meters."In other words, a period of global warming comparable to what is expected under current scenarios for humanmade greenhouse gas emissions resulted in an increase in sea level of around 13 meters (43 feet). Of course, this wouldn't happen all at once -- it takes time for that much ice to melt."We've opened the freezer door, but that block of ice is still cold and it's not going anywhere in the short term," Blackburn said. "To understand what will happen over longer time scales, we need to see what happened under comparable conditions in the past."The problem with studying the interglacial periods during the Pleistocene is that they all ended in another ice age when the ice sheet advanced again and covered up the evidence. For the new study, Blackburn and his colleagues used a novel technique based on isotope measurements in mineral deposits that record past changes in subglacial fluids.Uranium-234 (U-234) is an isotope of uranium that accumulates very slowly in water that is in contact with rocks due to the high-energy decay of uranium-238. This happens everywhere, but in most places hydrological processes carry water away from sources of enrichment, and the U-234 gets diluted in large bodies of water. In Antarctica, however, water is trapped at the base of the ice sheet and moves very slowly as long as the ice is stable, allowing U-234 to build up to very high levels over long periods of time.Blackburn explained that the ice sheet acts like an insulating blanket, so that heat from Earth's interior causes melting at the base. But temperatures are colder where the ice is thinner at the margins of the ice sheet, causing subglacial water to refreeze."Water flowing beneath the ice starts refreezing at the edges, which concentrates all the dissolved minerals until it becomes supersaturated and the minerals precipitate out to form deposits of opal or calcite," he said. "Those deposits trap uranium-234, so we can date the deposits and measure their composition, and we can track that through time to get a deep history of the composition of water under the ice sheet."What that history suggests is that the U-234 in subglacial water in the Wilkes Basin was flushed out during the interglacial period 400,000 years ago as the ice melted and the grounding line retreated. That reset the U-234 concentration to low background levels, and accumulation then restarted when the ice advanced again.Blackburn noted that present-day evidence for the accumulation of U-234 in subglacial fluids can be found in the McMurdo Dry Valleys, the only place where Antarctic glaciers terminate on land. There, highly concentrated brines emerge from the glaciers in places such as Blood Falls, where the blood-red color comes from high iron concentrations in the brine."The isotopic compositions of those brines are comparable to the precipitates that we've dated from a range of locations, and they all share the characteristic U-234 enrichment," Blackburn said. "The brines are what's left when the subglacial fluids get all the way to the edge of the ice sheet."He said the new study was inspired by a 2016 paper in which researchers studying deep-sea corals reported evidence of a major change in ocean chemistry, including a spike in U-234, coinciding with the end of the last ice age, when the vast Laurentide Ice Sheet that covered much of North America melted."They speculated that it accumulates under the ice sheets and pointed to some possible sites in Antarctica where that might be happening," Blackburn said. "I happened to be in one of those places at the time."So was his colleague, glaciologist Slawek Tulaczyk, a professor of Earth and planetary sciences at UC Santa Cruz. They discussed the paper and began planning this study, which eventually involved several UCSC faculty and students. The team collected some samples of mineral deposits themselves, but some of the most important samples used in the study were collected in the 1980s and archived at the Byrd Polar Rock Repository at Ohio State University.
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722112648.htm
|
International analysis narrows range of climate's sensitivity to CO2
|
The most advanced and comprehensive analysis of climate sensitivity yet undertaken has revealed with more confidence than ever before how sensitive the Earth's climate is to carbon dioxide.
|
For more than 40 years, the estimated likely range of the eventual global temperature response to a doubling of atmospheric carbon dioxide compared to preindustrial levels has stubbornly remained at 1.5°C -- 4.5°C.This new research, revealed in a 165 page, peer-reviewed journal article commissioned by the World Climate Research Programme (WCRP) written over four years, finds that the true climate sensitivity is unlikely to be in the lowest part of the 1.5-4.5°C range. The analysis indicates that if atmospheric carbon dioxide levels double from their pre-industrial levels and are maintained, the world would probably experience eventual warming from 2.3 -- 4.5°C. The researchers found there would be less than 5% chance of staying below 2°C and a 6-18% chance of exceeding 4.5°C.With the Earth's temperature already at around 1.2°C above preindustrial levels, if greenhouse gas emissions trajectories continue unabated the world can expect to see a doubling of carbon dioxide in the next 60-80 years."Narrowing the range of climate sensitivity has been a major challenge since the seminal US National Research Council paper came up with a 1.5 -- 4.5°C range in 1979 (Charney et al). That same range was still quoted in the most recent IPCC report," said lead author Prof Steven Sherwood, a University of New South Wales chief investigator with the ARC Centre of Excellence for Climate Extremes.The research was only made possible by bringing together an international team of researchers from a wide range of climate disciplines. Using temperature records since the industrial revolution, paleoclimate records to estimate prehistoric temperatures, satellite observations and detailed models that examine the physics of interactions within the climate system the team were able to combine more independent lines of evidence than any previous study to get their results.These lines of evidence were then combined in a statistically rigorous way allowing the team to find where the results overlapped. This allowed them to converge on the best estimate of climate sensitivity. The team found that, with new developments, the various lines of evidence corroborated one another leading to more confidence in the result. The 2.3-4.5°C range accounts cautiously for alternative views or assumptions and "unknown unknowns," with a more straightforward calculation yielding an even narrower 2.6-3.9°C likely range."This paper brings together what we know about climate sensitivity from measurements of atmospheric processes, the historical warming, and warm and cold climates of the past. Statistically combined, these estimates make it improbable that climate sensitivity is at the low end of the IPCC range and confirm the upper range. This adds to the credibility of climate model simulations of future climate," said co-author Gabi Hegerl from the University of Edinburgh."An important part of the process was to ensure that the lines of evidence were more or less independent," said Prof Sherwood. "You can think of it as the mathematical version of trying to determine if a rumour you hear separately from two people could have sprung from the same source; or if one of two eyewitnesses to a crime has been influenced by hearing the story of the other one."The researchers then went another step further and identified the conditions that would be required for the climate sensitivity to lie outside this most likely range.The researchers show that low climate sensitivities previously thought to be plausible, around 1.5-2C, could only occur if there were multiple unexpected and unconnected errors in the data analysis (for example unexpected cloud behaviour and patterns of long-term ocean warming), underlying their judgment that these low values are now extremely unlikely.A different set of circumstances make it unlikely that global temperatures would rise more than 4.5°C for a doubling of carbon dioxide from pre-industrial times, although these higher temperature responses are still more likely than very low sensitivities.Even with this qualification, the three-year long research process initiated by the WCRP with double-checking at every step, a detailed examination of the physical processes and an understanding of the conditions required for the estimate has finally consolidated an advance on the 40-year-problem."These results are a testament to the importance of cross-disciplinary research along with slow, careful science and perfectly highlight how international co-operation can unpick our most vexing problems," said co-author Prof Eelco Rohling from the Australian National University."If international policymakers can find the same focus and spirit of co-operation as these researchers then it will give us hope that we can forestall the worst of global warming."
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722112647.htm
|
Sharks almost gone from many reefs
|
A massive global study of the world's reefs has found sharks are 'functionally extinct' on nearly one in five of the reefs surveyed.
|
Professor Colin Simpfendorfer from James Cook University in Australia was one of the scientists who took part in the study, published today in "This doesn't mean there are never any sharks on these reefs, but what it does mean is that they are 'functionally extinct' -- they are not playing their normal role in the ecosystem," said Professor Simpfendorfer.He said almost no sharks were detected on any of the 69 reefs of six nations: the Dominican Republic, the French West Indies, Kenya, Vietnam, the Windward Dutch Antilles and Qatar."In these countries, only three sharks were observed during more than 800 survey hours," said Professor Simpfendorfer.Dr Demian Chapman, Global FinPrint co-lead and Associate Professor in the Department of Biological Sciences and Institute of Environment at Florida International University, said it's clear the central problem is the intersection between high human population densities, destructive fishing practices, and poor governance."We found that robust shark populations can exist alongside people when those people have the will, the means, and a plan to take conservation action," said Dr Chapman.Professor Simpfendorfer said it was encouraging that Australia was among the best nations at protecting shark populations and ensuring they played their proper role in the environment."We're up there along with such nations as the Federated States of Micronesia, French Polynesia and the US. These nations reflect key attributes that were found to be associated with higher populations of sharks: being generally well-governed, and either banning all shark fishing or having strong, science-based management limiting how many sharks can be caught," he said.Jody Allen, co-founder and chair of the Paul G. Allen Family Foundation which backs the Global FinPrint project, said the results exposed a tragic loss of sharks from many of the world's reefs, but also gave some hope."The data collected from the first-ever worldwide survey of sharks on coral reefs can guide meaningful, long-term conservation plans for protecting the reef sharks that remain," she said.For more information and a new global interactive data-visualized map of the Global FinPrint survey results, visit Global FinPrint is an initiative of the Paul G. Allen Family Foundation and led by Florida International University, supported by a global coalition of partner organizations spanning researchers, funders and conservation groups. The project represents the single largest and most comprehensive data-collection and analysis program of the world's populations of reef-associated sharks and rays ever compiled.
|
Geography
| 2,020 |
July 22, 2020
|
https://www.sciencedaily.com/releases/2020/07/200722083807.htm
|
Plastics found in sea-bed sharks
|
Microplastics have been found in the guts of sharks that live near the seabed off the UK coast.
|
University of Exeter scientists studied four species of demersal (seabed-dwelling) shark.Of the 46 sharks examined, 67% contained microplastics and other human-made fibres.A total of 379 particles were found and -- though the impact on the sharks' health is unknown -- the researchers say it highlights the "pervasive nature of plastic pollution.""Our study presents the first evidence of microplastics and anthropogenic fibre contaminants in a range of native UK demersal shark species," said lead author Kristian Parton, of the Centre for Ecology and Conservation at Exeter's Penryn Campus in Cornwall.Commenting on the possible sources of the particles, he added: "We were surprised to find not only microplastics but also particles such as synthetic cellulose, which is most commonly found in textiles (including disposable hygiene items like facemasks) and clothing."When clothes are washed, or items are discarded as litter, tiny fibres are released and these often flow into water sources and out to sea."Once in the sea, microfibres can either float or sink to the bottom, which is where these sharks live."The fibres could then be ingested via the sharks' food, which is mostly crustaceans, or directly through the sediment on the seabed."In terms of the other types of microplastics we found, many of these may have come from fishing lines or nets."The research team, which included scientists from Greenpeace Research Laboratories, examined the stomachs and digestive tracts of four species: small-spotted catshark, starry smooth-hound, spiny dogfish and bull huss.These species can be found at varying depths from 5-900m, but usually live and feed near the sea floor.Though the study is based on a modest sample size, the findings suggest larger sharks contained more particles. No differences were found based on sex or species.The study was conducted in Cornwall, UK, using sharks caught as "bycatch" (by accident) in a demersal hake fishery, fishing in and around the North-East Atlantic and Celtic Sea.Study co-author Professor Tamara Galloway, of Exeter's Global Systems Institute, said: "We were not expecting to find microfibres from textiles in so many of our native shark species."Our study highlights how important it is to think before we throw things away."Dr Laura Foster, Head of Clean Seas at the Marine Conservation Society, added: "The new research from into these iconic shark species around the UK shows high levels of microplastic ingestion, with 95% of the contaminants found being fibrous."
|
Geography
| 2,020 |
July 21, 2020
|
https://www.sciencedaily.com/releases/2020/07/200721084203.htm
|
Popular seafood species in sharp decline around the world
|
Fish market favourites such as orange roughy, common octopus and pink conch are among the species of fish and invertebrates in rapid decline around the world, according to new research.
|
In the first study of its kind, researchers at the University of British Columbia, the GEOMAR Helmholtz Centre for Ocean Research Kiel and the University of Western Australia assessed the biomass -- the weight of a given population in the water -- of more than 1,300 fish and invertebrate populations. They discovered global declines, some severe, of many popularly consumed species.Of the populations analyzed, 82 per cent were found to be below levels that can produce maximum sustainable yields, due to being caught at rates exceeding what can be regrown. Of these, 87 populations were found to be in the "very bad" category, with biomass levels at less than 20 per cent of what is needed to maximize sustainable fishery catches. This also means that fishers are catching less and less fish and invertebrates over time, even if they fish longer and harder."This is the first-ever global study of long-term trends in the population biomass of exploited marine fish and invertebrates for all coastal areas on the planet," said Maria "Deng" Palomares, lead author of the study and manager of the To reach their findings, the researchers applied computer-intensive stock assessment methods known as CMSY and BSMY to the comprehensive catch data by marine ecosystem reconstructed by the The greatest declines in stocks were found in the southern temperate and polar Indian Ocean and the southern polar Atlantic Ocean, where populations shrunk by well over 50 per cent since 1950.While much of the globe showed declining trends in fish and invertebrates, the analysis found a few exceptions. One of these was the Northern Pacific Ocean where population biomass increased by 800 per cent in its polar and subpolar zones, and by about 150 per cent in its temperate zone.Despite these pockets of improvement, the overall picture remains a cause for concern, according to co-author Daniel Pauly, principal investigator at "Despite the exceptions, our findings support previous suggestions of systematic and widespread overfishing of the coastal and continental shelf waters in much of the world over the last 60-plus years," said Pauly. "Thus, pathways for improvements in effective fisheries management are needed, and such measures should be driven not only by clearly set total allowable annual catch limits, but also by well-enforced and sizeable no-take marine protected areas to allow stocks to rebuild."
|
Geography
| 2,020 |
July 20, 2020
|
https://www.sciencedaily.com/releases/2020/07/200720152413.htm
|
Free trade can prevent hunger caused by climate change
|
Researchers from KU Leuven, the International Institute of Applied Systems Analysis (IIASA) and RTI International investigated the effects of trade on hunger in the world as a result of climate change. The conclusion is clear: international trade can compensate for regional food shortages and reduce hunger, particularly when protectionist measures and other barriers to trade are eliminated.
|
Climate change has consequences for agriculture worldwide, with clear differences between regions. Expectations are that sufficient food will remain available in the Northern hemisphere, but in regions such as Sub-Saharan Africa or South Asia, falling crop yields may lead to higher food prices and a sharp rise in hunger. Further liberalisation of world trade can relieve these regional differences: "If regions like Europe and Latin America, for example, where wheat and corn thrive, increase their production and export food to regions under heavy pressure from global warming, food shortages can be reduced," says doctoral researcher Charlotte Janssens. "It sounds quite obvious, but there are many barriers that complicate this free trade."Import tariffs are a major barrier to international trade in food. They increase the cost of importing basic food crops like wheat, corn or rice. Around a fifth of the worldwide production of these grains is traded internationally. That makes good trade agreements very important in the battle against hunger. Professor Miet Maertens explains: "In the early 21st century, we saw a major liberalisation of the international market. This caused the average import tariffs on agricultural products in Europe, Sub-Saharan Africa and South Asia to drop by a third. Our research shows that this liberalisation makes global food provision less vulnerable to climate change. We also see that further reduction and phasing-out of tariffs can intensify this positive effect."Besides, there are also other barriers. In some countries, the logistical aspect is a sticking point. Roads are sometimes poor or ports are not equipped for loading and unloading large container ships. Countless complicated trade procedures can drive up the effective cost of trade. "A global food strategy must go hand in hand with improvements to trade infrastructure," argues Charlotte Janssens.The international research team, consisting of scientists from KU Leuven, IIASA and RTI International, among others, are making their recommendations based on 60 scenarios. They took into account different forms of trade policy, along with climate change varying from a 2 to 4-degree warming of the Earth. 2050 was set as the horizon for each scenario. "Under the current barriers to trade, the worst-case climate scenario of a 4-degree warming will lead to an extra 55 million people enduring hunger compared to the situation without climate change. If vulnerable regions cannot increase their food imports, this effect will even rise to 73 million," argues Janssens. Where barriers to trade are eliminated, 'only' 20 million people will endure food shortages due to climate change. In the more mild climate scenarios, an intensive liberalisation of trade may even prevent more people from enduring hunger owing to climate change.Yet a liberalisation of international trade may also involve potential dangers. "If South Asian countries would increase rice exports without making more imports of other products possible, they could be faced with increased food shortage within their own borders," warns Charlotte Janssens. "A well thought-out liberalisation is needed in order to be able to relieve food shortages properly.""Sadly enough, we see that in times of crisis, countries are inclined to adopt a protectionist stance. Since the start of the current corona crisis, around ten countries are closing their borders for the export of important food crops," says Janssens. "In the context of climate change, it is highly important that they avoid such protectionist behaviour and instead continue to maintain and utilise the international trade framework."
|
Geography
| 2,020 |
July 20, 2020
|
https://www.sciencedaily.com/releases/2020/07/200720152407.htm
|
South Atlantic anomalies existed 8 - 11 million years ago
|
Research by the University of Liverpool has revealed that strange behaviour of the magnetic field in the South Atlantic region existed as far back as eight to 11 million years ago, suggesting that today's South Atlantic Anomaly is a recurring feature and unlikely to represent an impending reversal of the Earth's magnetic field.
|
The South Atlantic Anomaly is an area characterized by a significant reduction in the strength of Earth's magnetic field compared with areas at similar geographic latitudes. Here, protection from harmful radiation from space is reduced. The most significant signs of this are technical malfunctions aboard satellites and spacecraft.In a study published in the The geomagnetic records from the rocks covering 34 different volcanic eruptions that took place between eight and 11 million years ago revealed that at these occurrences the direction of the magnetic field for St Helena often pointed far from the North pole, just like it does today.The Earth's magnetic field, or the geomagnetic field, not only gives us the ability of navigating with a compass, but also protects our atmosphere from charged particles coming from the sun, called solar wind. However, it is not completely stable in strength and direction, both over time and space, and it has the ability to completely flip or reverse itself with substantial implications.The South Atlantic Anomaly is a topic of debate between scientists in this field. Besides the fact that it causes damages to space technology, it also raises the question of where it comes from and whether it represents the start of the total weakening of the field and a possible upcoming pole reversal.Lead author of the paper, University of Liverpool PhD student Yael Engbers, said: "Our study provides the first long term analysis of the magnetic field in this region dating back millions of years. It reveals that the anomaly in the magnetic field in the South Atlantic is not a one-off, similar anomalies existed eight to 11 million years ago."This is the first time that the irregular behaviour of the geomagnetic field in the South Atlantic region has been shown on such a long timescale. It suggests that the South Atlantic Anomaly is a recurring feature and probably not a sign of an impending reversal."It also supports earlier studies that hint towards a link between the South Atlantic Anomaly and anomalous seismic features in the lowermost mantle and the outer core. This brings us closer to linking behaviour of the geomagnetic field directly to features of the Earth's interior"
|
Geography
| 2,020 |
July 20, 2020
|
https://www.sciencedaily.com/releases/2020/07/200720145917.htm
|
Changes in farming urgent to rescue biodiversity
|
Over 360 scientists from 42 countries -- led by the University of Göttingen and Westlake University China -- call for transition of food production systems to agroecological principles.
|
Humans depend on farming for their very survival but this activity takes up more than one third of the world's landmass and endangers 62% of all threatened species globally. However, agricultural landscapes can support, rather than damage, biodiversity, but only through a global transition to agroecological production. An international team of over 360 scientists from 42 countries, led by the University of Göttingen and Westlake University in China, argue that agroecological principles should be integrated in the post-2020 Global Biodiversity Framework, which aims to reduce threats to biodiversity and will be decided at the 15th Convention of the Parties (COP15) meeting in China. Their Correspondence article was published in Reversing the trend in species decline is essential for the benefit of both people and the planet, but it will require coordinated actions and sustainable agriculture. Intensive farming relying on excessive pesticides and fertiliser has negative effects on biodiversity. The authors argue that farming landscapes can provide habitats for biodiversity, promote connectivity between protected areas and increase species' ability to respond to environmental threats. The authors' research agenda includes enhancing global research networks, expanding technical innovation and improving communication. The authors emphasise the importance of working with and supporting farmers, indigenous people and local communities. Diversification in crops together with new varieties and combinations, for instance, can sustain yields. In addition, these actions can support biodiversity and ecosystems whilst providing more nutritious and healthy food for all.This year is crucial for biodiversity, not just because time is running out to conserve insects and other wildlife, but also because the 15th Convention of the Parties (COP15) will meet in China for the UN Biodiversity Conference, now in 2021 due to COVID-19. At COP15, the post-2020 Global Biodiversity Framework will be agreed which has targets to reduce threats to biodiversity. The authors have elaborated how agroecological principles can help meet each of these targets.Dr Thomas Cherico Wanger from Westlake University China and University of Göttingen and first author of the correspondence reports, "The importance of agroecology to change agriculture and protect biodiversity has been recognized by many top level organizations, in the scientific community, and by practitioners, which is also reflected in the number and affiliations of signatories of our Correspondence. Following our positive discussions with representatives of the COP15, I hope that this correspondence can help to stimulate discussions in the policy arena and make a real impact on agricultural production systems."Professor Teja Tscharntke, co-author and Head of the Agroecology Research Group at the University of Göttingen, adds: "Agroecology has the potential to change the way we 'do agriculture'. We hope that our comprehensive research agenda will help to chart the path to sustainable, diversified agriculture and biodiversity conservation in the future."
|
Geography
| 2,020 |
July 20, 2020
|
https://www.sciencedaily.com/releases/2020/07/200720112338.htm
|
Geoscientists glean data suggesting global climate changes increase river erosion rates
|
Scientists have long debated the idea that global climate changes have forced river erosion rates to increase over the past five million years. New field data gleaned from a multi-institution, collaborative study of North America's rugged Yukon River basin, near storied Klondike goldfields, reveal profound increases in river erosion during abrupt global intensification of climate fluctuations about 2.6 and one million years ago.
|
"These results provide the first definitive support that increases in sediment deposited to oceans from river erosion coincide with dramatic changes in glacial cycles," says Utah State University geoscientist Tammy Rittenour. "Our ability to date former river deposits was the game-changing factor in allowing us to pursue this hypothesis."Rittenour and colleagues from the U.S. Geological Survey, the University of Vermont and Purdue University published findings in the July 20, 2020, issue of "Oxygen isotope values in marine sediment show worldwide fluctuations between cold and warm climates that abruptly intensified during the early Pleistocene period," says Rittenour, professor in USU's Department of Geosciences. "Rates of river sediment accumulation also jumped during this time."Since rivers do the work of erosion and sediment transport over most of the Earth's surface, scientists have long suggested patterns of global precipitation mimic climate fluctuations."If that's the case, enhanced river discharge resulting from intensified global precipitation would increase rates of river erosion," she says.To test this idea, the team took advantage of the landscape history preserved in the study site's prominent river terraces -- ancient river floodplains -- perched up to hundreds of meters above the modern Fortymile River, a Yukon River tributary that flows from northwestern Canada to Alaska."This 'Rosetta-stone' location, with exposed terraces, provided a long-sought window from which to obtain data," says Rittenour, a Geological Society of America Fellow. "We geochronologists often repeat the adage, 'No Dates, No Rates,' meaning we can't calculate rates of erosion without age control. Using relatively new dating techniques, we were able, for the first time, to establish ages for river deposits that span these key time periods of global climate change."Co-authors Lee Corbett and Paul Bierman of UVM and Marc Caffee of Purdue provided age control on the site's older terraces, using cosmogenic nuclide burial dating methods that use differing decay rates of unique radiogenic isotopes of beryllium and aluminum produced by sediment exposure to cosmic radiation.Rittenour, director of USU's Luminescence Laboratory, used optically stimulated luminescence dating of younger river sediments."OSL dating provides an age estimate of the last time the sediment was exposed to light," she says.Corroborating the team's new results, Bering Sea sediment records show concurrent increases in accumulation of sediment eroded from the Fortymile River."It's exciting to apply new tools to test foundational ideas that have been only previously speculated," Rittenour says. "These results represent an important step toward understanding the influence of climate in shaping landscapes inhabited by people, and provide clues regarding future landscape response to human activity."
|
Geography
| 2,020 |
July 20, 2020
|
https://www.sciencedaily.com/releases/2020/07/200720112335.htm
|
Plant roots increase carbon emission from permafrost soils
|
A key uncertainty in climate projections is the amount of carbon emitted by thawing permafrost in the Arctic. Plant roots in soil stimulate microbial decomposition, a mechanism called the priming effect. An international research team co-lead by Frida Keuper from INRAE and Umeå University and Birgit Wild from Stockholm University shows that the priming effect alone can cause emission of 40 billion tonnes carbon from permafrost by 2100. The study was published today in
|
Permafrost is permanently frozen ground which stores as much carbon as there is in all plants on Earth and in the atmosphere together. The surface of the permafrost thaws in summer, allowing plant and soil life to thrive. When microorganisms breathe, they emit greenhouse gases. Scientists have previously anticipated that rapidly rising temperatures will drive the emission of 50-100 billion ton permafrost carbon by 2100. On top of that, plant roots feed sugar to the microorganisms in the soil, which the microbes can use to break down more soil organic matter -- the priming effect -- resulting in even higher greenhouse gas emissions."We have known about the priming effect since the 1950's, but we did not know whether or not this small-scale ecological interaction had a significant impact on the global carbon cycle," says Research Scientist Frida Keuper, affiliated with the French National Research Institute for Agriculture, Food and Environment, INRAE, and with Umeå University, Sweden.The team of researchers combined maps of plant activity and data on soil carbon content from the Northern Circumpolar Soil Carbon Database with an extensive literature survey on priming and plant root properties, to estimate the priming effect in permafrost ecosystems and its influence on greenhouse gas emissions.They show that the priming effect increases soil microbial respiration by 12 percent, which causes the additional loss of 40 billion ton carbon by 2100 compared to current predictions for permafrost. This equals almost a quarter of the remaining 'carbon budget' for human activities to limit global warming to max 1.5°C."These new findings demonstrate how important it is to consider small-scale ecological interactions, such as the priming effect, in global greenhouse gas emission modelling," says Birgit Wild, Assistant Professor at Stockholm University.
|
Geography
| 2,020 |
July 20, 2020
|
https://www.sciencedaily.com/releases/2020/07/200720104556.htm
|
Using techniques from astrophysics, researchers can forecast drought up to ten weeks ahead
|
Researchers at the University of Sussex have developed a system which can accurately predict a period of drought in East Africa up to ten weeks ahead.
|
Satellite imagery is already used in Kenya to monitor the state of pastures and determine the health of the vegetation using a metric known as the Vegetation Condition Index. These are conveyed to the decision makers in arid and semi-arid regions of Kenya through drought early warning systems.However, these systems, operated by the National Drought Management Authority (NDMA), only allows organisations and communities to intervene when the impacts of a drought have already occurred. By that point, such extreme weather would already have had a devastating effect on the livelihood of local people.Instead, a team of researchers from the University of Sussex and the NDMA have developed a new system called Astrocast.Part-funded by the Science and Technology Facilities Council, the project allows humanitarian agencies and drought risk managers to be proactive when it comes to dealing with the impacts of extreme weather by forecasting changes before they occur.In a research paper published in Dr Pedram Rowhani, Senior Lecturer in Geography and co-founder of Astrocast, said: "In many cases, the first signs of a drought can be seen on natural vegetation, which can be monitored from space."Our approach measures past and present Vegetation Condition Index (VCI), an indicator that is based on satellite imagery and often used to identify drought conditions, to understand trends and the general behaviour of the VCI over time, to predict what may happen in the future."Joint first author on the paper and Lecturer in Machine Learning and Data Science, Dr Adam Barrett said: "After conversations in corridors with Dr Rowhani about AstroCast, I saw an opportunity to apply methodology I'd been developing in theoretical neuroscience to a project with potential for real humanitarian impact."With Sussex actively encouraging interdisciplinary working, we decided to combine skillsets. It's been eye-opening to see how our techniques can be applied to a real-world problem and improve lives."There has been a growing demand within the humanitarian sector to develop systems that focus on advance warnings and encourage a more proactive approach to disasters.The Kenyan NDMA already provides monthly drought bulletins for every county, which state detected changes in the vegetation and are used to make decisions about whether to declare a drought alert.But with Astrocast forecasts, these bulletins could also include a prediction of what the VCI is likely to be in a few weeks' time, giving farmers and pastoralist valuable time to prepare.Seb Oliver, Professor of Astrophysics and co-founder of Astrocast, said: "A large part of my astrophysics research requires processing data from astronomical space telescopes, like the Herschel Space Observatory. Earth observation satellites are not that different."We often use cutting-edge statistics and machine-learning approaches to interpret our astronomical data. In this case we've used machine-learning approaches, and we've been able to forecast the state of the vegetation up to ten weeks ahead with very good confidence."We imagine that our reports might be used to define a new warning flag allowing county leaders to make decisions earlier and so prepare better. But this information could also be used by humanitarian organisations like the Kenya Red Cross as well as other organisations like the Kenya Met Department."Earlier preparation is well known to be much more effective than reactive response."
|
Geography
| 2,020 |
July 17, 2020
|
https://www.sciencedaily.com/releases/2020/07/200717120155.htm
|
Antarctica more widely impacted by humans than previously thought
|
Antarctica is considered one of the Earth's largest, most pristine remaining wildernesses. Yet since its formal discovery 200 years ago, the continent has seen accelerating and potentially impactful human activity.
|
How widespread this activity is across the continent has never been quantified. We know Antarctica has no cities, agriculture or industry. But we have never had a good idea of where humans have been, how much of the continent remains untouched or largely unimpacted, and to what extent these largely unimpacted areas serve to protect biodiversity.A team of researchers led by Monash University, including Dr Bernard Coetzee from the Global Change Institute at the University of the Witwatersrand, Johannesburg (Wits University), has changed all of that. Using a data set of 2.7 million human activity records, the team showed just how extensive human use of Antarctica has been over the last 200 years. The research was published in the journal With the exception of some large areas mostly in the central parts of the continent, humans have set foot almost everywhere.Although many of these visited areas have only been negligibly affected by people, biodiversity is not as well represented within them as it should be."We mapped 2.7 million human activity records from 1819 to 2018 across the Antarctic continent to assess the extent of wilderness areas remaining and its overlap with the continent's biodiversity," says Coetzee, a conservation scientist at Wits University. Based in Skukuza in the Kruger National Park in South Africa, Coetzee helped conceptualise the study and collated a spatial database from multiple sources to map the extent of human activity in Antarctica."In a region often thought of as remote, we showed that in fact human activity has been extensive, especially in ice-free and coastal areas where most of its biodiversity is found. This means that "wilderness" areas do not capture many of the continent's important biodiversity sites, but that an opportunity exists to conserve the last of the wild."The study found that only 16% of the continent's Important Bird Areas, areas identified internationally as critical for bird conservation, are located within negligibly impacted areas, and little of the total negligibly impacted area is represented in Antarctica's Specially Protected Area network.High human impact areas, for example some areas where people build research stations or visit for tourism, often overlap with areas important for biodiversity.Lead author, Rachel Leihy, a PhD student in the Monash School of Biological Sciences, points out that "While the situation does not look promising initially, the outcomes show that much opportunity exists to take swift action to declare new protected areas for the conservation of both wilderness and biodiversity.""Informatics approaches using large data sets are providing new quantitative insights into questions that have long proven thorny for environmental policymakers," says Steven Chown, the corresponding author based at Monash University."This work offers innovative ways to help the Antarctic Treaty Parties take forward measures to secure Antarctica's Wilderness."The transdisciplinary team delivering this work includes researchers from Australia, the Netherlands, New Zealand, and South Africa.
|
Geography
| 2,020 |
July 17, 2020
|
https://www.sciencedaily.com/releases/2020/07/200717120132.htm
|
Baleen whales have changed their distribution in the Western North Atlantic
|
Researchers have been using passive acoustic recordings of whale calls to track their movements. They have found that four of the six baleen whale species found in the western North Atlantic Ocean -- humpback, sei, fin and blue whales -- have changed their distribution patterns in the past decade. The recordings were made over 10 years by devices moored to the seafloor at nearly 300 locations from the Caribbean Sea to western Greenland.
|
"All four whale species were present in waters from the southeast U.S. to Greenland, with humpbacks also present in the Caribbean Sea," said Genevieve Davis, a senior acoustician at the Northeast Fisheries Science Center in Woods Hole, Massachusetts and lead author of the study. "These four species were detected throughout all the regions in the winter, suggesting that baleen whales are widely distributed during these months. Humpback, sei, fin, and blue whales also showed significant changes in where they were detected between the two time periods considered in this study: before and after 2010."A large group of federal, state and academic researchers from the United States and Canada conducted the study, published in Data collected from 2004 to 2014 on 281 bottom-mounted passive acoustic recorders totaled 35,033 days of recording. These passive acoustic recorders were deployed between the tiny island of Saba in the Caribbean Sea to the Davis Strait off western Greenland. Recorders were located on the continental shelf or along the shelf edge, with six recording units in off-shelf waters.All available passive acoustic recordings from more than 100 research projects throughout the western North Atlantic Ocean were combined to create the decade-long dataset. The time series was split between 2004 to 2010 and 2011 to 2014. That split was based on the timing of shifts in climate in the Gulf of Maine and distribution changes by numerous species in the western North Atlantic Ocean.This is also the same time period used in a similar analysis of North Atlantic right whales that was published in 2017, and used for comparison with this study.Results show that fin, blue, and sei whales were more frequently detected in the northern latitudes after 2010 but less on the Scotian Shelf area. This matches documented shifts in prey availability in that region."The Gulf of Maine, an important feeding ground for many baleen whale species, is warming faster than most places in the world, resulting in changes in distribution not only of marine mammals and fish but also for their prey," said Davis, who was also the lead author of the 2017 North Atlantic right whale study. "These changes in distribution for five of the six baleen whale species mirrors known shifts in distribution for other species attributed to climate and the impacts of ocean warming."Researchers have not yet studied if or how minke whale distribution has shifted. Minkes are the sixth baleen whale species found in the western North Atlantic Ocean.Researchers caution that while recorders provided widespread coverage, there were gaps. Also, these data can confirm where and when a species is present, but not how many individuals are present. There are differences in vocal behavior, seasonal changes, and vocalizations thought to be made by males only. The data provide a comprehensive overview of the minimum distribution in space and time of each species and add information to the current understanding of these species.While humpback whales are found in all regions, researchers were a bit surprised at the length of time they are present in all areas. Fin, blue, and sei whales increased the time that they spent in northern latitudes after 2010, perhaps following prey. All but sei whales had a decreased acoustic presence on the Scotian Shelf after 2010.Sei whales, one of the least-studied baleen whales, were detected with the other whale species from Florida to eastern Greenland. Sei whales are found year-round in Southern New England and the New York Bight. These are also important regions for other baleen whale species, including North Atlantic right whales that target the same prey as sei whales."This study is the first comprehensive analysis of sei whale distribution throughout the western North Atlantic Ocean, including their movements and important habitat," Davis said. "The southern limit of their range remains unknown, and their migratory movements in the western North Atlantic are still not well understood but we have filled in a number of information gaps."Fin whales were detected nearly year-round from Virginia to eastern Greenland. They are commonly found year-round in the Gulf of Maine and in Canadian waters off Nova Scotia. Acoustic records revealed their year-round presence in Massachusetts Bay and the New York Bight. New England waters provide feeding grounds, but mating and calving grounds are unknown. Their distribution year-round suggests that, like other baleen whales, not all fin whales migrate.Blue whales are seen and heard year-round in and around the Gulf of St. Lawrence, where their population is well-studied. Considered a more northern whale, they have occasionally been sighted in the Gulf of Maine. Acoustic detections revealed blue whales are present as far south as North Carolina.Blue whales tend to use deeper waters, making their seasonal movements difficult to study. Satellite tag studies, however, indicate they move from the Gulf of St. Lawrence to North Carolina, including on and off the continental shelf. They also move into deeper waters around the New England Seamounts -- a chain of underwater extinct volcanoes that extends from Georges Bank southeast for about 700 miles. Researchers found the shelf break and canyons to be important habitat areas for blue whales."A decade of acoustic observations have shown important changes over the range of baleen whales and identified new habitats that will require further protection from human-induced threats like fixed fishing gear, shipping, and noise pollution," said Davis.
|
Geography
| 2,020 |
July 16, 2020
|
https://www.sciencedaily.com/releases/2020/07/200716163033.htm
|
Scientists identify new species of sea sponge off the coast of British Columbia, Canada
|
Deep in the inky ocean abyss off the coast of British Columbia, reefs made of glass sea sponges cover hundreds of kilometres of the ocean floor. The sponges form multi-storied habitats, their glass skeletons stacked on top of one another to create intricate reefs. And while their description may sound otherworldly, these reefs are home to creatures with whom we are very familiar, including halibut, rockfish, and shrimp.
|
In February 2017, Fisheries and Oceans Canada designated this region -- including Hecate Strait and Queen Charlotte Sound -- a marine protected area in order to preserve the delicate, glass reefs. But to effectively manage conservation efforts, scientists must develop a better understanding of the lifeforms that are already there."One of the most important reasons for studying the diversity of sea sponges in our oceans is for conservation management," explained Lauren Law, who conducted this research as part of her graduate studies with Sally Leys, professor in the University of Alberta's Department of Biological Sciences. "Many studies in the protected area have focused on describing the crustaceans and fish living in the reefs, but non-reef forming sponges remain overlooked."Now, the UAlberta research team has published a study on the discovery of a new sponge that is abundant in the region, making up nearly 20 per cent of the live sponges in the reefs off the coast of British Columbia. The new species -- called Desmacella hyalina -- was discovered using an underwater robot that travelled along the ocean floor, surveying reefs and collecting samples."Our findings show Desmacella comprise a surprisingly large amount of live sponge cover in the reefs and can have potential major influence on reef function, recruitment, and overall ecosystem health," said Law, who is now a biologist with Fisheries and Oceans Canada Pacific Region. "While we have discovered a new species, we have yet to determine its relationship with glass sponges in the area."The researchers recommend further investigation to better understand the role of Desmacella in the ecosystem, as well as more ecological assessment of glass sponge habitat focused on surveying non-reef forming sponges."Properly knowing the components of an environment and the linkages between them -- here this new species Desmacella hyalina and the reef sponges it lives on -- is a major step forward in understanding the ecosystem services and function of the sponge reefs," added Leys. "This is the information we need for concrete management strategies."
|
Geography
| 2,020 |
July 16, 2020
|
https://www.sciencedaily.com/releases/2020/07/200716120705.htm
|
Divining monsoon rainfall months in advance with satellites and simulations
|
Researchers affiliated with The University of Texas at Austin have developed a strategy that more accurately predicts seasonal rainfall over the Asian monsoon region and could provide tangible improvements to water resource management on the Indian subcontinent, impacting more than one fifth of the world's population.
|
Using satellite data on the size and extent of the snow pack on the Tibetan plateau and in Siberia, the team created better climate model simulations that predict variation in monsoon rainfall the following season. The new research was published online in "We are focusing on the time scale beyond the 14 days of weather forecasting to a farther, seasonal outlook," said Peirong Lin, currently a postdoc at Princeton University who helped lead this research project while a graduate student at UT Jackson School of Geosciences. "This is a very important time scale because water resource managers need to know the forecast months prior to the monsoon onset for decisions about resources and agriculture."Monsoon winds and the rain that comes with them are propelled by the temperature difference between land and ocean. Current climate forecasting relies on computer models that use general circulation models, soil moisture and other factors. The new model uses complementary satellite data to improve these forecasts by revisiting a historically recognized link between snow pack characteristics and monsoon strength over the Asian monsoon region, especially on the Indian subcontinent."For Indian monsoons, it was empirically known almost 140 years ago that rainfall in the summer was connected to snowpack in the Himalaya," said Zong-Liang Yang, professor in the Jackson School's Department of Geological Sciences. "But with our new model, we now have a deeper understanding of the interconnected processes, and we are able to quantify such connection that predicts monsoon season strength from snow pack."The new research uses both the breadth and depth of winter snows to more accurately simulate monsoons. The information constraining the new models comes from two satellites: the Moderate Resolution Imaging Spectroradiometer (MODIS) that provides data about snow cover, and the Gravity Recovery and Climate Experiment (GRACE) with gravitational information that determines the depth of snow. Combined, the observations make the modeled snow conditions more realistic and demonstrate that heavy snow pack -- with slower heating of landmass in comparison to the ocean -- leads to weaker monsoons. Conversely, milder winter snows lead to stronger monsoons.The research also finds that snow in Tibet and Siberia have different roles in moderating monsoon rainfall. The snow on the Tibetan plateau is relatively thin compared to Siberia's. Detailed analysis in the research paper shows that the Tibetan snow pack improves a few weeks of forecasting. It is the Siberian snow that melts later in the summer, thereby having a longer impact on the climate system, that influences predictions with greater lead time and further into peak monsoon season.There are caveats to this research. Monsoons impact a far wider region of the world, but the team's simulations showed the most pronounced forecasts were obtained only in the Indian subcontinent, and they were not as effective over East Asia."The forecast is mostly improved over the Indian subcontinent likely because Indian monsoon is more sensitive to snow changes on land," said Lin. "The East Asian monsoon may be more complex."Still, the team hopes that the new strategy developed by their research will be used to improve seasonal forecasts beyond the Indian subcontinent, with future research that expands the current simulations."The work that we accomplished at the Jackson School is leading the field, but it will take time before these ideas are implemented in operational modeling systems in operational centers," said Yang. "But our goal is to decrease the research-to-operation gap and find ways to use many of the underutilized satellites that can inform long-term weather prediction."Additional authors of this research include Jiangfeng Wei, currently affiliated with Nanjing University of Information Science and Technology in China; Robert E Dickinson of the Jackson School of Geosciences; Yongfei Zhang, currently affiliated with Program in Atmospheric and Oceanic Sciences at Princeton University; and Long Zhao, currently affiliated with Southwest University in Chongqing, China. All research by all authors was done while affiliated with the Jackson School of Geosciences.
|
Geography
| 2,020 |
July 16, 2020
|
https://www.sciencedaily.com/releases/2020/07/200716111631.htm
|
Sea turtles' impressive navigation feats rely on surprisingly crude 'map'
|
Since the time of Charles Darwin, scientists have marveled at sea turtles' impressive ability to make their way -- often over thousands of kilometers -- through the open ocean and back to the very places where they themselves hatched years before. Now, researchers reporting in the journal
|
"By satellite tracking turtles travelling to small, isolated oceanic islands, we show that turtles do not arrive at their targets with pinpoint accuracy," says Graeme Hays of Australia's Deakin University. "While their navigation is not perfect, we showed that turtles can make course corrections in the open ocean when they are heading off-route. These findings support the suggestion, from previous laboratory work, that turtles use a crude true navigation system in the open ocean, possibly using the earth's geomagnetic field."Despite much study of sea turtle navigation, many details were lacking. Hays' team realized that was in part because most sea turtles return to spots along the mainland coast, which are also the easiest places to find.For the new study, his team had attached satellite tags to nesting green turtles (Chelonia mydas) out of an interest in learning about the extent of the turtles' movements and to identify key areas for conservation. In the process, they realized that, by serendipity, many of the tracked turtles travelled to foraging sites on isolated islands or submerged banks. It allowed them to explore in more detail how turtles make their way to such small and harder-to-find islands.In total, the researchers recorded the tracks of 33 green sea turtles migrating across the open ocean from their nesting beaches on the island of Diego Garcia (Indian Ocean) to their foraging grounds across the western Indian Ocean, many of which were isolated island targets. Using individual-based models that incorporated ocean currents, they then compared actual migration tracks against candidate navigational models to show that 28 of the 33 turtles didn't re-orient themselves daily or at fine-scales.As a result, the turtles sometimes travelled well out of their way -- several hundred kilometers off the direct routes to their goal -- before correcting their direction, often in the open ocean. Frequently, they report, turtles did not reach their small island destinations with pinpoint accuracy. Instead, they often overshot and or spent time searching for the target in the final stages of migration."We were surprised that turtles had such difficulties in finding their way to small targets," Hays says. "Often they swam well off course and sometimes they spent many weeks searching for isolated islands."We were also surprised at the distance that some turtles migrated. Six tracked turtles travelled more than 4,000 kilometers to the east African coast, from Mozambique in the south, to as far north as Somalia. So, these turtles complete round-trip migrations of more than 8,000 kilometers to and from their nesting beaches in the Chagos Archipelago."The findings lend support to the notion that migrating sea turtles use a true navigation system in the open ocean. They also provide some of the best evidence to date that migrating sea turtles have an ability to re-orient themselves in deep waters in the open ocean, the researchers say. This implies that they have and rely on a map sense. But the results also show that their map lacks fine details, allowing them to operate only at a crude level.As a result of this imperfect navigation system, the turtles reach their destination only imperfectly. In the process, the turtles spend extra energy and time searching for small islands.The findings also have implications for the turtles' conservation, Hays says. Turtles travel broadly across the open ocean once nesting season has finished. As a result, he says, "conservation measures need to apply across these spatial scales and across many countries."The researchers say that they hope the next generation of tag technology will allow them to directly measure the compass heading of migrating turtles as well as their location. "Then we can directly assess how ocean currents carry turtles off-course and gain further insight into the mechanisms that allow turtles to complete such prodigious feats of navigation," Hays says.
|
Geography
| 2,020 |
July 16, 2020
|
https://www.sciencedaily.com/releases/2020/07/200716101610.htm
|
Dehydration increases amphibian vulnerability to climate change
|
Amphibians have few options to avoid the under appreciated one-two punch of climate change, according to a new study from Simon Fraser University researchers and others.
|
Rising summer temperatures are also resulting in higher rates of dehydration among wet-skinned amphibians as they attempt to keep themselves cool.Researchers from SFU and the University of California-Santa Cruz predict that by the 2080s, habitats previously thought to be safe for amphibians will either be too hot or too dehydrating for them to inhabit. Even the edges of wetlands may be too hot for up to 74 percent of the summer and that sunny, dry spots will be too dehydrating for up to 95 percent of the summer.The study was published yesterday in the journal Researchers studied the environmental conditions in shaded and damp nooks and crannies at the edges of wetlands in the mountains of the Pacific Northwest. They sought to predict how suitable those environments will be for amphibians in the future.These findings are significant because most previous research on the effects of climate change on amphibians has focused solely on temperature, ignoring an equally important physiological process for amphibians -- evaporative water loss.By incorporating rates of water loss, the researchers found that previous studies may have dramatically underestimated the already dire predictions of climate change impacts on amphibians.Instead of subjecting live amphibians to invasive measurements, the researchers estimated water loss rates and internal body temperatures using model frogs made of agar (seaweed extract) that closely mimic the water loss and temperatures of live amphibians.These model frogs were placed in four habitats that encompass the behavior of many different amphibian species -- shaded locations on land and in shallow wetlands, and sun exposed locations on land and in shallow wetlands.The data was related to key environmental conditions, including air temperature, precipitation, and relative humidity, and then linked to forecasts of future climate change.The study also found that amphibians face a difficult trade-off: animals in cool shaded places on dry land face harmful rates of dehydration, and those in shallow water face harmful high temperatures."Such trade-offs will only get more challenging with future climate change, with no single habitat being safe at all times," says Gavia Lertzman-Lepofsky, the study's lead author.This also means that to remain within their environmental limits, frogs and salamanders will have to move between habitats much more often, using up energy for movement rather than for finding food.Unfortunately, the larger landscape surrounding amphibians is also changing. As individuals become more dependent on finding damp and shaded spots to escape the heat, there will also be less water available in the landscape as small ponds and wetlands dry up over the long, dry summers.This puts increasing pressure on populations and provides a sobering view of how amphibians will survive in a hotter, drier world.
|
Geography
| 2,020 |
July 15, 2020
|
https://www.sciencedaily.com/releases/2020/07/200715142348.htm
|
Marine drifters: Interdisciplinary study explores plankton diversity
|
Ocean plankton are the drifters of the marine world. They're algae, animals, bacteria, or protists that are at the mercy of the tide and currents. Many are microscopic and hidden from view, barely observable with the naked eye. Though others, like jellyfish, can grow relatively large.
|
There's one thing about these drifting critters that has puzzled ecologists for decades -- the diversity among ocean plankton is much higher than expected. Generally, in any given ocean sample, there are many rare species of plankton and a small number of abundant species. Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have published a paper in "For years, scientists have been asking why there are so many species in the ocean," said Professor Simone Pigolotti, who leads OIST's Biological Complexity Unit. Professor Pigolotti explained that plankton can be transported across very large distances by currents, so they don't seem to be limited by dispersal. This would suggest that niche preference is the factor that determines species diversity -- in other words, a single species will outcompete all other species if the environment suits them best, leading to communities with only a few, highly abundant species."Our research explored the theory that ocean currents promote species diversity, not because they help plankton to disperse, but because they can actually limit dispersal by creating barriers," said Professor Pigolotti. "In contrast, when we looked at samples from lakes, where there are little or no currents, we found more abundant species, but fewer species altogether."At first glance, this might seem counter-intuitive. But while currents may carry plankton from one area to another, they also prevent the plankton from crossing to the other side of the current. Thus, these currents reduce competition and force each species of plankton to coexist with other species, albeit in small numbers.For over a century, ecologists have measured diversity by counting the number of species, such as birds or insects, in an area. This allowed them to find the proportions of abundant species versus rare species. Today, the task is streamlined through both quantitative modelling that can predict species distributions and metagenomics -- instead of just counting species, researchers can efficiently collect all the DNA in a sample."Simply counting the amount of species in a sample is very time consuming," said Professor Tom Bourguignon, who leads OIST's Evolutionary Genomics Unit. "With advancements in sequencing technologies, we can run just one test and have several thousand DNA sequences that represents a good estimation of planktonic diversity."For this study, the researchers were particularly interested in protists -- microscopic, usually single-celled, planktonic organisms. The group created a mathematical model that considered the role of oceanic currents in determining the genealogy of protists through simulations. They couldn't just simulate a protist community at the DNA level because there would be a huge number of individuals. So, instead, they simulated the individuals in a given sample from the ocean.To find out how closely related the individuals were, and whether they were of the same species, the researchers then looked back in time. "We created a trajectory that went back one hundred years," said Professor Pigolotti. "If two individuals came from a common ancestor in the timescale of our simulation, then we classed them as the same species."What they were specifically measuring was the number of species, and the number of individuals per species. The model was simulated with and without ocean currents. As the researchers had hypothesized, it showed that the presence of ocean currents caused a sharp increase in the number of protist species, but a decline in the number of individuals per species.To confirm the results of this model, the researchers then analyzed datasets from two studies of aquatic protists. The first dataset was of oceanic protists' DNA sequences and the second, freshwater protists' DNA sequences. They found that, on average, oceanic samples contained more rare species and less abundant species and, overall, had a larger number of species. This agreed with the model's predictions."Our results support the theory that ocean currents positively impact the diversity of rare aquatic protists by creating these barriers," said Professor Pigolotti. "The project was very interdisciplinary. By combining theoretical physics, marine science, and metagenomics, we've shed new light on a classic problem in ecology, which is of relevance for marine biodiversity."
|
Geography
| 2,020 |
July 15, 2020
|
https://www.sciencedaily.com/releases/2020/07/200715142333.htm
|
Study first to show tiger sharks' travels and desired hangouts in the Gulf of Mexico
|
Like other highly migratory sharks, tiger sharks (Galeocerdo cuvier) often traverse regional, national and international boundaries where they encounter various environmental and humanmade stressors. Their range and habitat use in the Gulf of Mexico, a complex marine environment significantly impacted by the Deepwater Horizon Oil Spill in 2010, has been understudied and remains unknown.
|
Using sophisticated satellite telemetry, a study is the first to provide unique insights into how tiger sharks move and use habitats in the Gulf of Mexico across life-stages. Data from the study, just published in For the study, Matt Ajemian, Ph.D., lead author and an assistant research professor at Florida Atlantic University's Harbor Branch Oceanographic Institute, and a team of scientists examined size and sex-related movement and distribution patterns of tiger sharks in the Gulf of Mexico. They fitted 56 tiger sharks with Smart Position and temperature transmitting tags between 2010 -- following the Deepwater Horizon Oil Spill -- and 2018 -- spanning shelf waters from south Texas to south Florida and examined seasonal and spatial distribution patterns across the Gulf of Mexico. The tags transmitted whenever the fin-mounted tags broke the sea surface, with orbiting satellites estimating shark positions based on these transmissions. Ajemian also analyzed overlap of core habitats among individuals relative to large benthic features including oil and gas platforms, natural banks, and bathymetric breaks."While all life stages of tiger sharks are known to occur in the Gulf of Mexico, detailed habitat use has never been quantified," said Ajemian. "This is rather striking as this marine system faces numerous humanmade stressors, complex tri-national management, and indications of size reductions in recreational landings for large sharks."Results showed significant ontogenetic and seasonal differences in distribution patterns as well as across-shelf (i.e., regional) and sex-linked variability in movement rates. Prior studies into tiger shark horizontal movements in the western North Atlantic Ocean have been restricted primarily to males or females separately, in disparate locations. By simultaneously tracking many males and females of varying life stages within the same region, the researchers observed sex and size-specific differences in distribution and movement rates, as well as associations with large-scale habitat features. For example, researchers found evidence of tiger shark core regions encompassing the National Oceanographic and Atmospheric Administration designated Habitat Areas of Particular Concern during cooler months, particularly by females. These are specifically bottom features of the Gulf that rise up from the edges of the continental shelf, and include places like the Flower Garden Banks National Marine Sanctuary. Additionally, shark core regions intersected with 2,504 oil and gas platforms, where previous researchers have observed them along the bottom.The scientists note that future research may benefit from combining alternative tracking tools, such as acoustic telemetry and genetic approaches, which can facilitate long-term assessment of tiger shark movement dynamics and help identify the role of the core habitats identified in this study."This research is just a first glimpse into how these iconic predators use the Gulf of Mexico's large marine ecosystem," said Ajemian.
|
Geography
| 2,020 |
July 15, 2020
|
https://www.sciencedaily.com/releases/2020/07/200715111443.htm
|
Data analytics can predict global warming trends, heat waves
|
New research from Arizona State and Stanford Universities is augmenting meteorological studies that predict global warming trends and heat waves, adding human originated factors into the equation.
|
The process quantifies the changing statistics of temperature evolution before global warming in the early 20th century and recent heat wave events to serve as the early warning signals for potential catastrophic changes. In addition, the study illustrates the contrast between urban and rural early warning signals for extreme heat waves.Tracking the pre-event signatures, or tipping points, of the increasing frequency and intensity of heat extremes will support the development of countermeasures to restore climate system resilience."Many studies have identified such changes in climate systems, like the sudden end of glacial period," said Chenghao Wang, a former ASU Research Scientist now at the Department of Earth System Science at Stanford University. "These qualitative changes usually have early-warning signals several thousand years before them.""We detected similar signals in events much shorter than previous studies," said Chenghao Wang. "We found early-warning signals also exist before global warming and heat waves on the time scale of years and days."In addition to global historical temperature data, the team tracks current temperature variances from airport weather stations. If it's abnormally hot, compared to 30 years of record, for at least three consecutive days, it's considered a heat wave."This method isn't just applicable for predicting extreme weather events in the next few days or weeks, said Zhihua Wang, an ASU environmental and water research engineering associate professor. "It observes human-induced variabilities and will support prediction over the next decades or even century." Zhihua Wang also serves as co-director of climate systems research at ASU's National Center of Excellence on Smart Materials for Urban Climate and Energy.The emergence of early-warning signals before heat waves provides new insights into the underlying mechanisms (e.g., possible feedback via land-atmosphere interactions). In particular, given the increasing frequency and intensity of heat extremes, the results will facilitate the design of countermeasures to reserve the tipping and restore the resilience of climate systems.According to Zhihua Wang, this method creates a "completely new frontier" for evaluating how things like global energy consumption and, conversely, the introduction of urban green infrastructure, are affecting climate change. "We're not replacing existing evaluation tools," he said. "The data is already there. It's enabling us to gauge what actions are having an impact."Based on the study results, researchers surmise that urban greening, or the use of public landscaping and forestry projects, along with adequate irrigation, may promote reverse tipping.In addition to Chenghao Wang and Zhihua Wang, the team included rising high school junior Linda Sun from Horace Greely High School in Chappaqua, NY.
|
Geography
| 2,020 |
July 15, 2020
|
https://www.sciencedaily.com/releases/2020/07/200715111431.htm
|
Monitoring groundwater changes more precisely
|
A new method could help to track groundwater changes better than before. To this end, researchers from Potsdam and Oberlin, Ohio (USA), have compared gravity field data from the GRACE and GRACE-Follow On satellite missions with other measuring methods. They investigated the seasonal water storage in almost 250 river basins in Asia, whose water regime is dominated by monsoon. The results allow the large-scale GRACE data to be scaled down to smaller regions. The researchers report on this in the journal
|
Knowledge of underground water storage is of existential importance for agriculture as well as for the drinking water supply in many regions. These reservoirs are replenished by precipitation and seeping water, which in turn feeds rivers and lakes and allows rivers to flow in dry seasons. Measurements, however, are difficult because it is difficult to look into the earth, so one has to rely on either point values only -- via boreholes and wells -- or on calculations from precipitation and runoff data.Since 2002 there has been another method of measuring groundwater changes: Via the GRACE satellite missions (from 2002 to 2017) and GRACE-Follow On (since 2018), the change in the amount of water in and on the earth can be determined on the basis of its gravity field signal. But this method also has its pitfalls. First, the mass changes measured by the GRACE-FO satellites say nothing about the depth in which the mass is located: Do lakes empty at the surface? Is the level of rivers falling? Or does water drain from deeper layers? Secondly, the GRACE-FO satellites provide data for comparatively large areas of several tens of thousands of square kilometres. It is currently not possible to resolve the gravity field data more precisely.In a new study, Amanda H. Schmidt from Oberlin College, Ohio, together with researchers from the German Research Centre for Geosciences, is showing how different methods can be cleverly combined to obtain reliable groundwater data even for small river basins. They have examined monsoon rainfall data and seasonal water storage in almost 250 river basins in Asia. The size of the individual areas varies from one thousand to one million square kilometres. The study covers almost all of Asia.The water balance on our planet is characterized by three main variables: precipitation, surface runoff and evaporation. The difference of these goes into or flows out of various reservoirs, e.g. the groundwater. Time series of measuring stations on rivers (hydrographs) after persistent precipitation show typical falling curves (so-called recession curves), which reflect the emptying of water reservoirs. Groundwater fluctuations can be estimated from these curves. Another method is the comparison of precipitation and runoff values by the time delay of the runoff; the temporary intermediate storage results in a so-called P-Q hysteresis. P stands for precipitation and Q for runoff. The area or size of the hysteresis loop can be used as a measure for the intermediate storage.The study in
|
Geography
| 2,020 |
July 15, 2020
|
https://www.sciencedaily.com/releases/2020/07/200715095448.htm
|
Renewable energy transition makes dollars and sense
|
Making the transition to a renewable energy future will have environmental and long-term economic benefits and is possible in terms of energy return on energy invested (EROI), UNSW Sydney researchers have found.
|
Their research, published in the international journal Honorary Associate Professor Mark Diesendorf, in collaboration with Prof Tommy Wiedmann of UNSW Engineering, analysed dozens of studies on renewable electricity systems in regions where wind and/or solar could provide most of the electricity generation in future, such as Australia and the United States.The Clean Energy Australia report states that renewable energy's contribution to Australia's total electricity generation is already at 24 per cent.Lead author A/Prof Diesendorf is a renewable energy researcher with expertise in electricity generation, while co-author Prof Tommy Wiedmann is a sustainability scientist.A/Prof Diesendorf said their findings were controversial in light of some fossil fuel and nuclear power supporters, as well as some economists, rejecting a transition to large-scale electricity renewables."These critics claim the world's economy would suffer because they argue renewables require too much lifecycle energy to build, to the point of diverting all that energy away from other uses," he said."Our paper shows that there is no credible scientific evidence to support such claims, many of which are founded upon a study published in 2014 that used data up to 30 years old."There were still research papers coming out in 2018 using the old data and that prompted me to examine the errors made by those perpetuating the misconception."A/Prof Diesendorf said critics' reliance on outdated figures was "ridiculous" for both solar and wind technology."It was very early days back then and those technologies have changed so dramatically just in the past 10 years, let alone the past three decades," he said."This evolution is reflected in their cost reductions: wind by about 30 per cent and solar by 85 to 90 per cent in the past decade. These cost reductions reflect increasing EROIs."A/Prof Diesendorf said fears about macro-economic damage from a transition to renewable energy had been exaggerated."Not only did these claims rely on outdated data, but they also failed to consider the energy efficiency advantages of transitioning away from fuel combustion and they also overestimated storage requirements," he said."I was unsurprised by our results, because I have been following the literature for several years and doubted the quality of the studies that supported the previous beliefs about low EROIs for wind and solar."A/Prof Diesendorf said the study focused on wind and solar renewables which could provide the vast majority of electricity, and indeed almost all energy, for many parts of the world in future."Wind and solar are the cheapest of all existing electricity generation technologies and are also widely available geographically," he said."We critically examined the case for large-scale electricity supply-demand systems in regions with high solar and/or high wind resources that could drive the transition to 100 per cent renewable electricity, either within these regions or where power could be economically transmitted to these regions."In these regions -- including Australia, the United States, Middle East, North Africa, China, parts of South America and northern Europe -- variable renewable energy (VRE) such as wind and/or solar can provide the major proportion of annual electricity generation."For storage, we considered hydroelectricity, including pumped hydro, batteries charged with excess wind and/or solar power, and concentrated solar thermal (CST) with thermal storage, which is a solar energy technology that uses sunlight to generate heat."Co-author Prof Wiedmann said the researchers used Net Energy Analysis as their conceptual framework within which to identify the strengths and weaknesses of past studies in determining the EROI of renewable energy technologies and systems."We used the established Net Energy Analysis method because it's highly relevant to the issue of EROI: it aims to calculate all energy inputs into making a technology in order to understand the full impact," Prof Wiedmann said."From mining the raw materials and minerals processing, to building and operating the technology, and then deconstructing it at the end of its life. So, it's a lifecycle assessment of all energy which humans use to make a technology."A/Prof Diesendorf said their findings revealed that a transition from fossil fuels to renewable energy was worthwhile, contradicting the assumptions and results of many previous studies on the EROIs of wind and solar."We found that the EROIs of wind and solar technologies are generally high and increasing; typically, solar at a good site could generate the lifecycle primary energy required to build itself in one to two years of operation, while large-scale wind does it in three to six months," he said."The impact of storage on EROI depends on the quantities and types of storage adopted and their operational strategies. In the regions we considered, the quantity of storage required to maintain generation reliability is relatively small."We also discovered that taking into account the low energy conversion efficiency of fossil-fuelled electricity greatly increases the relative EROIs of wind and solar."Finally, we found the macro-economic impact of a rapid transition to renewable electricity would at worst be temporary and would be unlikely to be major."A/Prof Diesendorf said he hoped the study's results would give renewed confidence to businesses and governments considering or already making a transition to more sustainable electricity technologies and systems."This could be supported by government policy, which is indeed the case in some parts of Australia -- including the ACT, Victoria and South Australia -- where there's strong support for the transition," he said."A number of mining companies in Australia are also going renewable, such as a steel producer which has a power purchase agreement with a solar farm to save money, while a zinc refinery built its own solar farm to supply cheaper electricity."A/Prof Diesendorf said the Australian Government, however, could help with more policies to smooth the transition to renewable energy."In Australia the transition is happening because renewable energy is much cheaper than fossil fuels, but there are many roadblocks and potholes in the way," he said."For example, wind and solar farms have inadequate transmission lines to feed power into cities and major industries, and we need more support for storage to better balance the variability of wind and solar."So, I hope our research will help bolster support to continuing with the transition, because we have discredited the claim that the EROIs of electricity renewables are so low that a transition could displace investment in other sectors."
|
Geography
| 2,020 |
July 14, 2020
|
https://www.sciencedaily.com/releases/2020/07/200714182228.htm
|
Global methane emissions soar to record high
|
Global emissions of methane have reached the highest levels on record. Increases are being driven primarily by growth of emissions from coal mining, oil and natural gas production, cattle and sheep ranching, and landfills.
|
Between 2000 and 2017, levels of the potent greenhouse gas barreled up toward pathways that climate models suggest will lead to 3-4 degrees Celsius of warming before the end of this century. This is a dangerous temperature threshold at which scientists warn that natural disasters, including wildfires, droughts and floods, and social disruptions such as famines and mass migrations become almost commonplace. The findings are outlined in two papers published July 14 in In 2017, the last year when complete global methane data are available, Earth's atmosphere absorbed nearly 600 million tons of the colorless, odorless gas that is 28 times more powerful than carbon dioxide at trapping heat over a 100-year span. More than half of all methane emissions now come from human activities. Annual methane emissions are up 9 percent, or 50 million tons per year, from the early 2000s, when methane concentrations in the atmosphere were relatively stable.In terms of warming potential, adding this much extra methane to the atmosphere since 2000 is akin to putting 350 million more cars on the world's roads or doubling the total emissions of Germany or France. "We still haven't turned the corner on methane," said Jackson, a professor of Earth system science in Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth).Globally, fossil fuel sources and cows are twin engines powering methane's upward climb. "Emissions from cattle and other ruminants are almost as large as those from the fossil fuel industry for methane," Jackson said. "People joke about burping cows without realizing how big the source really is."Throughout the study period, agriculture accounted for roughly two-thirds of all methane emissions related to human activities; fossil fuels contributed most of the remaining third. However, those two sources have contributed in roughly equal measure to the increases seen since the early 2000s.Methane emissions from agriculture rose to 227 million tons of methane in 2017, up nearly 11 percent from the 2000-2006 average. Methane from fossil fuel production and use reached 108 million tons in 2017, up nearly 15 percent from the earlier period.Amid the coronavirus pandemic, carbon emissions plummeted as manufacturing and transportation ground to a halt. "There's no chance that methane emissions dropped as much as carbon dioxide emissions because of the virus," Jackson said. "We're still heating our homes and buildings, and agriculture keeps growing."Methane emissions rose most sharply in Africa and the Middle East; China; and South Asia and Oceania, which includes Australia and many Pacific islands. Each of these three regions increased emissions by an estimated 10 to 15 million tons per year during the study period. The United States followed close behind, increasing methane emissions by 4.5 million tons, mostly due to more natural gas drilling, distribution and consumption."Natural gas use is rising quickly here in the U.S. and globally," Jackson said. "It's offsetting coal in the electricity sector and reducing carbon dioxide emissions, but increasing methane emissions in that sector." The U.S. and Canada are also producing more natural gas. "As a result, we're emitting more methane from oil and gas wells and leaky pipelines," said Jackson, who is also a senior fellow at Stanford's Woods Institute for the Environment and Precourt Institute for Energy.Europe stands out as the only region where methane emissions have decreased over the last two decades, in part by tamping down emissions from chemical manufacturing and growing food more efficiently. "Policies and better management have reduced emissions from landfills, manure and other sources here in Europe. People are also eating less beef and more poultry and fish," said Marielle Saunois of the Université de Versailles Saint-Quentin in France, lead author of the paper in Tropical and temperate regions have seen the biggest jump in methane emissions. Boreal and polar systems have played a lesser role. Despite fears that melting in the Arctic may unlock a burst of methane from thawing permafrost, the researchers found no evidence for increasing methane emissions in the Arctic -- at least through 2017.Human driven emissions are in many ways easier to pin down than those from natural sources. "We have a surprisingly difficult time identifying where methane is emitted in the tropics and elsewhere because of daily to seasonal changes in how waterlogged soils are," said Jackson, who also leads a group at Stanford working to map wetlands and waterlogged soils worldwide using satellites, flux towers and other tools.According to Jackson and colleagues, curbing methane emissions will require reducing fossil fuel use and controlling fugitive emissions such as leaks from pipelines and wells, as well as changes to the way we feed cattle, grow rice and eat. "We'll need to eat less meat and reduce emissions associated with cattle and rice farming," Jackson said, "and replace oil and natural gas in our cars and homes."Feed supplements such as algae may help to reduce methane burps from cows, and rice farming can transition away from permanent waterlogging that maximizes methane production in low-oxygen environments. Aircraft, drones and satellites show promise for monitoring methane from oil and gas wells. Jackson said, "I'm optimistic that, in the next five years, we'll make real progress in that area."Rob Jackson is Stanford's Michelle and Kevin Douglas Provostial Professor. Co-authors of the paper in The research received support from the Gordon and Betty Moore Foundation, Stanford University, the Australian Government's National Environmental Science Programme's Earth Systems and Climate Change Hub (JGC) and Future Earth.
|
Geography
| 2,020 |
July 14, 2020
|
https://www.sciencedaily.com/releases/2020/07/200714121748.htm
|
Evolution after Chicxulub asteroid impact: Rapid response of life to end-cretaceous mass
|
The impact event that formed the Chicxulub crater (Yucatán Peninsula, México) caused the extinction of 75% of species on Earth 66 million years ago, including non-avian dinosaurs. One place that did not experience much extinction was the deep, as organisms living in the abyss made it through the mass extinction event with just some changes to community structure.
|
New evidence from International Ocean Discovery Program (IODP) Expedition 364 of trace fossils of burrowing organisms that lived in the seafloor of the Chicxulub Crater beginning a few years after the impact shows just how quick the recovery of the seafloor ecosystem was, with the establishment of a well-developed tiered community within approximately 700,000 years after the event.In April and May 2016, a team of international scientists drilled into the Chicxulub impact crater. This joint expedition, organized by the International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) recovered an extended syn- and post-impact set of rock cores, allowing study of the effects of the impact on life and its recovery after the mass extinction event. The end Cretaceous (K-Pg) event has been profusely studied and its effect on biota are relatively well-known. However, the effect of these changes on the macrobenthic community, the community of organisms living on and in the seafloor that do not leave body fossils, is poorly known.The investigators concluded that the diversity and abundance of trace fossils responded primarily to variations in the flux of organic matter (i.e., food) sinking to the seafloor during the early Paleocene. Local and regional-scale effects of the K-Pg impact included earthquakes of magnitude 10-11, causing continental and marine landslides, tsunamis hundreds of meters in height that swept more than 300 km onshore, shock waves and air blasts, and the ignition of wildfires. Global phenomena included acid rain, injection of aerosols, dust, and soot into the atmosphere, brief intense cooling followed by slight warming, and destruction of the stratospheric ozone layer, followed by a longer-term greenhouse effect.Mass extinction events have punctuated the past 500 million years of Earth's history, and studying them helps geoscientists understand how organisms respond to stress in their environment and how ecosystems recover from the loss of biodiversity. Although the K-Pg mass extinction was caused by an asteroid impact, previous ones were caused by slower processes, like massive volcanism, which caused ocean acidification and deoxygenation and had environmental effects that lasted millions of years.By comparing the K-Pg record to earlier events like the end Permian mass extinction (the so-called "Great Dying" when 90% of life on Earth went extinct), geoscientists can determine how different environmental changes affect life. There are similar overall patterns of recovery after both events with distinct phases of stabilization and diversification, but with very different time frames. The initial recovery after the K-Pg, even at ground zero of the impact, lasted just a few years; this same phase lasted tens of thousands of years after the end Permian mass extinction. The overall recovery of seafloor burrowing organisms after the K-Pg took ~700,000 years, but it took several million years after the end Permian.
|
Geography
| 2,020 |
July 14, 2020
|
https://www.sciencedaily.com/releases/2020/07/200714102103.htm
|
29,000 years of Aboriginal history
|
The known timeline of the Aboriginal occupation of South Australia's Riverland region has been vastly extended by new research led by Flinders University in collaboration with the River Murray and Mallee Aboriginal Corporation (RMMAC).
|
Radiocarbon dating of shell middens -- remnants of meals eaten long ago -- capture a record of Aboriginal occupation that extends to around 29,000 years, confirming the location as one of the oldest sites along the 2500km river to become the oldest River Murray Indigenous site in South Australia.In the first comprehensive survey of the region, one of the oldest Indigenous sites along Australia's longest river system has been discovered. The results, published in "These results include the first pre-Last Glacial Maximum ages returned on the River Murray in South Australia and extend the known Aboriginal occupation of the Riverland by approximately 22,000 years," says Flinders University archaeologist and PhD candidate Craig Westell.More than 30 additional radiocarbon dates were collected in the region, spanning the period from 15,000 years ago to the recent present. Together, the results relate Aboriginal people to an ever-changing river landscape, and provide deeper insights into how they responded to these challenges.The period represented by the radiocarbon results brackets the Last Glacial Maximum (commonly known as the last Ice Age) when climatic conditions were colder and drier and when the arid zone extended over much of the Murray-Darling Basin. The river and lake systems of the basin were under stress during this time.In the Riverland, dunes were advancing into the Murray floodplains, river flows were unpredictable, and salt was accumulating in the valley.The ecological impacts witnessed during one of the worst droughts on record, the so-called Millennium Drought (from late 1996 extending to mid-2010), provides an idea of the challenges Aboriginal people may have faced along the river during the Last Glacial Maximum, and other periods of climate stress, researchers conclude."These studies show how our ancestors have lived over many thousands of years in the Riverland region and how they managed to survive during times of hardship and plenty," says RMMAC spokesperson Fiona Giles."This new research, published in Australian Archaeology, fills in a significant geographic gap in our understanding of the Aboriginal occupation chronologies for the Murray-Darling Basin," adds co-author Associate Professor Amy Roberts.The dating, which was undertaken at the Australian Nuclear Science and Technology Organisation (ANSTO) and Waikato University, forms part of a much larger and ongoing research program led by Associate Professor Amy Roberts which is undertaking a broad-ranging investigation of past and contemporary Aboriginal connections to the Riverland region.
|
Geography
| 2,020 |
July 13, 2020
|
https://www.sciencedaily.com/releases/2020/07/200713165600.htm
|
Burrowing crabs reshaping salt marshes, with climate change to blame
|
A new study reveals how climate change has enabled a voracious crab species to dramatically alter salt marsh ecosystems across the southeastern U.S.
|
The study, published in The clearing of grass by crabs has dramatically altered the flow of creeks that run through the marshes, the study found, and is altering the dynamics between predator and prey species in the marshes. In fact, the researchers say that Sesarma, which had previously been a minor player in southeastern salt marshes, can now be considered a keystone species, meaning it plays a dominant role in shaping the ecosystem."What we've found is an example of how sea level rise can activate a keystone species that's now dramatically remodeling these salt marshes," said Mark Bertness, a professor emeritus of ecology and evolutionary biology at Brown University and a coauthor of the research. "That's a big deal because sea level rise is a pervasive global phenomenon, and this is a largely unexpected consequence. We need to start thinking about how global climate change could activate new keystone species in other ecosystems."Research on Sesarma crabs and their impact on salt marshes has a long history in Bertness's lab at Brown. In 2011, Bertness and his students discovered that Sesarma, voracious grazers of cordgrass roots and leaves, were behind sudden die-offs of marshes on Cape Cod. In that case, overfishing had suddenly pulled predator species like striped bass out of the water, giving the crabs free reign to decimate the marshes. One of the undergraduate co-authors on that earlier research was Christini Angelini, now an associate professor at the University of Florida and a senior author on this new paper.Sesarma were known to inhabit southern marshes in Florida and the Carolinas, but their populations hadn't boomed like those further north. One potential reason for that was differing soil substrates. While working several years ago as an undergraduate researcher in Bertness' lab, Sinead Crotty, now project director at Yale's Carbon Containment Lab, showed that ground hardness played a big role in where Sesarma are able to establish themselves. Her findings indicated that Sesarma had a much easier time building burrows and feeding on grass roots in the peaty New England soil compared to harder soil substrates often found in southern marshes.But as sea levels continue to rise due to climate change, Crotty, Angelini and Bertness wondered if softening soils might be giving Sesarma more of a foothold in the South. Looking at aerial photos from nine locations across South Carolina and Florida, they found that the number of marsh creeks with evidence of Sesarma grazing increased by up to 240% from the late 1990s to the late 2010s. Meanwhile, surveys of sea level rise show that the ground in these areas is tidally submerged up to an hour longer per day now compared to the late 1990s."You've got the sea level rising, which softens the substrate that these crabs usually can't burrow in," Bertness said. "Now that it's softer you've got an ideal habitat to support these huge communal Sesarma burrows."This new Sesarma activity is reshaping marshes, the researchers found. Elimination of grasses has increased the rate at which creeks form in the marshes, and increases the drainage density of marsh creeks by up to 35%.Sesarma activity is also influencing interactions between predators and prey in the creeks. Clearing of grasses provides predators increased access to shellfish and other prey species. The research found that populations of mussels were dramatically lower in Sesarma-grazed creeks compared to creeks that weren't grazed."As they drown, southeastern U.S. marshes are fracturing from grasslands to patches of marsh, with depleted populations of mussels, snails and other invertebrates," Angelini said. "These dynamics reveal how quickly marshes may disappear with accelerating sea level rise and how long they will remain foraging grounds for commercially, recreationally and ecologically important species."The fact that Sesarma is now altering the geomorphology of the marshes, as well as the ecological interactions between other species, is evidence that it now qualifies as a keystone species in southern marshes. This is the first example, the researchers say, of activation of new keystone species as the result of anthropogenic climate change."This is going to be something for the textbooks," Bertness said. "This is an underappreciated way in which climate change alters ecosystems."The research was supported by the National Science Foundation (1652628, 1546638, 1315138).
|
Geography
| 2,020 |
July 13, 2020
|
https://www.sciencedaily.com/releases/2020/07/200713155002.htm
|
New models detail how major rivers will respond to changing environmental conditions
|
From the Nile to the Mississippi and from the Amazon to the Yangzi, human civilization is inextricably linked to the great rivers along which our societies developed. But rivers are mutable, and the benefits they bestow can quickly become disasters when these waterways change course.
|
Scientists are working to understand how environmental changes alter river dynamics. A new study in the Deltas counteract sea level rise by building up sediment, which mostly occurs near a river channel itself. Every once in a while, the river will switch course through an avulsion and begin building up the delta somewhere else. "So avulsions are the way that the river spreads its sediment out over the whole landscape," said first author Austin Chadwick, a postdoctoral scholar at University of Minnesota."The questions we're asking are how often do rivers naturally change their course," he continued, "and how is that going to change with climate change and human interference."Unfortunately, there has previously been no consensus on how rivers responded to climactic shift. Some scientists thought avulsion rates would increase as sea level rises, while others predicted they'd decrease. "There simply was no unifying theory to explain how river avulsion frequency is dependent on sea level," Ganti said.To straighten out the situation, Ganti, Chadwick and their coauthor Michael Lamb of Caltech, combined observations from the geologic and historical records with a mathematical model of river dynamics. By focusing on this specific issue, they aimed to finally get definitive answers and useful predictions.Large rivers tend to flatten out and decelerate as they approach the ocean. After a certain point, the downstream conditions of the sea level begin to influence the river's behavior in what scientists call backwater hydrodynamics. "This is a dynamic zone where deposition and erosion occurs in coastal rivers," Ganti explained.In a previous paper, the team had shown that avulsions occur within this backwater region, which can extend quite far inland. For instance, the backwater zone of the Mississippi River reaches 500 kilometers from the coast. Deeper, flatter rivers like the Mississippi, which have larger backwater regions, therefore have larger deltas.The researchers goal with this study was to apply their newfound understanding of the impact of backwater hydrodynamics to learn about the frequency of avulsions themselves.Using the model, and comparing their results to field data, the team discovered that there are three ways that deltas can respond to sea level rise, which depend on the balance between the rate of sea-level change and the sediment supplied by the river.The first: when a river has a lot of sediment and sea-level rise is relatively slow. According to the model, these rivers are resilient to sea-level rise, and their avulsion rates remain stable. China's Yellow River is one example.The second case occurs when a river has less sediment or the sea level rises more quickly. In this scenario, avulsions become more frequent. The rising ocean promotes sedimentation, and once a channel fills to a certain depth, the river will jump its course.And representing the extreme, in which sea level rise outpaces a river's ability to deposit sediment, is the third case. As the ocean infiltrates the delta, the river will reach its maximum avulsion rate, and the whole system will begin migrating inland. Scientists hadn't known about this case before, and the discovery of the three regimes together explains the previous inconsistencies in the scientific literature.The researchers inputted observations and data into their model to see whether various river deltas would behave differently under predicted climate conditions. "The answer is yes, for most of them," Chadwick said. "Many rivers will experience more frequent avulsions and some rivers will also have avulsions farther inland."River avulsions have huge societal implications, with the potential to cause economic and civil unrest. Archaeologists believe that a course change of the Indus River in western India directly contributed to the decline of the Bronze Age Harappan civilization. More recently, avulsions led to the 1877 Yellow River flood and 1931 China floods, two of the deadliest natural disasters in modern history.An avulsion could have dire consequences for rivers like the Mississippi, where a system called the Old River Control Structure has prevented the river from jumping course since 1963. If the backwater region migrated inland, the river could change course upstream from the facility and bypass it altogether. Millions of gallons of water per minute would course through previously dry land, while the downstream portion of the channel would go completely dry.The authors have made their model available and accessible to anyone who might want to use it. They were even able to reduce several formulas into a single equation by implementing a few basic assumptions about river conditions and dynamics."Groups like the Army Corps of Engineers and the Department of the Interior can use this tool to apply to any delta," said Chadwick. "And hopefully it will help inform our decisions in these places as we cope with climate change."
|
Geography
| 2,020 |
July 13, 2020
|
https://www.sciencedaily.com/releases/2020/07/200713104332.htm
|
Genetic differences between global American Crocodile populations identified in DNA analysis
|
A genetic analysis of the American crocodile (
|
The American crocodile is widespread across the American continent (from South Florida to Venezuela, across the Greater Antilles, and from Mexico to Ecuador). Successful due to its ability to thrive within brackish and saltwater environments. Efforts to conserve the crocodile species have existed since 1975 when their status was set to vulnerable on the IUCN (International Union for Conservation of Nature) red list. However, although conservation efforts have been put in place, the American crocodile faces further threats including habitat degradation due to coastal development.Replenishing these populations requires understanding of population structures through genetic analysis, which can elaborate on the evolution of the species' distribution. Gaining more understanding on how a species has come to be distributed so widely and how populations can differentiate genetically, can inform regions how best to manage their populations.The study reflected a regional collaborative effort, where DNA sampling occurred across seven countries including Venezuela, Jamaica and Cuba. There has been ongoing discussion on how these regional populations of C.acutus are similar. However, the study's results found that populations in Northern, Central and Southern America's and Great Antilles differed genetically. There were similarities found between Costa Rica and Jamaican populations. In Venezuela, they identified three new haplotypes, which are closely related genes that help scientists identify an origin of distribution.Researchers believe that the mating with different species could have contributed to this distribution, also known as hybridisation. Crocodiles hybridise easily, contributing to their ability to survive since the prehistoric era. Additionally, in Florida genetic analysis showed there had been a case of unintentional translocation, where the species had been moved from a different location over time. This had been flagged by previous research, where crocodiles with haplotypes from Central and South America had been transported to Florida, most likely for the pet trade, and later escaped or released into the wild by owners.By identifying these differences between regional populations of C. acutus, conservation efforts can establish population clusters which consider the populations as independent management units that may have different needs and focuses.Natalia Rossi, Country Manager of the Cuba Program at the Wildlife Conservation Society and the study's co-author explains some of the challenges around taking samples from large crocodiles: "Our study involved several research teams across multiple sites and countries and often in difficult field conditions. For four years between May to July the team would record, mark and sample crocodile hatchings, and juvenile and adult crocodiles in Cuba's Birama Swamp, one of the study sites. It was not unusual for us to have to spend hours in the mangrove lakes waiting for one to appear, and when a crocodile was spotted the whole team would have to enter the water to help net it. While both exciting and rewarding work, it is also dangerous as the crocodiles are powerful and it involves lots of team co-ordination and trust to secure the crocodile to enable us to take samples."The study was ambitious and could not have been achieved without its global collaboration and efforts from its long list of authors. In particular, the late John Thorbjarnarson and Rafael Crespo, who dedicated their lives to this research.
|
Geography
| 2,020 |
July 10, 2020
|
https://www.sciencedaily.com/releases/2020/07/200710140720.htm
|
Arctic Ocean changes driven by sub-Arctic seas
|
New research explores how lower-latitude oceans drive complex changes in the Arctic Ocean, pushing the region into a new reality distinct from the 20th-century norm.
|
The University of Alaska Fairbanks and Finnish Meteorological Institute led the international effort, which included researchers from six countries. The first of several related papers was published this month in Climate change is most pronounced in the Arctic. The Arctic Ocean, which covers less than 3% of the Earth's surface, appears to be quite sensitive to abnormal conditions in lower-latitude oceans."With this in mind, the goal of our research was to illustrate the part of Arctic climate change driven by anomalous [different from the norm] influxes of oceanic water from the Atlantic Ocean and the Pacific Ocean, a process which we refer to as borealization," said lead author Igor Polyakov, an oceanographer at UAF's International Arctic Research Center and FMI.Although the Arctic is often viewed as a single system that is impacted by climate change uniformly, the research stressed that the Arctic's Amerasian Basin (influenced by Pacific waters) and its Eurasian Basin (influenced by Atlantic waters) tend to differ in their responses to climate change.Since the first temperature and salinity measurements taken in the late 1800s, scientists have known that cold and relatively fresh water, which is lighter than salty water, floats at the surface of the Arctic Ocean. This fresh layer blocks the warmth of the deeper water from melting sea ice.In the Eurasian Basin, that is changing. Abnormal influx of warm, salty Atlantic water destabilizes the water column, making it more susceptible to mixing. The cool, fresh protective upper ocean layer is weakening and the ice is becoming vulnerable to heat from deeper in the ocean. As mixing and sea ice decay continues, the process accelerates. The ocean becomes more biologically productive as deeper, nutrient-rich water reaches the surface.By contrast, increased influx of warm, relatively fresh Pacific water and local processes like sea ice melt and accumulation of river water make the separation between the surface and deep layers more pronounced on the Amerasian side of the Arctic. As the pool of fresh water grows, it limits mixing and the movement of nutrients to the surface, potentially making the region less biologically productive.The study also explores how these physical changes impact other components of the Arctic system, including chemical composition and biological communities.Retreating sea ice allows more light to penetrate into the ocean. Changes in circulation patterns and water column structure control availability of nutrients. In some regions, organisms at the base of the food web are becoming more productive. Many marine organisms from sub-Arctic latitudes are moving north, in some cases replacing the local Arctic species."In many respects, the Arctic Ocean now looks like a new ocean," said Polyakov.These differences change our ability to predict weather, currents and the behavior of sea ice. There are major implications for Arctic residents, fisheries, tourism and navigation.This study focused on rather large-scale changes in the Arctic Ocean, and its findings do not necessarily represent conditions in nearshore waters where people live and hunt.The study stressed the importance of future scientific monitoring to understand how this new realm affects links between the ocean, ice and atmosphere.Co-authors of the paper include Matthew Alkire, Bodil Bluhm, Kristina Brown, Eddy Carmack, Melissa Chierici, Seth Danielson, Ingrid Ellingsen, Elizaveta Ershova, Katarina Gårdfeldt, Randi Ingvaldsen, Andrey V. Pnyushkov, Dag Slagstad and Paul Wassmann.
|
Geography
| 2,020 |
July 9, 2020
|
https://www.sciencedaily.com/releases/2020/07/200709210501.htm
|
Sea surface temperature has a big impact on coral outplant survival
|
Global average sea surface temperatures have risen at unprecedented rates for the past three decades, with far-reaching consequences for coral reefs. Today, the majority of coral reefs are surviving at their upper thermal limit and an increase in just one degree Celsius lasting longer than a few weeks can lead to coral bleaching and death. With projections of ocean warming expected to continue to rise by as much as 1.5 degrees Celsius in this century, scientists are in a race against time to find new solutions to sustain reefs.
|
One promising solution is "coral gardening" or outplanting, a method where coral fragments grown in a nursery are transplanted onto degraded reefs. Successful outplanting raises coral biomass and helps to restore reef function. Each year, thousands of corals are outplanted using this method.While effective, the technique is both time-consuming and expensive; the cost of reef restoration can reach $400,000 per hectare and success isn't always guaranteed. If the newly settled corals are exposed to stressors such as algae outbreaks, unfavorable water chemistry, and/or temperature fluctuations, they can quickly deteriorate and die. With temperature being one of the most fundamental factors determining coral health and survival, understanding its role in outplanting survival is crucial to restoration success.In a study published today in "Coral reefs experience a global, annual maximum sea surface temperature of about 29.4 degrees Celsius. Our study reveals that increasing the maximum temperature a site experiences by one degree higher reduces the chance of coral outplant survival to below 50%. We highlight the importance of considering temperatures a site has previously experienced to optimize outplant outcomes," said Shawna Foo, lead author and postdoctoral researcher at GDCS.The study was based on an analysis of hundreds of coral outplanting projects worldwide between 1987 and 2018. The team assessed data on coral survival rates, outplant locations and dates, along with sea surface temperature data extracted from satellites to determine the effects of temperature on outplant survival. They also considered whether temperatures from the year prior to coral outplanting showed similar patterns. The results of their analysis help to determine if a restoration site is appropriate or not."Although sobering for reef conservationists and managers, our findings provide a critical compass as to where reef restoration efforts can have their greatest impact in the future. Reef restoration is just now turning from a cottage industry to a global enterprise, and this needs to happen in concert with the changing global geography of ocean temperature," said Greg Asner, co-author of the study and director of GDCS.The study was supported by the John D. and Catherine T. MacArthur Foundation.
|
Geography
| 2,020 |
July 9, 2020
|
https://www.sciencedaily.com/releases/2020/07/200709141617.htm
|
Scientists urge caution, further assessment of ecological impacts above deep sea mining
|
Interest in deep-sea mining for copper, cobalt, zinc, manganese and other valuable metals has grown substantially in the last decade and mining activities are anticipated to begin soon. A new study, led by University of Hawai'i (UH) at Manoa researchers, argues that deep-sea mining poses significant risks, not only to the area immediately surrounding mining operations but also to the water hundreds to thousands of feet above the seafloor, threatening vast midwater ecosystems. Further, the scientists suggest how these risks could be evaluated more comprehensively to enable society and managers to decide if and how deep-sea mining should proceed.
|
Currently 30 exploration licenses cover about 580,000 square miles of the seafloor on the high seas and some countries are exploring exploitation in their own water as well. Most research assessing the impacts of mining and environmental baseline survey work has focused on the seafloor.However, large amounts of mud and dissolved chemicals are released during mining and large equipment produces extraordinary noise -- all of which travel high and wide. Unfortunately, there has been almost no study of the potential effects of mining beyond the habitat immediately adjacent to extraction activities."This is a call to all stakeholders and managers," said Jeffrey Drazen, lead author of the article and professor of oceanography at UH Manoa. "Mining is poised to move forward yet we lack scientific evidence to understand and manage the impacts on deep pelagic ecosystems, which constitute most of the biosphere. More research is needed very quickly."The deep midwaters of the world's ocean represent more than 90% of the biosphere, contain 100 times more fish than the annual global catch, connect surface and seafloor ecosystems, and play key roles in climate regulation and nutrient cycles. These ecosystem services, as well as untold biodiversity, could be negatively affected by mining.This recent paper, published in the "The current study shows that mining and its environmental impacts may not be confined to the seafloor thousands of feet below the surface but could threaten the waters above the seafloor, too," said Drazen. "Harm to midwater ecosystems could affect fisheries, release metals into food webs that could then enter our seafood supply, alter carbon sequestration to the deep ocean, and reduce biodiversity which is key to the healthy function of our surrounding oceans."In accordance with UN Convention on the Law of the Sea (UNCLOS), the International Seabed Authority (ISA) is required to ensure the effective protection of the marine environment, including deep midwater ecosystems, from harmful effects arising from mining-related activities. In order to minimize environmental harm, mining impacts on the midwater column must be considered in research plans and development of regulations before mining begins."We are urging researchers and governing bodies to expand midwater research efforts, and adopt precautionary management measures now in order to avoid harm to deep midwater ecosystems from seabed mining," said Drazen.
|
Geography
| 2,020 |
July 9, 2020
|
https://www.sciencedaily.com/releases/2020/07/200709141558.htm
|
A 'regime shift' is happening in the Arctic Ocean
|
Scientists at Stanford University have discovered a surprising shift in the Arctic Ocean. Exploding blooms of phytoplankton, the tiny algae at the base of a food web topped by whales and polar bears, have drastically altered the Arctic's ability to transform atmospheric carbon into living matter. Over the past decade, the surge has replaced sea ice loss as the biggest driver of changes in uptake of carbon dioxide by phytoplankton.
|
The research appears July 10 in The study centers on net primary production (NPP), a measure of how quickly plants and algae convert sunlight and carbon dioxide into sugars that other creatures can eat. "The rates are really important in terms of how much food there is for the rest of the ecosystem," Arrigo said. "It's also important because this is one of the main ways that COArrigo and colleagues found that NPP in the Arctic increased 57 percent between 1998 and 2018. That's an unprecedented jump in productivity for an entire ocean basin. More surprising is the discovery that while NPP increases were initially linked to retreating sea ice, productivity continued to climb even after melting slowed down around 2009. "The increase in NPP over the past decade is due almost exclusively to a recent increase in phytoplankton biomass," Arrigo said.Put another way, these microscopic algae were once metabolizing more carbon across the Arctic simply because they were gaining more open water over longer growing seasons, thanks to climate-driven changes in ice cover. Now, they are growing more concentrated, like a thickening algae soup."In a given volume of water, more phytoplankton were able to grow each year," said lead study author Kate Lewis, who worked on the research as a PhD student in Stanford's Department of Earth System Science. "This is the first time this has been reported in the Arctic Ocean."Phytoplankton require light and nutrients to grow. But the availability and intermingling of these ingredients throughout the water column depend on complex factors. As a result, although Arctic researchers have observed phytoplankton blooms going into overdrive in recent decades, they have debated how long the boom might last and how high it may climb.By assembling a massive new collection of ocean color measurements for the Arctic Ocean and building new algorithms to estimate phytoplankton concentrations from them, the Stanford team uncovered evidence that continued increases in production may no longer be as limited by scarce nutrients as once suspected. "It's still early days, but it looks like now there is a shift to greater nutrient supply," said Arrigo, the Donald and Donald M. Steel Professor in Earth Sciences.The researchers hypothesize that a new influx of nutrients is flowing in from other oceans and sweeping up from the Arctic's depths. "We knew the Arctic had increased production in the last few years, but it seemed possible the system was just recycling the same store of nutrients," Lewis said. "Our study shows that's not the case. Phytoplankton are absorbing more carbon year after year as new nutrients come into this ocean. That was unexpected, and it has big ecological impacts."The researchers were able to extract these insights from measures of the green plant pigment chlorophyll taken by satellite sensors and research cruises. But because of the unusual interplay of light, color and life in the Arctic, the work required new algorithms. "The Arctic Ocean is the most difficult place in the world to do satellite remote sensing," Arrigo explained. "Algorithms that work everywhere else in the world -- that look at the color of the ocean to judge how much phytoplankton are there -- do not work in the Arctic at all."The difficulty stems in part from a huge volume of incoming tea-colored river water, which carries dissolved organic matter that remote sensors mistake for chlorophyll. Additional complexity comes from the unusual ways in which phytoplankton have adapted to the Arctic's extremely low light. "When you use global satellite remote sensing algorithms in the Arctic Ocean, you end up with serious errors in your estimates," said Lewis.Yet these remote-sensing data are essential for understanding long-term trends across an ocean basin in one of the world's most extreme environments, where a single direct measurement of NPP may require 24 hours of round-the-clock work by a team of scientists aboard an icebreaker, Lewis said. She painstakingly curated sets of ocean color and NPP measurements, then used the compiled database to build algorithms tuned to the Arctic's unique conditions. Both the database and the algorithms are now available for public use.The work helps to illuminate how climate change will shape the Arctic Ocean's future productivity, food supply and capacity to absorb carbon. "There's going to be winners and losers," Arrigo said. "A more productive Arctic means more food for lots of animals. But many animals that have adapted to live in a polar environment are finding life more difficult as the ice retreats."Phytoplankton growth may also peak out of sync with the rest of the food web because ice is melting earlier in the year. Add to that the likelihood of more shipping traffic as Arctic waters open up, and the fact that the Arctic is simply too small to take much of a bite out of the world's greenhouse gas emissions. "It's taking in a lot more carbon than it used to take in," Arrigo said, "but it's not something we're going to be able to rely on to help us out of our climate problem."This research was supported by NASA's Earth and Space Science Fellowship program and the National Science Foundation.
|
Geography
| 2,020 |
July 9, 2020
|
https://www.sciencedaily.com/releases/2020/07/200709121240.htm
|
Two climate patterns predict coral bleaching months earlier
|
A new study by the Marine Laboratory at the University of Guam may help researchers predict coral bleaching months earlier than current tools, and, for the first time, may help predict invasion events of coral-eating crown-of-thorns starfish. The study was published on May 8 in
|
Coral bleaching and the crown-of-thorns starfish represent the two biggest disturbances coral reefs face, while local stressors like pollution and overfishing represent the two biggest impediments to recovery following disturbances.Unlike other prediction tools, this study used the interaction of two major oceanographic modulators -- El Niño and Pacific Decadal Oscillation, or PDO -- to predict how "warm blobs" of seawater and excess nutrients move around the tropical Western Pacific to cause these two destructive events. Existing tools typically provide bleaching warnings two to three weeks in advance; however, this new tool extends the warning period to between three and five months.Advanced warnings have important implications for coral reef management efforts in the Pacific region and potentially beyond."It takes management from a reactive position to a more proactive one," said senior author Peter Houk, an associate professor of marine biology in the Marine Lab. "Not a lot can be accomplished with only a couple weeks' notice, but predicting bleaching and starfish disturbance events a few months out may give governments and other agencies more time to acquire supplies, create legislation, and create support networks to ensure reefs are better equipped to handle these forces."For example, it allows more time to revise temporary fisheries regulations, raise funds for the removal of starfish, and procure supplies needed to support these acts. The authors have predicted outbreaks of starfish to emerge in Eastern Micronesia this year, providing time for Kosrae's tourism industry and resources agencies to gather supplies and build monitoring and removal plans now. Further, the authors can provide warnings for other islands down current to be on the lookout as starfish outbreaks are known to spread across islands and reefs in the direction of prevailing currents.Above-average sea-surface temperatures are common across the tropical Pacific following El Niño Southern Oscillation events, which are increasingly exacerbated by climate change. However, islands -- from Palau to Kosrae -- can be affected differently. One may bleach, while another experiences little to none.That question motivated researchers to study the impact of El Niño interacting with the PDO. Together, the two patterns predict maximum sea-surface temperatures and also the movement of "nutrient plumes" filled with what is known as "chlorophyll a" around the Pacific Ocean that attract plankton and cause the crown-of-thorns starfish outbreaks that wreak havoc on coral. Both sea-surface temperatures and nutrient plumes have been mapped by satellites for years; however, predicting their future has been a challenge.The researchers analyzed sea temperatures dating back to 1980 and biological data dating back to 1998, including coral cover and chlorophyll a plumes, from 82 survey sites on the main islands of Micronesia to track how they are influenced by the interaction of these two cycles.Using those observations, they built models that accurately predicted both sea surface temperatures and nutrients. The models accounted for 77% of the variation in sea temperature and 55% of the variation in chlorophyll a concentrations between 1980 to the present, both of which support strong predictions.The study shows that including PDO events into forecasts may improve predictions of when and where bleaching and starfish outbreaks will occur. The next step will be to build an online resource to host the predictive model for scientists and resources managers to access and to keep improving the model to the extent possible."We provide the first insight into how PDO and El Niño cycles predicted sea-surface temperatures, chlorophyll a concentrations, and changes to coral cover across the tropical north Pacific Ocean," the authors said. "These results may be transferrable to other oceanic regions to help predict coral reef status at even larger scales."
|
Geography
| 2,020 |
July 8, 2020
|
https://www.sciencedaily.com/releases/2020/07/200708121414.htm
|
Soil studies can be helpful for border control
|
Underground tunnels have been used by warriors and smugglers for thousands of years to infiltrate battlegrounds and cross borders. A new analysis published in the
|
"Understanding the history of soil tunnels shows us that certain types of soils and geographies are uniquely suited for tunneling. Countries with warfare or smuggling issues, including the U.S.-Mexico border and Israeli borders, need detailed soil and hydrology maps of their borders to identify soil types, typographies, and thus areas where soil tunnels could be constructed," according to study co-author Kenneth Olson, professor emeritus and soil scientist in the Department of Natural Resource and Environmental Sciences at the University of Illinois.Olson and co-author David Speidel looked at several tunnel systems throughout history, including examples in Syria, China, Cambodia, Vietnam, North Korea, South Korea, Iran, Iraq, Israel, Gaza, Egypt, Afghanistan, Mexico, and the United States.The authors discuss the history of each area's tunnels, including construction and use. They detail the geological materials, bedrock, water tables, and climate for each tunnel network, and note its resilience or demise.Using the case studies, the authors are able to identify site conditions that are most susceptible to soil tunneling and make specific recommendations for today's most vulnerable border crossings."Most cases of successful tunneling throughout history were in arid areas with a relatively low permanent water table," notes Olson. "These areas will need to be monitored for sound and vibrations to disrupt tunneling by smugglers."Olson's previous work explaining how soils and tunneling were an equalizer during the Vietnam War caught the eyes of several military groups, which led him to expand his soil tunnel warfare and smuggling research into this more recent study.Olson is a Vietnam-era veteran who served in the U.S. Army from 1969 to 1973. Speidel is a U.S. Army Iraq, Bosnia-Herzegovina, and Vietnam-era veteran as well as a USDA soil resource conservationist and retiree previously detailed by the Foreign Agricultural Service as a Civilian Response Crops Agricultural Advisor.
|
Geography
| 2,020 |
July 8, 2020
|
https://www.sciencedaily.com/releases/2020/07/200708110002.htm
|
The story behind a uniquely dark, wetland soil
|
When it comes to soils, proper identification is key. Identification allows scientists to determine the story behind the soil: how it formed, how it behaves in different scenarios, and how valuable it may be to certain plants and animals.
|
Soil classification, or scientific identification, can also help determine if the soil needs extra attention and resources for protection. For example, certain soils may not be safe for hiking, could be home to an endangered species, or foster a unique ecosystem like wetlands.However, soil classification is complex. Soil characteristics include color, texture, mineral composition, air and water content, and much more. Each of these characteristics can give added details to solve the story behind the soil.Many soils are simple for trained soil scientists to identify. But Karen Vaughan of the University of Wyoming and her team dug in to investigate an area of soil along the central coast of California that had some peculiar characteristics."The reason for this research site really comes from long ago in a wetlands field lab," she says. "Students kept saying the soil didn't meet all the field indicators of hydric -- or wetter -- soils. I thought, it has to. It's wet and there's plenty of water-loving vegetation. Then I realized it must be a problematic soil, so we set up this experiment to figure it out."Vaughan's experiment consisted of studying how dark the color of the soil was, as well as its water content, vegetation, and chemical composition. Looking at how wet the soils seemed, the vegetation that grew there, and microbes that lived there, a scientist would think they were wetland soils.However, other characteristics of the soil, such as its dark color, confused the researchers because it was so similar to the surrounding drier soil. This is where a way to analyze soil color more precisely, called the profile darkness index, was helpful. It allowed them to properly classify the soils.Soil classification is usually a pretty exact science. Hydric soils have a specific set of characteristics. One of the key characteristics of hydric soil is a pale, light greyish color. As a result of the uniquely dark color, they could be mistakenly identified as drier soils and not meet the requirements of wetlands.More clues for soil classification can sometimes be found in the landscape. Landslides are common on these cliffs, which cause soil to fall and be deposited in other areas. Often, these landslides result in depressions where a soil might be wetter than its surroundings."We get these situations where the soil characteristics don't match features we usually see in wetter soils," Vaughan explains. "This is, for example, because the transported soils inherited darker colors from the parent material. If someone looked at these soils, they would assume they are not as wet as they are. They then would not classify these areas as wetlands, despite them performing as wetlands.""This kind of proper identification is important so the wetlands can be better conserved," Vaughan says. "If researchers don't know about them, they can't be protected."This is because wetlands are so beneficial to the environment. They can help store water to protect against floods and erosion, as well as improve water quality. They also serve as a place for important plants and animals to live. Of course, they are also beautiful to observe when hiking out in nature."Soils tells the story of an ecosystem," she says. "If we look to the soil, we can understand ecosystem function."
|
Geography
| 2,020 |
July 8, 2020
|
https://www.sciencedaily.com/releases/2020/07/200708105912.htm
|
Tackling coral reefs' thorny problem: Crown-of-thorns starfish
|
Researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) have revealed the evolutionary history of the crown-of-thorns starfish -- a predator of coral that can devastate coral reefs. Their findings shed light on how the populations of these starfish have changed over time and could potentially help reduce their ecological destruction.
|
A single crown-of-thorns starfish is formidable, with a large body covered in spiky, venomous thorns. But their true danger lies in their potent reproductive ability, with female crown-of thorns starfish releasing millions of eggs in a single spawning. This can quickly lead to plagues, with uncontrollably large numbers of starfish rapidly destroying vast areas of coral reef."Almost 40 years ago, Okinawa experienced a massive outbreak of crown-of-thorns starfish, where over 1.5 million starfish had to be removed by divers by hand," said Professor Noriyuki Satoh, senior author of the student and leader of the Marine Genomics Unit at OIST.Although outbreaks have recently become less frequent around Okinawa and other subtropical islands in the Ryukyu Archipelago, they have become an increasingly large threat to the Great Barrier Reef in Australia, along with coral bleaching and tropical cyclones. These starfish outbreaks are becoming more common and more severe, as increasingly polluted and warmer waters aid the survival of the larvae.In 2017, the OIST Marine Genomics Unit teamed up with Australian scientists to decode the genome of the crown-of-thorns starfish, with their results published in Nature. Now, in their latest study published in The researchers collected crown-of-thorns starfish from coral reefs around three different islands in the Ryukyu Archipelago -- Okinawa, Miyako and Iriomote. The scientists then sequenced the entire DNA found in the mitochondria, comprised of over 16,000 nucleotide bases, and used differences in the sequences between the individual starfish to construct an evolutionary tree.The unit also performed the same analyses on two other starfish species -- the blue starfish and the northern Pacific sea star. By comparing the crown-of-thorns starfish to these other two species, the scientists hoped to see whether their findings revealed anything unique to the crown-of-thorns starfish."The blue starfish is also a coral reef predator that lives in the same habitat as the crown-of-thorns starfish, but it doesn't produce these uncontrollable outbreaks," said Prof. Satoh. "Meanwhile, the northern Pacific sea star is the most common starfish in Japan and lives in colder waters around the Japanese mainland."The scientists found that the evolutionary tree for the northern Pacific sea star showed that the species had split into two major lineages. Starfish collected from three different locations in the seas around the north-eastern regions of Japan were composed of individuals from one lineage, whilst a single population in the Seto Inland Sea in south-west Japan was formed of individuals from a second, more recent lineage."We believe that in a rare migration event, starfish larvae dispersed to the Seto Inland Sea. As these two areas are so separated, no migration occurred afterwards between the two populations, which resulted in the species splitting into two lineages," said Prof. Satoh. "Meanwhile, shorter range ocean currents kept individuals from the first lineage mixed between the nearby locations in the north-east of Japan."For the blue starfish, the results were more surprising. The constructed evolutionary tree showed that the species had first split into two lineages, with the second lineage then diverging again into two smaller subgroups. But intriguingly, individuals from the two major lineages were found in both Okinawa and Ishigaki -- the two areas in the Ryukyus where the blue starfish was collected. This means that two distinct starfish populations are living in the same geographic regions but are not breeding and mixing their genes. Prof. Satoh believes that this is strong evidence for there being two cryptic species of blue starfish -- in other words, the starfish look the same despite being separate, non-breeding species.The results also suggest that blue starfish migration occurs in both directions between Okinawa and Ishigaki. This was unexpected as the scientists had previously assumed that the powerful northeastern current flowing from Ishigaki towards Okinawa prevented starfish larvae from being carried in the opposite direction."For migration to readily occur in both directions, this suggests that the ocean currents in the Ryukyu Archipelago may be more complex that previously imagined," said Prof. Satoh.The results from the evolutionary tree of the crown-of-thorns starfish also supported the idea of complex ocean currents in the region, with each crown-of-thorns starfish lineage also found in more than one geographic location. This has important implications for predicting where new outbreaks of crown-of-thorns starfish may occur in the Ryukyus, with the researchers now advocating for better understanding of the ocean currents in the area.Overall, the evolutionary tree for the crown-of-thorns starfish looked significantly different from the other two starfish, underlying key differences in the species' historical population dynamics. Despite being a much younger species than the other two species, diverging less than one million years ago, the tree showed that the starfish quickly fragmented into five small lineages. These findings suggest that the species underwent frequent genetic bottlenecks, where the population was reduced to just a small number of individuals, which then jumpstarted a new lineage."This implies that the starfish outbreaks are just one part of a larger 'boom and bust' population cycle, where if they are left to their natural devices, the starfish eat so much coral that they run out of food and die," said Prof. Satoh.For their next steps, the Marine Genomics Unit is collaborating with Australian scientists to analyze crown-of-thorns starfish from the Great Barrier Reef. Instead of just using DNA in the mitochondria, the scientists aim to sequence the entire genome of each starfish, including DNA in the nucleus."Ultimately, we hope our findings can help us understand the population trends of the starfish better and the role of ocean currents in seeding new outbreaks," concluded Prof. Satoh. "This could potentially help us predict and therefore mitigate future outbreaks."
|
Geography
| 2,020 |
July 7, 2020
|
https://www.sciencedaily.com/releases/2020/07/200707113333.htm
|
1.5 billion people will depend on water from mountains
|
Global water consumption has increased almost fourfold in the past 100 years, and many regions can only meet their water demand thanks to essential contributions from mountain regions. In 30 years, almost a quarter of the world's lowland population will strongly depend on runoff from the mountains. Only sustainable development can ensure the important function of mountain areas as Earth's "water towers."
|
Water is a key resource for the 21st century, and many lowland regions all over the world depend on water resources originating in mountain regions, not least when it comes to irrigating agricultural land. A study led by the University of Zurich has now quantified this dependence for the first time by comparing water supply and consumption in the world's lowland areas with runoff contributions from the mountains. Based on a high-resolution global model, the study provides detailed information on the dependence on mountain water resources around the globe. The comprehensive analyses were carried out using a regular grid and then compared for every river catchment area of at least 10,000 km2. This allowed for highly differentiated insights into regional characteristics and differences."Until now, research has focused mainly on river basins that originate in High Mountain Asia," says Daniel Viviroli from the Department of Geography at the University of Zurich, first author of the study. "But in many other regions, irrigated agriculture is heavily dependent on water from mountainous areas, such as in the Middle East and North Africa, as well as parts of North America, South America and Australia."This dependence has increased strongly since the 1960s -- despite more efficient water use and thus declining per-capita water consumption. Whereas only 7 percent of the lowland population used to be strongly dependent on contributions from mountain areas at that time, this figure is projected to rise to 24 percent by mid-21st century. This corresponds to about 1.5 billion people in lowland areas. Particular focus is on catchment areas such as those of the Ganges-Brahmaputra-Meghna, Yangtze and Indus rivers in Asia, the Nile and Niger in Africa, the Euphrates and Tigris in the Middle East as well as the Colorado River in North America. For their analyses, the researchers assumed a middle-of-the-road scenario in terms of population growth as well as technological, economic and social development."Ensuring the function of mountains as 'water towers' should be a major concern of the world's lowland populations," says Viviroli. Sustainable development of mountain regions is therefore essential, for example by preventing agricultural overuse and ensuring the functioning of ecosystems, the researchers say. In addition, climate action is of paramount importance: Due to the rising temperatures, meltwater peaks from snow-covered mountain regions sometimes already occur several weeks earlier and are thus not as useful for summer agriculture. Adjustments in water management will be necessary, and possibly also new infrastructure such as dams and water transfers."However, technical solutions go hand in hand with major ecological damage, and some rivers, such as the Indus, have little potential for expansion," says Viviroli. For the future, it will be crucial that lowland and mountain regions work closely together despite political, cultural, social and economic differences.
|
Geography
| 2,020 |
July 7, 2020
|
https://www.sciencedaily.com/releases/2020/07/200707113248.htm
|
Climate change may cause extreme waves in Arctic
|
Extreme ocean surface waves with a devastating impact on coastal communities and infrastructure in the Arctic may become larger due to climate change, according to a new study.
|
The new research projects the annual maximum wave height will get up to two to three times higher than it is now along coastlines in areas of the Arctic such as along the Beaufort Sea. The new study in AGU's In addition, extreme wave events that used to occur once every 20 years might increase to occur once every two to five years on average, according to the study. In other words, the frequency of such extreme coastal flooding might increase by a factor of 4 to 10 by the end of this century."It increases the risk of flooding and erosion. It increases drastically almost everywhere," said Mercè Casas-Prat, a research scientist with Environment and Climate Change Canada's (ECCC) Climate Research Division and the lead author of the new study. "This can have a direct impact to the communities that live close to the shoreline."Earth's northernmost regions are a global warming hotspot, with some areas experiencing up to three times the warming of the rest of the world, Casas-Prat said. But researchers lack information on how the impacts may play out.Casas-Prat and her co-author Xiaolan Wang, also with the ECCC, wanted to examine how global warming might impact extreme ocean surface waves in the Arctic. Casas-Prat said some northern communities are already reporting accelerated erosion in some areas and increased building damage due to extreme waves. A worsening of these ocean conditions will have a direct impact on coastal communities, energy infrastructure, shipping, and even ecosystems and wildlife.Much of the Arctic is frozen for most of the year, but the warming climate is contributing to increasing periods of open water, which can become an issue when extreme waves are factored into the equation.In the new study, the scientists gathered five sets of multi-model simulations of oceanic and atmospheric conditions like surface winds, which generate waves, as well as sea ice for the RCP8.5 scenario, a future scenario commonly used in climate change projections that assumes low efforts to curb emissions. Then they ran simulations of wave conditions for two periods, from 1979 to 2005 (historical), then from 2081 to 2100 (future). Using the ensemble of multi-model simulations, they were able to assess the uncertainty in the changes in the extreme Arctic waves due to the uncertainty present in the five climate models used.One of their main findings was a projected notable wave height increase between these two periods in almost every place in the Arctic.Among the hardest-hit areas was in the Greenland Sea, which lies between Greenland and the Norwegian archipelago of Svalbard. The study found maximum annual wave heights there could increase by as much as 6 meters (19.7 feet).Casas-Prat said the models present a degree of uncertainty about how much waves heights might change, but she is confident there is going to be an increase. The researchers' predictions also showed that by the end of the century, the timing of the highest waves may also change."At the end of the century, the maximum will on average come later in the year and also be more extreme," Casas-Prat said.Judah Cohen, a climatologist at the Massachusetts Institute of Technology who was not involved in Casas-Prat's research, said these waves could be particularly devastating to coastal areas that have never previously experienced open water."The main conclusions of the paper are that waves will increase in height in the Arctic region and that Arctic coastlines are at greater risk to erosion and flooding are fairly straightforward," he said. "We are already seeing these increased risks along Arctic coastlines with damage to coastline structures that previously were never damaged."The researchers examined one area of coastline along the Beaufort Sea in northern Alaska and Canada, which holds a number of communities as well as energy infrastructure, and also found notable wave height increases there.Since larger waves can lead to increased risks of flooding and damage to coastal infrastructure, communities and development in this area might be affected by these waves. Flooding can also impact the availability of fresh water in some areas, as storm and wave surges can get into freshwater lagoons that communities rely on."As more and more ice melts and more of the Arctic ocean surface becomes exposed to the wind, waves will increase in height because wave height is dependent on the distance the wind blows over open waters," Cohen said.In another recent study published in AGU's journal Geophysical Research Letters, Casas-Prat and Wang examined the contribution of sea ice retreat on the projected increases in extreme wave heights in the Arctic. They found that surface winds alone cannot explain the changes in the regional maximum wave heights."Sea ice retreat plays an important role, not just by increasing the distance over which wind can blow and generate waves but also by increasing the chance of strong winds to occur over widening ice-free waters," Casas-Prat said.Increased waves could also increase the speed of ice breakup. The loss of ice due to waves could affect animals like polar bears which hunt seals on polar ice as well as a number of other creatures that rely on ice. It could also affect shipping routes in the future."Waves definitely have to be taken into account as an important factor to ensure those routes are safe," Casas-Prat said.
|
Geography
| 2,020 |
July 6, 2020
|
https://www.sciencedaily.com/releases/2020/07/200706152655.htm
|
First direct evidence of ocean mixing across the Gulf Stream
|
New research provides the first direct evidence for the Gulf Stream blender effect, identifying a new mechanism of mixing water across the swift-moving current. The results have important implications for weather, climate and fisheries because ocean mixing plays a critical role in these processes. The Gulf Stream is one of the largest drivers of climate and biological productivity from Florida to Newfoundland and along the western coast of Europe.
|
The multi-institutional study led by a University of Maryland researcher revealed that churning along the edges of the Gulf Stream across areas as small as a kilometer could be a leading source of ocean mixing between the waters on either side of the current. The study was published in the "This long-standing debate about whether the Gulf Stream acts as a blender or a barrier to ocean mixing has mainly considered big ocean eddies, tens of kilometers to a hundred kilometers across," said Jacob Wenegrat, an assistant professor in UMD's Department of Atmospheric and Oceanic Science and the lead author of the study. "What we're adding to this debate is this new evidence that variability at the kilometer scale seems to be doing a lot of mixing. And those scales are really hard to monitor and model."As the Gulf Stream courses its way up the east coast of the U.S. and Canada, it brings warm salty water from the tropics into the north Atlantic. But the current also creates an invisible wall of water that divides two distinct ocean regions: the colder, fresher waters along the northern edge of the Gulf Stream that swirl in a counterclockwise direction, and the warmer, saltier waters on the southern edge of the current that circulate in a clockwise direction.How much ocean mixing occurs across the Gulf Stream has been a matter of scientific debate. As a result, ocean models that predict climate, weather and biological productivity have not fully accounted for the contribution of mixing between the two very different types of water on either side of the current.To conduct the study, the researchers had to take their instruments to the source: the edge of the Gulf Stream. Two teams of scientists aboard two global-class research vessels braved winter storms on the Atlantic Ocean to release a fluorescent dye along the northern front of the Gulf Stream and trace its path over the following days.The first team released the dye along with a float containing an acoustic beacon. Downstream, the second team tracked the float and monitored the concentration of dye along with water temperature, salinity, chemistry and other features.Back on shore, Wenegrat and his coauthors developed high-resolution simulations of the physical processes that could cause the dye to disperse through the water in the manner the field teams recorded. Their results showed that turbulence across areas as small as a kilometer exerted an important influence on the dye's path and resulted in significant mixing of water properties such as salinity and temperature."These results emphasize the role of variability at very small scales that are currently hard to observe using standard methods, such as satellite observations," Wenegrat said. "Variability at this scale is not currently resolved in global climate models and won't be for decades to come, so it leads us to wonder, what have we been missing?"By showing that small-scale mixing across the Gulf Stream may have a significant impact, the new study reveals an important, under-recognized contributor to ocean circulation, biology and potentially climate.For example, the Gulf Stream plays an important role in what's known as the ocean biological pump -- a system that traps excess carbon dioxide, buffering the planet from global warming. In the surface waters of the Gulf Stream region, ocean mixing influences the growth of phytoplankton -- the base of the ocean food web. These phytoplankton absorb carbon dioxide near the surface and later sink to the bottom, taking carbon with them and trapping it in the deep ocean. Current models of the ocean biological pump don't account for the large effect small-scale mixing across the Gulf Stream could have on phytoplankton growth."To make progress on this we need to find ways to quantify these processes on a finer scale using theory, state-of-the-art numerical models and new observational techniques," Wenegrat said. "We need to be able to understand their impact on large-scale circulation and biogeochemistry of the ocean."
|
Geography
| 2,020 |
July 6, 2020
|
https://www.sciencedaily.com/releases/2020/07/200706094136.htm
|
Earth's magnetic field can change 10 times faster than previously thought
|
A new study by the University of Leeds and University of California at San Diego reveals that changes in the direction of the Earth's magnetic field may take place 10 times faster than previously thought.
|
Their study gives new insight into the swirling flow of iron 2800 kilometres below the planet's surface and how it has influenced the movement of the magnetic field during the past hundred thousand years.Our magnetic field is generated and maintained by a convective flow of molten metal that forms the Earth's outer core. Motion of the liquid iron creates the electric currents that power the field, which not only helps guide navigational systems but also helps shield us from harmful extra terrestrial radiation and hold our atmosphere in place.The magnetic field is constantly changing. Satellites now provide new means to measure and track its current shifts but the field existed long before the invention of human-made recording devices. To capture the evolution of the field back through geological time scientists analyse the magnetic fields recorded by sediments, lava flows and human-made artefacts. Accurately tracking the signal from Earth's core field is extremely challenging and so the rates of field change estimated by these types of analysis are still debated.Now, Dr Chris Davies, associate professor at Leeds and Professor Catherine Constable from the Scripps Institution of Oceanography, UC San Diego, in California have taken a different approach. They combined computer simulations of the field generation process with a recently published reconstruction of time variations in Earth's magnetic field spanning the last 100,000 yearsTheir study, published in They demonstrate that these rapid changes are associated with local weakening of the magnetic field. This means these changes have generally occurred around times when the field has reversed polarity or during geomagnetic excursions when the dipole axis -- corresponding to field lines that emerge from one magnetic pole and converge at the other -- moves far from the locations of the North and South geographic poles.The clearest example of this in their study is a sharp change in the geomagnetic field direction of roughly 2.5 degrees per year 39,000 years ago. This shift was associated with a locally weak field strength, in a confined spatial region just off the west coast of Central America, and followed the global Laschamp excursion -- a short reversal of the Earth's magnetic field roughly 41,000 years ago.Similar events are identified in computer simulations of the field which can reveal many more details of their physical origin than the limited paleomagnetic reconstruction.Their detailed analysis indicates that the fastest directional changes are associated with movement of reversed flux patches across the surface of the liquid core. These patches are more prevalent at lower latitudes, suggesting that future searches for rapid changes in direction should focus on these areas.Dr Davies, from the School of Earth and Environment, said: "We have very incomplete knowledge of our magnetic field prior to 400 years ago. Since these rapid changes represent some of the more extreme behaviour of the liquid core they could give important information about the behaviour of Earth's deep interior."Professor Constable said: "Understanding whether computer simulations of the magnetic field accurately reflect the physical behaviour of the geomagnetic field as inferred from geological records can be very challenging."But in this case we have been able to show excellent agreement in both the rates of change and general location of the most extreme events across a range of computer simulations. Further study of the evolving dynamics in these simulations offers a useful strategy for documenting how such rapid changes occur and whether they are also found during times of stable magnetic polarity like what we are experiencing today."
|
Geography
| 2,020 |
July 5, 2020
|
https://www.sciencedaily.com/releases/2020/07/200705185903.htm
|
MOSAiC floe: Sea ice formation
|
The New Siberian Islands were the birthplace of the MOSAiC floe: the sea ice in which the research vessel Polarstern is now drifting through the Arctic was formed off the coast of the archipelago, which separates the East Siberian Sea and the Laptev Sea to the north of Siberia, in December 2018. Sediments, and even small pebbles and bivalves, were incorporated into the ice during the freezing process, which the on-going melting process has brought to light on the surface of the MOSAiC floe. This is an increasingly rare phenomenon as nowadays most of the "dirty ice" melts before it even arrives in the Central Arctic. These are among the main findings of a study that MOSAiC experts have published now in the journal
|
At first glance, it looks like a group of people with dirty shoes had left tracks all over the snow. But in reality, they are sediments, and even small pebbles and bivalves, which the on-going melting process has brought to light on the surface of the MOSAiC floe. When the sea ice formed, they were frozen inside; accordingly, they hail from the nursery of sea ice along the Siberian Shelf, which the experts have now used a combination of model simulations and satellite data to describe in detail.The MOSAiC floe had already drifted over 1200 nautical miles in a meandering course when the research icebreaker Polarstern moored to it on 4 October 2019, at the coordinates 85° North and 137° East, and began to drift with it through the Arctic Ocean. While the current expedition team is busy taking readings in the Arctic, their colleagues back at home are analysing the data gathered. The precise analysis confirms the first impressions from the beginning of the expedition: "Our assessment shows that the entire region in which the two ships looked for suitable floes was characterised by unusually thin ice," reports Dr Thomas Krumpen, a sea-ice physicist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). Last autumn, the first author of "Our study shows that the floe we ultimately chose was formed in the shallow waters of the Russian shelf seas in December 2018," Krumpen explains. Off the coast of Siberia, strong offshore winds drive the young ice out to sea after it forms. In the shallow water, sediments are churned up from the seafloor and become trapped in the ice. Ice formation can also produce pressure ridges, the undersides of which sometimes scrape along the seafloor. As a result, stones can also become embedded in the sea ice. Now that the summertime melting has begun, all of this material is being revealed at the ice's surface: "At several points we've found entire mounds of pebbles measuring several centimetres in diameter, plus a number of bivalves," reports MOSAiC expedition leader Prof Markus Rex directly from the Arctic.Meanwhile, back home in Bremerhaven, Germany, Thomas Krumpen is thrilled to see that the now emerging 'bivalve ice with pebbles', as he has affectionately dubbed it, so clearly confirms the study's findings. The team of authors led by the AWI expert used a combination of satellite imagery, reanalysis data and a newly developed coupled thermodynamics backtracking model to reconstruct the floe's origins. Now Krumpen and his colleagues are devising a strategy for gathering samples of the sediments. The extent to which these 'dirty' and therefore darker patches accelerate melting on the floe is an important question, and answering it could enhance our understanding of the interactions between the ocean, ice and atmosphere, of biogeochemical cycles, and of life in the Arctic in general.In addition to mineral components, the sea ice also transports a range of other biogeochemical substances and gases from the coast to the central Arctic Ocean. They are an important aspect of MOSAiC research on biogeochemical cycles, i.e., on the formation or release of methane and other climate-relevant trace gases throughout the year. However, as a result of the substantial loss of sea ice observed in the Arctic over the past several years, precisely this ice, which comes from the shallow shelves and contains sediments and gases, is now melting more intensively in the summer, causing this material transport flow to break down. In the 1990s, the Polarstern was often in the same waters where the MOSAiC expedition began its drift. Back then the ice was still ca. 1.6 metres thick at the beginning of winter, whereas it had shrunk to ca. 50 centimetres last year -- which made the search for a sufficiently thick floe in the autumn of 2019 all the more difficult."We were fortunate enough to find a floe that had survived the summer and formed in the Russian shelf seas. This allows us to investigate transport processes from the 'old Arctic', which now only partly function, if at all," says Krumpen. Particularly in the higher latitudes, global warming is causing temperatures to climb rapidly: in the summer of 2019, the last summer before the expedition, Russian meteorological stations reported record temperatures. These high temperatures sparked rapid melting and significantly warmed Russia's marginal seas. As a result, many parts of the Northeast Passage were ice-free for a 93-day period (the longest duration since the beginning of satellite observation). The experts predict that if CO2 emissions remain unchecked -- as they have in the past several years -the Central Arctic could be ice-free in summer by 2030.
|
Geography
| 2,020 |
July 6, 2020
|
https://www.sciencedaily.com/releases/2020/07/200706114005.htm
|
Heatwave trends accelerate worldwide
|
The first comprehensive worldwide assessment of heatwaves down to regional levels has revealed that in nearly every part of the world heatwaves have been increasing in frequency and duration since the 1950s.
|
The research published in In Australia's worst heatwave season, an additional 80°C of cumulative heat was experienced across the country. In Russia and the Mediterranean, their most extreme seasons baked in an additional 200°C or more."Not only have we seen more and longer heatwaves worldwide over the past 70 years, but this trend has markedly accelerated," said lead author Dr Sarah Perkins Kirkpatrick from the ARC Centre of Excellence for Climate Extremes."Cumulative heat shows a similar acceleration, increasing globally on average by 1°C-4.5°C each decade but in some places, like the Middle East, and parts of Africa and South America, the trend is up to 10°C a decade."The only heatwave metric that hasn't seen an acceleration is heatwave intensity, which measures the average temperature across heatwaves. This is because globally we see more heatwave days and heatwaves are lasting longer. When the average temperature is measured across longer heatwaves any shifts in intensity are almost undetectable. Only southern Australia and small areas of Africa and South America show a detectable increase in average heatwave intensity.The study also identified that natural variability impacts on heatwaves can be large at regional levels. This variability can overwhelm heatwave trends, so regional trends shorter than a few decades are generally not reliable. To detect robust trend changes, the researchers looked at how the trends had changed over multi-decade intervals between 1950-2017. The changes were stark.For example, the Mediterranean, saw a dramatic uptick in heatwaves when measured over multi-decade spans. From 1950-2017, the Mediterranean saw an increase in heatwaves by two days a decade. But the trend from 1980 to 2017 had seen that accelerate to 6.4 days a decade.The regional approach also showed how the trends vary. Regions like the Amazon, north-east Brazil, west Asia and the Mediterranean are experiencing rapid changes in heatwaves while areas like South Australia and North Asia are still seeing changes but at a slower rate.However, no matter whether these changes are rapid or slow, it seems inevitable that vulnerable nations with less infrastructure will be hit hardest by extreme heat. "Climate scientists have long forecast that a clear sign of global warming would be seen with a change in heatwaves," said Dr Perkins Kirkpatrick."The dramatic region-by-region change in heatwaves we have witnessed over the past 70 years and the rapid increase in the number of these events, are unequivocal indicators that global warming is now with us and accelerating."This research is just the latest piece of evidence that should act as a clarion call to policymakers that urgent action is needed now if we are to prevent the worst outcomes of global warming. The time for inaction is over."
|
Geography
| 2,020 |
July 2, 2020
|
https://www.sciencedaily.com/releases/2020/07/200702144711.htm
|
Rising water temperatures could endanger the mating of many fish species
|
Because fish that are ready to mate and their young are especially sensitive to changes in temperature, in the future up to 60 percent of all species may be forced to leave their traditional spawning areas.
|
In a new meta-study, experts from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have published ground-breaking findings on the effects of climate change for fish stock around the globe. As they report, the risks for fish are much higher than previously assumed, especially given the fact that in certain developmental stages they are especially sensitive to rising water temperatures. One critical bottleneck in the lifecycle of fish is their low tolerance for heat during mating. In other words, the water temperature in their spawning areas determines to a great extent how successfully they reproduce, making fish particularly vulnerable to the impacts of climate change -- not only in the ocean, but also in lakes, ponds and rivers. According to the researchers' analyses, if left unchecked, climate change and rising water temperatures will negatively affect the reproduction of up to 60 percent of all fish species. Their study was released today in the latest issue of the journal Organisms have to breathe in order for their bodies to produce energy; this is equally true for human beings and for fish. In addition, we know that the energy needs of humans and animals alike depend on the temperature: when it's warmer, the need for energy rises exponentially, and with it, the need for oxygen. On this basis, it follows that organisms can only adapt to rising temperatures in their immediate vicinity by providing their bodies with more oxygen. But there are certain species-specific limits on this ability; if those limits are exceeded, it can lead to cardiovascular collapse.Armed with this knowledge, in a new meta-study, experts from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have investigated in which life phases saltwater and freshwater fish around the world are most sensitive to heat. To do so, the biologists compiled scientific data on the temperature tolerance of 694 fish species and analysed the temperature ranges within which fish can survive as adults ready to mate, as embryos in eggs, as larvae, and as adults outside the mating season."Our findings show that, both as embryos in eggs and as adults ready to mate, fish are far more sensitive to heat than in their larval stage or sexually mature adults outside the mating season," says first author and AWI marine biologist Dr Flemming Dahlke. "On the global average, for example, adults outside the mating season can survive in water that's up to 10 degrees Celsius warmer than adults ready to mate or fish eggs can."The reason for this variable temperature tolerance lies in the anatomy of fish: fish embryos have no gills that would allow them to take in more oxygen. In contrast, fish that are ready to mate produce egg and sperm cells; this additional body mass also needs to be supplied with oxygen, which is why, even at lower temperatures, their cardiovascular systems are under enormous strain.These findings apply to all fish species, and make it clear why fish are sensitive to heat, especially during the mating season and in their embryonic stage. Accordingly, in a second step the team of researchers analysed to what extent water temperatures in the spawning areas of the species investigated would likely rise due to climate change. For this purpose, they employed new climate scenarios (Shared Socioeconomic Pathways -- SSPs), which will also be used in the IPCC's next Assessment Report.Their conclusions confirm that every degree Celsius of warming spells more trouble for the world's fish stocks. "If we human beings can successfully limit climate warming to 1.5 degrees Celsius by the year 2100, only ten percent of the fish species we investigated will be forced to leave their traditional spawning areas due to rising temperatures," explains AWI biologist and co-author Prof Hans-Otto Pörtner. In contrast, if greenhouse-gas emissions remain at a high or very high level (SSP 5 -- 8.5), it's likely to produce average warming of 5 degrees Celsius or more, which would endanger up to 60 percent of all fish species.Those species affected would then be forced to either adapt through biological evolution -- a process that would most likely take far too long -- or to mate at another time of year or in some other place. "Some species might successfully manage this change," says Flemming Dahlke. "But if you consider the fact that fish have adapted their mating patterns to specific habitats over extremely long timeframes, and have tailored their mating cycles to specific ocean currents and available food sources, it has to be assumed that being forced to abandon their normal spawning areas will mean major problems for them." In addition, fish living in rivers and lakes have the problem that their habitat is limited by the size and geographic location of the waters they live in: migrating to deeper waters or to cooler regions is nearly impossible."Our detailed analyses, which cover all of the fishes' developmental stages, will help us to understand how these species are being affected by climate change, and to what extent the loss of suitable habitats is being driven by the climate-related transformation of ecosystems," says Hans-Otto Pörtner.Wherever fish migrate or their reproduction rates decline, there will be new interactions between species, and in some cases the ecosystems will experience a drop in productivity. The IPCC published corresponding projections on the future of worldwide fish stocks in its Special Report on the Ocean and Cryosphere in a Changing Climate. According to Pörtner: "Our new detailed assessments will help to improve those projections."
|
Geography
| 2,020 |
June 30, 2020
|
https://www.sciencedaily.com/releases/2020/06/200630193208.htm
|
Geologists identify deep-earth structures that may signal hidden metal lodes
|
If the world is to maintain a sustainable economy and fend off the worst effects of climate change, at least one industry will soon have to ramp up dramatically: the mining of metals needed to create a vast infrastructure for renewable power generation, storage, transmission and usage. The problem is, demand for such metals is likely to far outstrip currently both known deposits and the existing technology used to find more ore bodies.
|
Now, in a new study, scientists have discovered previously unrecognized structural lines 100 miles or more down in the earth that appear to signal the locations of giant deposits of copper, lead, zinc and other vital metals lying close enough to the surface to be mined, but too far down to be found using current exploration methods. The discovery could greatly narrow down search areas, and reduce the footprint of future mines, the authors say. The study appears this week in the journal "We can't get away from these metals-they're in everything, and we're not going to recycle everything that was ever made," said lead author Mark Hoggard, a postdoctoral researcher at Harvard University and Columbia University's Lamont-Doherty Earth Observatory. "There's a real need for alternative sources."The study found that 85 percent of all known base-metal deposits hosted in sediments-and 100 percent of all "giant" deposits (those holding more than 10 million tons of metal)-lie above deeply buried lines girdling the planet that mark the edges of ancient continents. Specifically, the deposits lie along boundaries where the earth's lithosphere-the rigid outermost cladding of the planet, comprising the crust and upper mantle-thins out to about 170 kilometers below the surface.Up to now, all such deposits have been found pretty much at the surface, and their locations have seemed to be somewhat random. Most discoveries have been made basically by geologists combing the ground and whacking at rocks with hammers. Geophysical exploration methods using gravity and other parameters to find buried ore bodies have entered in recent decades, but the results have been underwhelming. The new study presents geologists with a new, high-tech treasure map telling them where to look.Due to the demands of modern technology and the growth of populations and economies, the need for base metals in the next 25 years is projected to outpace all the base metals so far mined in human history. Copper is used in basically all electronics wiring, from cell phones to generators; lead for photovoltaic cells, high-voltage cables, batteries and super capacitors; and zinc for batteries, as well as fertilizers in regions where it is a limiting factor in soils, including much of China and India. Many base-metal mines also yield rarer needed elements, including cobalt, iridium and molybdenum. One recent study suggests that in order to develop a sustainable global economy, between 2015 and 2050 electric passenger vehicles must increase from 1.2 million to 1 billion; battery capacity from 0.5 gigawatt hours to 12,000; and photovoltaic capacity from 223 gigawatts to more than 7,000.The new study started in 2016 in Australia, where much of the world's lead, zinc and copper is mined. The government funded work to see whether mines in the northern part of the continent had anything in common. It built on the fact that in recent years, scientists around the world have been using seismic waves to map the highly variable depth of the lithosphere, which ranges down to 300 kilometers in the nuclei of the most ancient, undisturbed continental masses, and tapers to near zero under the younger rocks of the ocean floors. As continents have shifted, collided and rifted over many eons, their subsurfaces have developed scar-like lithospheric irregularities, many of which have now been mapped.The study's authors found that the richest Australian mines lay neatly along the line where thick, old lithosphere grades out to 170 kilometers as it approaches the coast. They then expanded their investigation to some 2,100 sediment-hosted mines across the world, and found an identical pattern. Some of the 170-kilometer boundaries lie near current coastlines, but many are nestled deep within the continents, having formed at various points in the distant past when the continents had different shapes. Some are up to 2 billion years old.The scientists' map shows such zones looping through all the continents, including areas in western Canada; the coasts of Australia, Greenland and Antarctica; the western, southeastern and Great Lakes regions of the United States; and much of the Amazon, northwest and southern Africa, northern India and central Asia. While some of the identified areas already host enormous mines, others are complete blanks on the mining map.The authors believe that the metal deposits formed when thick continental rocks stretched out and sagged to form a depression, like a wad of gum pulled apart. This thinned the lithosphere and allowed seawater to flood in. Over long periods, these watery low spots got filled in with metal-bearing sediments from adjoining, higher-elevation rocks. Salty water then circulated downward until reaching depths where chemical and temperature conditions were just right for metals picked up by the water in deep parts of the basin to precipitate out to form giant deposits, anywhere from 100 meters to 10 kilometers below the then-surface. The key ingredient was the depth of the lithosphere. Where it is thickest, little heat from the hot lower mantle rises to potential near-surface ore-forming zones, and where it is thinnest, a lot of heat gets through. The 170-kilometer boundary seems to be Goldilocks zone for creating just the right temperature conditions, as long as the right chemistry also is present."It really just hits the sweet spot," said Hoggard. "These deposits contain lots of metal bound up in high-grade ores, so once you find something like this, you only have to dig one hole." Most current base-metal mines are sprawling, destructive open-pit operations. But in many cases, deposits starting as far down as a kilometer could probably be mined economically, and these would "almost certainly be taken out via much less disruptive shafts," said Hoggard.The study promises to open exploration in so far poorly explored areas, including parts of Australia, central Asia and western Africa. Based on a preliminary report of the new study that the authors presented at an academic conference last year, a few companies appear to have already claimed ground in Australia and North America. But the mining industry is notoriously secretive, so it is not clear yet how widespread such activity might be."This is a truly profound finding and is the first time anyone has suggested that mineral deposits formed in sedimentary basins ... at depths of only kilometers in the crust were being controlled by forces at depths of hundreds of kilometers at the base of the lithosphere," said a report in Mining Journal reviewing the preliminary presentation last year.The study's other authors are Karol Czarnota of Geoscience Australia, who led the initial Australian mapping project; Fred Richards of Harvard University and Imperial College London; David Huston of Geoscience Australia; and A. Lynton Jaques and Sia Ghelichkhan of Australian National University.Hoggard has put the study into a global context on his website:
|
Geography
| 2,020 |
June 30, 2020
|
https://www.sciencedaily.com/releases/2020/06/200630111324.htm
|
Extreme warming of the South Pole
|
The South Pole has been warming at more than three times the global average over the past 30 years, according to research led by Ohio University professor Ryan Fogt and OHIO alumnus Kyle Clem.
|
Fogt, professor of meteorology and director of the Scalia Laboratory for Atmospheric Analysis, and Clem coauthored a paper with an international team of scientists published in the journal Clem, a current postdoctoral research fellow in climate science at Victoria University of Wellington in New Zealand, is the lead author of the study and studied under Fogt for both his bachelor's and master's degrees at Ohio University."I've had a passion for understanding the weather and fascination of its power and unpredictability as far back as I can remember," Clem said. "Working with Ryan I learned all about Antarctic and Southern Hemisphere climate, specifically how West Antarctica was warming and its ice sheet was thinning and contributing to global sea level rise. I also learned that Antarctica experiences some of the most extreme weather and variability on the planet, and due to its remote location we actually know very little about the continent, so there are constant surprises and new things to learn about Antarctica every year."The Antarctic climate exhibits some of the largest ranges in temperature during the course of the year, and some of the largest temperature trends on the planet, with strong regional contrasts. Most of West Antarctica and the Antarctic Peninsula experienced warming and ice-sheet thinning during the late 20th century. By contrast, the South Pole -- located in the remote and high-altitude continental interior -- cooled until the 1980s and has since warmed substantially. These trends are affected by natural and anthropogenic climate change, but the individual contribution of each factor is not well understood.Clem and his team analyzed weather station data at the South Pole, as well as climate models to examine the warming in the Antarctic interior. They found that between 1989 and 2018, the South Pole had warmed by about 1.8 degrees Celsius over the past 30 years at a rate of +0.6 degrees Celcius per decade -- three times the global average.The study also found that the strong warming over the Antarctic interior in the last 30 years was mainly driven by the tropics, especially warm ocean temperatures in the western tropical Pacific Ocean that changed the winds in the South Atlantic near Antarctica and increased the delivery of warm air to the South Pole. They suggest these atmospheric changes along Antarctica's coast are an important mechanism driving climate anomalies in its interior.Clem and Fogt argue that these warming trends were unlikely the result of natural climate change alone, emphasizing the effects of added anthropogenic warming on top of the large tropical climate signal on Antarctic climate have worked in tandem to make this one of the strongest warming trends worldwide."From the very beginning, Kyle and I worked very well together and were able to accomplish more as a team than we were individually," Fogt said. "We have published every year together since 2013, with one of our continuing collaborations being the annual State of the Climate reports. Our work on this project together each year ultimately led to this publication documenting the warming at the South Pole, however, most importantly for me, apart from being a fantastic scientist and collaborator, my family and I are both honored to consider Kyle one of our closest friends."
|
Geography
| 2,020 |
June 30, 2020
|
https://www.sciencedaily.com/releases/2020/06/200630103603.htm
|
Plastic recycling from Europe is being dumped in Asian waters
|
New research from NUI Galway and the University of Limerick has for the first time quantified the volume of plastic from European countries (EU, UK, Switzerland and Norway) that contributes to ocean littering from exported recycling.
|
While European countries have developed world-leading waste management infrastructure, 46% of European separated plastic waste is exported outside the country of origin. A large share of this plastic is transported thousands of kilometres to countries with poor waste management practices, largely located in Southeast Asia. Once in these countries, a large share of the waste is rejected from recycling streams into overstretched local waste management systems that have been found to contribute significantly to ocean littering.This new research, published in the scientific journal Speaking today, George Bishop, lead author of the study said: "The results indicate an important and previously undocumented pathway of plastic debris entering the oceans, which will have considerable environmental and social impacts on marine ecosystems and coastal communities."Using detailed international trade data and data on waste management in destination countries, the study modelled the fate of all polyethylene exported for recycling from Europe, accounting for different fates ranging from successful conversion into recycled resins, or ending up as landfill, incineration, or ocean debris.Dr David Styles, a lecturer at the University of Limerick and co-author, explains, "Given that such a large share of waste destined for recycling is exported, with poor downstream traceability, this study suggests that 'true' recycling rates may deviate significantly from rates reported by municipalities and countries where the waste originates. In fact, our study found that up to 31% of the exported plastic wasn't actually recycled at all."The study was part of the Science Foundation Ireland funded, 'Innovative Energy Technologies for Bioenergy, Biofuels and a Sustainable Irish Bioeconomy: IETSBIO3' led by Professor Piet Lens, Established Professor of New Energy Technologies at the National University of Ireland, Galway.Professor Lens added: "To successfully move towards a more circular economy, European municipalities and waste management companies need to be held accountable for the final fate of "recycled" waste. Our study highlights the lack of available data on plastic waste and the need to consider extended audit trails, or "on-shoring" of recycling activities as part of emerging regulations around trade in plastic waste."The authors caution that these findings should not discourage people to recycle as it remains the best waste management treatment, environmentally speaking. However, there is considerable work to be done to improve aspects of these plastic recycling chains, to reduce the 'leakage' of these systems.
|
Geography
| 2,020 |
June 30, 2020
|
https://www.sciencedaily.com/releases/2020/06/200630072044.htm
|
Major new paleoclimatology study shows global warming has upended 6,500 years of cooling
|
Over the past 150 years, global warming has more than undone the global cooling that occurred over the past six millennia, according to a major study published June 30 in Nature Research's
|
Four researchers of Northern Arizona University's School of Earth and Sustainability (SES) led the study, with Regents' professor Darrell Kaufman as lead author and associate professor Nicholas McKay as co-author, along with assistant research professors Cody Routson and Michael Erb. The team worked in collaboration with scientists from research institutions all over the world to reconstruct the global average temperature over the Holocene Epoch -- the period following the Ice Age and beginning about 12,000 years ago."Before global warming, there was global cooling," said Kaufman. "Previous work has shown convincingly that the world naturally and slowly cooled for at least 1,000 years prior to the middle of the 19th century, when the global average temperature reversed course along with the build-up of greenhouse gases. This study, based on a major new compilation of previously published paleoclimate data, combined with new statistical analyses, shows more confidently than ever that the millennial-scale global cooling began approximately 6,500 years ago."Earlier this year, an international group of 93 paleoclimate scientists from 23 countries -- also led by Kaufman, McKay, Routson and Erb -- published the most comprehensive set of paleoclimate data ever compiled for the past 12,000 years, compressing 1,319 data records based on samples taken from 679 sites globally. At each site, researchers analyzed ecological, geochemical and biophysical evidence from both marine and terrestrial archives, such as lake deposits, marine sediments, peat and glacier ice, to infer past temperature changes. Countless scientists working around the world over many decades conducted the basic research contributing to the global database."The rate of cooling that followed the peak warmth was subtle, only around 0.1°C per 1,000 years. This cooling seems to be driven by slow cycles in the Earth's orbit, which reduced the amount of summer sunlight in the Northern Hemisphere, culminating in the 'Little Ice Age' of recent centuries," said Erb, who analyzed the temperature reconstructions.Since the mid-19th century, global warming has climbed to about 1°C, suggesting that the global average temperature of the last decade (2010-2019) was warmer than anytime during the present post-glacial period.McKay, who developed some of the statistical approaches to synthesizing data from around the world, notes that individual decades are not resolved in the 12,000-year-long temperature reconstruction, making it difficult to compare it with any recent decade. "On the other hand, this past decade was likely cooler than what the average temperatures will be for the rest of this century and beyond, which are very likely to continue to exceed 1°C above pre-industrial temperatures," McKay said."It's possible," Kaufman said, "that the last time the sustained average global temperature was 1°C above the 19th century was prior to the last Ice Age, back around 125,000 years ago when sea level was around 20 feet higher than today.""Investigating the patterns of natural temperature changes over space and time helps us understand and quantify the processes that cause climate to change, which is important as we prepare for the full range of future climate changes due to both human and natural causes," said Routson. He used an earlier version of the database to link Arctic warming to a reduction in precipitation at mid latitudes (see related article)."Our future climate will largely depend on the influence of human factors, especially the build-up of greenhouse gases. However, future climate will also be influenced by natural factors, and it will be complicated by the natural variability within the climate system. Future projections of climate change will be improved by better accounting for both anthropogenic and natural factors," he said.The reconstruction of past global temperature is the outgrowth of several NAU research projects aimed at understanding the causes and effects of natural climate variability, work that was funded through more than $1.2 million in grants from the National Science Foundation. The team was recently awarded another $678,000 in grants from the NSF for related work extending through 2023.
|
Geography
| 2,020 |
June 30, 2020
|
https://www.sciencedaily.com/releases/2020/06/200626114819.htm
|
Native bees' exotic origins reveal cross-pollination
|
Ancestors of a distinctive pollinating bee found across Australia probably originated in tropical Asian countries, islands in the south-west Pacific or greater Oceania region, ecology researchers claim.
|
Describing the likely dispersal corridor for the ancestral lineage of the bee genus Homalictus will help understand the social evolution of the vibrant halictine bees, South Australian, Czech and PNG researchers say in a new paper.It follows earlier research connecting the origin of other Australian bees to the polar south or Antarctica routes millions of years ago -- helping to explain the diversity and complexity of natural ecosystems and their resilience or susceptibility during periods of climate change.Ecologists are hopeful that the diverse origins of native bees are giving them an edge in withstanding and adapting further to climate change."Homalictus bees are a leading generalist plant pollinator across Australia and as far north as southern China," says Flinders University PhD candidate, photographer and native bee expert James Dorey."Our study highlights the importance of the habitat and ecology of tropical regions, including Papua New Guinea and the Fijian islands, for our endemic species and shows us how these bees might have expanded across the Pacific and possibly higher latitudes of Southeast Asia."SA Museum senior researcher Associate Professor Mark Stevens says the ongoing research aims to better understand the origin and radiation of insects and other animals, help environmental management during changing climates and mitigate the effects of further human expansion and habitat destruction."Many species historically evolved under difference climatic conditions and those different histories may determine how they will cope with new climates," he says."As climates change, species that have narrow thermal tolerances that are unable to adapt either track their preferred climate by moving, or become extinct. We see this in our studies on tropical bees and also in the studies of Antarctic biodiversity.""What has not been fully appreciated is the movement of bees in the southern hemisphere that included Antarctica as a likely dispersal corridor before it became the glacial continent that it is today."Antarctica was the crossroads between South America, Africa and Australia as the supercontinent of Gondwana was breaking up. The last landmass connections between Australia and Antarctica finished about 35 million years ago while the interchange with Asia began about 20 million years ago.In contrast to the colourful tropical varieties, SA researchers have previously explored the origins of the cooler adapted and less colourful Exoneurine allodapine bees, believed to have originated in Africa but dispersed to Australia about 42-34 million years ago from Antarctica when there was still a land bridge connection to Tasmania.Co-author on the online Homalictus paper, Associate Professor Mike Schwarz says Australia has the most unusual bee fauna in the world, resulting from three major events -- the gradual breakup of Gondwana, then a period when the bees evolved in "splendid isolation," long before humans arrived."Thirdly, there was a northern influx of species from tropical Asia as the Australian continent collided with Asia. "Australia's complex systems diversity if a key ingredient for survival of our species," Flinders Associate Professor Schwarz says."Hopefully, the diversity of our native bees will make them more resilient to future climate scenarios, which will be critical for agriculture in a changing world.
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629202009.htm
|
Beavers gnawing away at the permafrost
|
Alaska's beavers are profiting from climate change, and spreading rapidly. In just a few years' time, they have not only expanded into many tundra regions where they'd never been seen before; they're also building more and more dams in their new homes, creating a host of new water bodies. This could accelerate the thawing of the permafrost soils, and therefore intensify climate change, as an International American-German research team reports in the journal
|
When it comes to completely transforming a landscape, beavers are hard to beat. Very few other animals are capable of changing their habitat as precisely as these brown-furred rodents, which can weigh up to 30 kilograms. Armed with sharp teeth, they fell trees and shrubs and build dams, causing small valleys to fill with water and forming new lakes, which can easily measure a few hectares. "Their methods are extremely effective," says Dr Ingmar Nitze from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Potsdam/Germany. They often build their dams at precisely those points where they can achieve major effects with minimal effort.This is something that Ingmar Nitze has repeatedly seen in the Arctic regions of Alaska, where the North American beaver is active. The researcher is an expert on remote sensing, and is especially interested in those parts of the Earth where the soil is permanently frozen. Climate researchers fear that, as temperatures rise, this permafrost could increasingly thaw and become unstable. If that happens, it could release massive quantities of greenhouse gases, which would intensify climate change.Accordingly, Nitze and his colleagues are monitoring the development of these landscapes with the aid of satellite images. One interesting aspect in this regard: how the lakes and other bodies of water are distributed. Because the water they contain is somewhat warmer than the surrounding soil, these lakes and ponds can further accelerate permafrost thawing. And beavers would seem to be actively contributing to the process.Back in 2018, Ingmar Nitze and Guido Grosse from the AWI, together with colleagues from the USA, determined that the beavers living in an 18,000-square-kilometre section of northwest Alaska had created 56 new lakes in just five years. For their new study, the team from the AWI, the University of Alaska in Fairbanks, and the University of Minnesota in Minneapolis have now taken a closer look at this trend. Using detailed satellite data and extended time series, the experts tracked the beavers' activities in two other regions in Alaska -- and were surprised by what they found."Of course, we knew that the beavers there had spread substantially over the last few decades," says Nitze. This is partly due to climate change; thanks to rising temperatures, now more and more habitats offer the shrubs that the animals need for food and building material. Furthermore, the lakes, which used to freeze solid, now offer beaver-friendlier conditions, thanks to their thinner seasonal winter ice cover. Lastly, the rodents aren't hunted as intensively as in the past. As a result, it's a good time to be a beaver in the Arctic."But we never would have dreamed they would seize the opportunity so intensively," says Nitze. The high-resolution satellite images of the roughly 100-square-kilometre study area near the town of Kotzebue reveal the scale of the animals' activities there. From just two dams in 2002, the number had risen to 98 by 2019 -- a 5,000-percent increase, with more than 5 new dams being constructed per year. And the larger area surveyed, which covers the entire northern Baldwin Peninsula, also experienced a beaver dam boom. According to Nitze, "We're seeing exponential growth there. The number of these structures doubles roughly every four years."This has already affected the water balance. Apparently, the rodents intentionally do their work in those parts of the landscape that they can most easily flood. To do so, sometimes they dam up small streams, and sometimes the outlets of existing lakes, which expand as a result. "But they especially prefer drained lake basins," Benjamin Jones, lead author of the study, and Nitze report. In many cases, the bottoms of these former lakes are prime locations for beaver activity. "The animals have intuitively found that damming the outlet drainage channels at the sites of former lakes is an efficient way to create habitat. So a new lake is formed which degrades ice-rich permafrost in the basin, adding to the effect of increasing the depth of the engineered waterbody," added Jones. These actions have their consequences: in the course of the 17-year timeframe studied, the overall water area in the Kotzebue region grew by 8.3 percent. And roughly two-thirds of that growth was due to the beavers.The researchers suspect that there have been similar construction booms in other regions of the Arctic; accordingly, they now want to expand their 'beaver manhunt' across the Arctic. "The growth in Canada, for example, is most likely even more extreme," says Nitze. And each additional lake thaws the permafrost below it and on its banks. Granted, the frozen soil could theoretically bounce back after a few years, when the beaver dams break; but whether or not the conditions will be sufficiently cold for that to happen is anyone's guess. For Ingmar Nitze, all of these aspects mean there are plenty of reasons to keep an eye on these four-legged landscape engineers: "Anyone who wants to predict the future of the permafrost should be sure to keep the beaver in mind."
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629124059.htm
|
Global ripple effect of shifting monsoons
|
Scientists from the Department of Energy's Oak Ridge National Laboratory and a dozen other international research institutions have produced the most elaborate set of projections to date that illustrates possible futures for major monsoon regions.
|
Multiple regions around the world plan energy production, agricultural practices and other essential economic endeavors based on the annual arrival of monsoons, which entails a seasonal shift in the direction of winds that provides periods of steady rainfall. However, unchecked greenhouse gas emissions could disrupt these traditionally predictable events.Using RegCM4, the latest version of a popular regional climate model developed by the International Centre for Theoretical Physics in Italy, the team ran a series of simulations to project and evaluate changes in nine monsoon regions across five continents. The researchers designed the simulations with a tight grid of each region containing spacing of less than 16 miles, which provided a substantial level of detail.The team, part of a global effort called the Coordinated Regional Downscaling Experiment, or CORDEX, published its findings in "This is the first time that a regional climate model has been used to provide a global view of changes in monsoons," said lead author Moetasim Ashfaq, a climate computational scientist at ORNL. "It took a great deal of time and effort to compile and analyze such high-profile, high-resolution data, and these detailed simulations would not have been possible without a significant international collaboration."ORNL researchers simulated the South Asian monsoon region using resources of the laboratory's Compute and Data Environment for Science and the compute cluster Eos, and the rest of the simulations were conducted at various other computing centers. The team uncovered commonalities in regional monsoon responses to increases in greenhouse gas emissions. These responses included monsoon onset delays, shorter monsoon seasons and more intense seasonal fluctuation.The simulations predicted and compared changes that would occur in different scenarios provided by the Intergovernmental Panel on Climate Change, or IPCC, known as Representation Concentration Pathway, or RCP8.5 and RCP2.6.RCP8.5 assumes that carbon emissions follow a "business as usual" scenario without policy interventions, whereas RCP2.6 is based on much lower increases in emissions with aggressive mitigation policies. Although the monsoon patterns will likely change for both RCPs, the simulations revealed that the amount of change would likely be minimal under RCP2.6 but could be significant under RCP8.5."If emissions are reduced based on RCP2.6 out to the year 2100, the simulations show that the long, damaging shifts in monsoon behaviors can mostly be avoided," Ashfaq said. "If you look at the best-case scenario, we do still see changes, but they are insignificantly different from the typical year-to-year variation in regional monsoons that communities are already accustomed to."Seven of the nine monsoon regions showed a gradual delay in monsoon onset with a continuous increase in global emissions, which could create wide-ranging consequences that directly affect approximately two-thirds of the world's population by the end of this century. Unlike the areas that receive relatively even amounts of precipitation in all seasons, heavily populated monsoon regions receive 60% to 70% of their precipitation during the summer monsoon season."The RCP8.5 simulations reveal robust delays in the start of rainy seasons that ripple through many aspects of everyday life in these regions," Ashfaq said. "For example, a monsoon that usually starts in the first week of June in South Asia and West Africa may be delayed as long as 15 (days) to 20 days or even an entire month over parts of these regions by the end of the 21st century."Although the simulations also showed a delay in the end of the rainy season, otherwise known as monsoon demise, this shift was not nearly as dramatic as the delay in monsoon onset, shortening the length of the entire monsoon season. The researchers also discovered that affected monsoon regions are likely to see more precipitation during that period, leading to more intense rains. Conversely, the rest of the year would see longer dry periods.This increased seasonality could exacerbate the prevalence of floods, droughts, wildfires and other extreme climate events that already pose challenges to these regions. Significant changes in monsoon behavior could contribute to outbreaks of vector-borne diseases, such as cholera, dengue and malaria.Since agricultural activities in monsoon regions are typically timed to coincide with the periodic onset and demise of the rainy season, these factors could alter the production of rain-dependent crop yields."More than half of the world's arabica coffee supply is produced in Brazil, and more than 70% of the cacao used to make chocolate comes from West Africa, whereas more than one-third of rice exports come from India and Pakistan," Ashfaq said. "If regional agriculture is subjected to monsoon onset delays and shorter rainy seasons, production of these types of commodities will be reduced and have a significant impact on the global economy."Many countries located in these regions rely on hydropower to generate electricity, including Brazil, which produces 75% of its energy via this method. Shorter monsoon seasons would not provide enough rainfall at the correct time to supply adequate power without overhauling current operations.In addition to identifying potential monsoon changes and their implications, the team also investigated the root causes responsible for these shifts.In the absence of organized weather systems and a sustained moisture supply, the relatively dry pre-monsoon season receives only intermittent and convective rainfall, which is thermally driven. Lands in these regions get warmer every year during the pre-monsoon period, commonly reaching surface temperatures of 120 degrees Fahrenheit. The combination of convective precipitation warming the upper atmosphere and hot surface conditions warming the lower atmosphere causes disparities between warm air over the land and ocean that force the dry season to give way to monsoon rains.However, the simulations revealed that a continuous increase in global emissions will make the pre-monsoon environment less conducive for convective precipitation, which will delay the warming of upper atmosphere and the transition from the dry to the rainy season. One key factor the researchers determined will decrease convective rainfall during the pre-monsoon period is the formation of a deeper and less saturated boundary layer -- a part of the lower atmosphere where moisture and energy are exchanged between the land and the atmosphere."The upward force needed to lift air parcels to their level of free convection increases with the depth of the boundary layer," Ashfaq said. "And the warmer the atmosphere, the more moisture needed for convective instability, which is essential for the development of thunderstorms. Fulfilling the requirement during the pre-monsoon period is challenging because of the limited moisture supply as winds blow away from the land."The team will contribute their CORDEX simulations to the regional climate change chapter of the next IPCC assessment.This research used resources of the Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility located at ORNL. The team received support from the National Climate Computing Research Center, a collaboration between DOE and the National Oceanic and Atmospheric Administration.
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629120248.htm
|
Historic floods reveal how salt marshes can protect us
|
Coastal wetlands like salt marshes are increasingly recognized as valuable natural defenses that protect coasts against strong wave attacks. Yet their performance during real-world, extreme storms has rarely been told. By digging into major historic records of flood disasters, a research team led by scientists from the Royal Netherland Institute for Sea Research (NIOZ), Delft University of Technology, Deltares and Antwerp University, reveal in a publication this week in
|
Salt marshes have reduced the number of dike breaches during the well-known 1717 historic flood disaster. More interestingly, the 1953 flood disaster also tells us that salt marshes are not only 'wave absorbers' that ease wave attacks on the dike, but are also 'flood fighters' that lower the flood depth by limiting the size of breaches when the dike would fail during severe storms. And having smaller and shallower breaches because of salt marsh protection can save many lives.Rising sea levels and stronger storms raise coastal flood risks and inspire development of new strategy of flood dense: supplementing engineered structures with coastal wetlands like salt marshes. Although we have learnt from experiments and models that these natural buffers are 'wave absorbers' that reduce storm impact, it is unclear whether and how they can indeed add considerable safety to engineered defenses during severe, real world storms. 'Evidence from two notorious flood disasters that killed thousands of people after dike breaching: 1717 Christmas flood and 1953 North Sea flood, however, show that salt marshes have already displayed their role of 'flood fighter' for hundreds of years', says Zhenchang Zhu, the leading author of this paper, who conducted this research at NIOZ, but is currently working at Guangdong University of Technology, China. 'Salt marshes not only reduced the number and total width of dike breaches during the 1717 Christmas flood, but was also found to confine the breach depth during the 1953 North Sea flood. Especially the latter, previously unknown function of natural defenses, can greatly reduce flood damage by lowing inundation depth', Zhu continues.What can we learn from historic lessons? 'Flood defenses combining green and gray features are actually more beneficial than considered earlier. Beyond wave attenuation, salt marshes can lower flood impacts simply by limiting the size of dike breach, and continues to do so under sea level rise', Zhu adds. This generally overlooked function of salt marshes is actually more applicable than wave dissipation, as it is not limited to wave-exposed locations. To harness natural defense, marshes ideally have to be preserved or developed at the seaside of the dike to buffer the waves. This may, however, not always be possible. The study implies that even in this situation, it may still be possible to enhance coastal safety by creating salt marshes in between double dikes, where a secondary more landward dike is present and the most seaward primary dike is opened to allow natural processes to ensure marsh development. Despite no longer useful for wave reduction, such marshes are still very helpful for flood protection by making the landward dike more stable during extreme storms and buffer the effects of the rising sea in the long run. 'Overall this research enables novel designs of nature-based coastal defenses by smartly harnessing different natural flood defense functions', says Zhenchang Zhu.
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629120210.htm
|
Global warming will cause ecosystems to produce more methane than first predicted
|
New research suggests that as the Earth warms natural ecosystems such as freshwaters will release more methane than expected from predictions based on temperature increases alone.
|
The study, published today in The production and removal of methane from ecosystems is regulated by two types of microorganisms, methanogens -- which naturally produce methane -- and methanotrophs that remove methane by converting it into carbon dioxide. Previous research has suggested that these two natural processes show different sensitivities to temperature and could therefore be affected differently by global warming.Research led by Queen Mary University of London and the University of Warwick studied the impact of global warming on freshwater microbial communities and methane emissions by observing the effect of experimental warming of artificial ponds over 11 years. They found that warming produced a disproportionate increase in methane production over methane removal, resulting in increased methane emissions that exceeded temperature-based predictions.Professor Mark Trimmer, Professor of Biogeochemistry at Queen Mary, said: "Our observations show that the increase in methane emissions we see is beyond what you could predict based on a simple physiological response to the temperature increase. Long-term warming also changes the balance in the methane-related microbial community within freshwater ecosystems so they produce more methane while proportionately less is oxidised to carbon dioxide. As methane is a far more potent greenhouse gas than carbon dioxide, together these effects increase the global warming potential of the carbon gases released from these ecosystems."The experimental observations were supported by a meta-analysis of available data on methane emissions collected from wetlands, forests and grasslands worldwide, which showed that naturally warmer ecosystems also produce disproportionately more methane.Professor Trimmer, said: "Our findings fit with what we see in the real world for a wider variety of ecosystems. Together these results suggest that as Earth temperatures increase through global warming, natural ecosystems will continually release more methane into the atmosphere."Dr Kevin Purdy, Associate Professor of Microbial Ecology at Warwick, added: "Our studies have led to a better understanding of how global warming can affect methane emissions from freshwaters. This means that future predictions of methane emissions need to take into account how ecosystems and their resident microbial communities will change as the planet warms."Methane is a powerful greenhouse gas with some 28 times the global warming potential of carbon dioxide over a 100 year period. Over 40 per cent of methane is released from freshwaters such as wetlands, lakes and rivers making them a major contributor to global methane emissions.
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629120135.htm
|
How volcanoes explode in the deep sea
|
Explosive volcanic eruptions are possible deep down in the sea -- although the water masses exert enormous pressure there. An international team reports in the journal
|
Most volcanic eruptions take place unseen at the bottom of the world's oceans. In recent years, oceanography has shown that this submarine volcanism not only deposits lava but also ejects large amounts of volcanic ash."So even under layers of water kilometers thick, which exert great pressure and thus prevent effective degassing, there must be mechanisms that lead to an 'explosive' disintegration of magma," says Professor Bernd Zimanowski, head of the Physical-Volcanological Laboratory of Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.An international research group led by Professors James White (New Zealand), Pierfrancesco Dellino (Italy) and Bernd Zimanowski (JMU) has now demonstrated such a mechanism for the first time. The results have been published in the journal The lead author is Dr. Tobias Dürig from the University of Iceland, a JMU alumnus and former Röntgen Award winner of the JMU Institute of Physics. Before he went to Iceland, Dürig was a member of the research groups of Professor Zimanowski and Professor White.The team did research at the Havre Seamount volcano lying northwest of New Zealand at a depth of about 1,000 metres below the sea surface. This volcano erupted in 2012, and the scientific community became aware of it.The eruption created a floating carpet of pumice particles that expanded to about 400 square kilometres -- roughly the size of the city of Vienna. Now a diving robot was used to examine the ash deposits on the seabed. From the observational data the group of James White detected more than 100 million cubic meters of volcanic ash.The diving robot also took samples from the seafloor, which were then used in joint experimental studies in the Physical-Volcanological Laboratory of JMU."We melted the material and brought it into contact with water under various conditions. Under certain conditions, explosive reactions occurred which led to the formation of artificial volcanic ash," explains Bernd Zimanowski. The comparison of this ash with the natural samples showed that processes in the laboratory must have been similar to those that took place at a depth of 1,000 meters on the sea floor.Zimanowski describes the decisive experiments: "In the process, the molten material was placed under a layer of water in a crucible with a diameter of ten centimeters and then deformed with an intensity that can also be expected when magma emerges from the sea floor. Cracks are formed and water shoots abruptly into the vacuum created. The water then expands explosively. Finally, particles and water are ejected explosively. We lead them through an U-shaped tube into a water basin to simulate the cooling situation under water." The particles created in this way, the "artificial volcanic ash," corresponded in shape, size and composition to the natural ash."With these results, we now have a much better understanding of how explosive volcanic eruptions are possible under water," says the JMU professor. Further investigations should also show whether underwater volcanic explosions could possibly have an effect on the climate."With submarine lava eruptions, it takes a quite long time for the heat of the lava to be transferred to the water. In explosive eruptions, however, the magma is broken up into tiny particles. This may create heat pulses so strong that the thermal equilibrium currents in the oceans are disrupted locally or even globally." And those very currents have an important impact on the global climate.There are around 1,900 active volcanoes on land or as islands. The number of submarine volcanoes is estimated to be much higher. Exact numbers are not known because the deep sea is largely unexplored. Accordingly, most submarine volcanic eruptions go unnoticed. Submarine volcanoes grow slowly upwards by recurring eruptions. When they reach the water surface, they become volcanic islands -- like the active Stromboli near Sicily or some of the Canary Islands.
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629090014.htm
|
Soft coral garden discovered in Greenland's deep sea
|
A deep-sea soft coral garden habitat has been discovered in Greenlandic waters by scientists from UCL, ZSL and Greenland Institute of Natural Resources, using an innovative and low-cost deep-sea video camera built and deployed by the team.
|
The soft coral garden, presented in a new The study has direct implications for the management of economically important deep-sea trawl fisheries, which are immediately adjacent to the habitat. The researchers hope that a 486 km2 area will be recognised as a 'Vulnerable Marine Ecosystem' under UN guidelines, to ensure that it is protected.PhD researcher Stephen Long (UCL Geography and ZSL (Zoological Society London)), first author on the study, said: "The deep sea is often over-looked in terms of exploration. In fact we have better maps of the surface of Mars, than we do of the deep sea."The development of a low-cost tool that can withstand deep-sea environments opens up new possibilities for our understanding and management of marine ecosystems. We'll be working with the Greenland government and fishing industry to ensure this fragile, complex and beautiful habitat is protected."The soft coral garden discovered by the team exists in near total darkness, 500m below the surface at a pressure 50 times greater than at sea-level. This delicate and diverse habitat features abundant cauliflower corals as well as feather stars, sponges, anemones, brittle stars, hydrozoans bryozoans and other organisms.Dr Chris Yesson (ZSL), last author on the study, said "Coral gardens are characterised by collections of one or more species (typically of non-reef forming coral), that sit on a wide range of hard and soft bottom habitats, from rock to sand, and support a diversity of fauna. There is considerable diversity among coral garden communities, which have previously been observed in areas such as northwest and southeast Iceland."The discovery is particularly significant given that the deep sea is the most poorly known habitat on earth, despite being the biggest and covering 65% of the planet. Until very recently, very little was known about Greenland's deep-sea habitats, their nature, distribution and how they are impacted by human activities.Surveying the deep sea has typically proved difficult and expensive. One major factor is that ocean pressure increases by one atmosphere (which is the average atmospheric pressure at sea level) every 10 metres of descent. Deep-sea surveys therefore have often only been possible using expensive remote operating vehicles and manned submersibles, like those seen in Blue Planet, which can withstand deep-sea pressure.The UK-Greenland research team overcame this challenge by developing a low-cost towed video sled, which uses a GoPro video camera, lights and lasers in special pressure housings, mounted on a steel frame.The lasers, which were used to add a sense of scale to the imagery, were made by combining high-powered laser pointers with DIY housings made at UCL's Institute of Making, with help from UCL Mechanical Engineering.The team placed the video sledge -- which is about the size of a Mini Cooper -- on the seafloor for roughly 15 minutes at a time and across 18 different stations. Stills were taken from the video footage, with 1,239 images extracted for further analysis.A total of 44,035 annotations of the selected fauna were made. The most abundant were anemones (15,531) and cauliflower corals (11,633), with cauliflower corals observed at a maximum density of 9.36 corals per square metre.Long said: "A towed video sled is not unique. However, our research is certainly the first example of a low-cost DIY video sled led being used to explore deep-sea habitats in Greenland's 2.2million km² of sea. So far, the team has managed to reach an impressive depth of 1,500m. It has worked remarkably well and led to interest from researchers in other parts of the world."Dr Yesson added: "Given that the ocean is the biggest habitat on earth and the one about which we know the least, we think it is critically important to develop cheap, accessible research tools. These tools can then be used to explore, describe and crucially inform management of these deep-sea resources."Dr Martin Blicher (Greenland Institute of Natural Resources) said: "Greenland's seafloor is virtually unexplored, although we know is it inhabited by more than 2000 different species together contributing to complex and diverse habitats, and to the functioning of the marine ecosystem. Despite knowing so little about these seafloor habitats, the Greenlandic economy depends on a small number of fisheries which trawl the seabed. We hope that studies like this will increase our understanding of ecological relationships, and contribute to sustainable fisheries management."
|
Geography
| 2,020 |
June 29, 2020
|
https://www.sciencedaily.com/releases/2020/06/200629090012.htm
|
Gold mining restricts Amazon rainforest recovery
|
Gold mining significantly limits the regrowth of Amazon forests, greatly reducing their ability to accumulate carbon, according to a new study. The researchers warn that the impacts of mining on tropical forests are long-lasting and that active land management and restoration will be necessary to recover tropical forests on previously mined lands.
|
Gold mining has rapidly increased across the Amazon in recent years, especially along the Guiana Shield, where it is responsible for as much as 90% of total deforestation. The Shield encompasses Guyana, Suriname, French Guiana, Venezuela and small parts of Colombia and northern Brazil, and its forests hold roughly twenty billion tonnes of aboveground carbon in its trees.The ability of tropical forests to recover from gold mining activities has remained largely unquantified. Now, an international study led by the University of Leeds is the first to provide detailed field-based information on the regeneration of forests in Guyana after gold mining, and the first ground-based estimate of carbon sink lost as a result of gold mining activities across the Amazon.The team's findings, published in the They estimate that mining-related deforestation results in the annual loss of over two million tons of forest carbon across the Amazon. The lack of forest regrowth observed following mining suggests that this lost carbon cannot be recovered through natural regeneration.Lead author Dr Michelle Kalamandeen, began this research as a postgraduate researcher in the School of Geography at Leeds she is now a postdoctoral researcher at Cambridge University. She said: "This study shows that tropical forests are strongly impacted by mining activities, and have very little capacity to re-establish themselves following mining."Our results clearly show the extraction process has stripped nitrogen from the soil, a critical component to forest recovery, and in many cases directly contributed to the presence of mercury within neighbouring forests and rivers. Active mining sites had on average 250 times more mercury concentrations than abandoned sites."Not only does this have serious consequences for our battle against global warming by limiting Amazonian forests' ability to capture and store carbon, but there is also a larger implication of contaminating food sources especially for indigenous and local communities who rely on rivers."A positive finding from this study shows that overburden sites, areas where topsoil is deposited during the mining process, recorded similar recovery rates as other Central and South American secondary tropical forests abandoned after agriculture or pasture."Active management and enforcement of laws is clearly needed to ensure recovery and to safeguard communities and there are methods available, such as replacing the soil using the overburdens at abandoned sites. But there is an urgent need for large-scale recovery management to be tested and implemented."We could be facing a race against the clock. The current crisis is significantly increasing the demand for gold, given its perceived role as an economic stabiliser. With current gold price more than US$1700 per ounce and estimated to reach US$2000-3000 in the coming months, many artisanal and small-scale miners are already rapidly responding to this increase in pricing, and the weakening of environmental laws and policies as we've seen in Brazil, leading to further deforestation in the Amazon."The team used forest inventory plots installed on recently abandoned mines in two major mining regions in Guyana, and re-censused the sites 18 months later. The study analysed soil samples and determined individual trees' above-ground biomass -- the tree's living plant material -- to determine recovery and chemical changes caused by mining.Their results suggest that forest recovery is more strongly limited by severe mining-induced depletion of soil nutrients, especially nitrogen, rather than by mercury contamination. The high rate of mercury does however have serious implications for negative impacts on food security, water supply and local biodiversity.Study co-author, Dr David Galbraith, Associate Professor in Earth System Dynamics at Leeds, said: "Currently approximately 1.3 million square kilometres of the Amazon is under prospecting for mining activities."This research provides support to local and national governance structures to critically approach policy implementation and development for land management, including how and where mining occurs, and more stringent monitoring and action for forest recovery. It shows that carefully planned active restoration projects will be critical in this regard."But responsibility lies beyond remediation efforts to mitigate the damage done. Investors and consumers alike need increased awareness and accountability of the environmental footprints of gold mining."The Guyana Geology and Mines Commission (GGMC) who supported the fieldwork are optimistic that the results from this research will help in making more informed decisions for their reclamation policies and programmes, monitoring and enforcement.Mr Newell Dennison, Commissioner of the GGMC said: "The research results showed two important aspects: that overburden areas recovered relatively well and there was limited recovery in mining pits and tailing ponds. The latter being areas where we need improved management. The more data we can accumulate for recovery of secondary forests in mined out areas, the better we are all positioned for the implementation of effective programmes and operations that aid in the recovery of our rainforests. We look forward to working with Dr Kalamandeen and her team in the future."The Guyana Forestry Commission (GFC) expressed gratitude and appreciation to the research team for the important and impressive empirical work done in [this] paper.Mr Gavin Agard, Commissioner of the GFC said: "We expect that this scientific work has greatly improved Guyana's baseline and understanding of the forest degradation impacts of mining with respect to biomass recovery and sets a foundation for more dynamic, focused studies to advise planning and policy for improving secondary forest growth and restoring biomass capacity."The findings and recommendations from this study will significantly impact policy and management strategies for forest restoration and rehabilitation in mined-out areas, which is a key objective for Guyana under the Paris Agreement of the UNFCCC."The contribution of deforestation and degradation to climate change cannot be ignored, and thus we welcome the contributions of this research team to build and improve our communal knowledge and understanding of our changing forests as we continue to pursue the highest standards of sustainable forestry in Guyana."
|
Geography
| 2,020 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.