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1 Physical Resources, South Florida Natural Resources Center, National Park Service, Homestead, FL 33030,
2 Biological Resources, South Florida Natural Resources Center, National Park Service, Homestead, FL 33030,
* Correspondence: [email protected]; Tel.: +1-305-224-4250
Received: 12 April 2017; Accepted: 18 July 2017; Published: 28 July 2017
Abstract: South Florida encompasses a dynamic confluence of urban and natural ecosystems strongly
connected to ocean and freshwater hydrologic forcings. Low land elevation, flat topography and
highly transmissive aquifers place both communities at the nexus of environmental and ecological
transformation driven by rising sea level. Based on a local sea level rise projection, we examine
regional inundation impacts and employ hydrographic records in Florida Bay and the southern
Everglades to assess water level exceedance dynamics and landscape-relevant tipping points. Intrinsic
mode functions of water levels across the coastal interface are used to gauge the relative influence and
time-varying transformation potential of estuarine and freshwater marshes into a marine-dominated
environment with the introduction of a Marsh-to-Ocean transformation index (MOI).
Keywords: South Florida; sea level rise; inundation; coastal impacts; water level exceedance
1. Introduction
Sea level rise is not evenly distributed around the globe, and the response of a regional coastline
is highly dependent on local natural and human settings [1]. This is particularly evident at the
southern end of the Florida peninsula where low elevations and exceedingly flat topography provide
an ideal setting for encroachment of the sea. Coastal South Florida is fringed by national parks
including Biscayne and Everglades National Parks, Big Cypress National Preserve and the islandic
Dry Tortugas National Park. This rich natural setting and subtropical climate appeal to human
interests with over six million inhabitants residing along narrow coastal strips along the Atlantic
and Gulf coasts. The sustenance of these natural and human ecosystems is predicated on adequate
freshwater supply, and while South Florida receives an average of 140 cm of rainfall annually, losses to
evaporation are nearly as great as the rainfall itself, and water storage is limited to shallow, permeable
reservoirs and thin surficial aquifers that are experiencing diminishing capacity as rising sea level
drives saltwater infiltration.
Attempts to control the hydrologic resources have resulted in the construction of one of the most
complex and expansive water control projects on the planet with both beneficial and detrimental
impacts on human and natural populations [2,3]. Regional governments recognize the need to assess
and plan for sea level rise implementing a Regional Climate Action Plan [4] with a task force specifically
addressing sea level rise [5]. However, these efforts focus on urban and suburban areas with concern
for property values, transportation, housing, water supply and sewer infrastructure based on global
sea level rise projections that do not reflect local processes and that are not associated with specific
probabilities of occurrence.
Here, we focus on the low-elevation natural areas at the southern end of the peninsula as shown in
Figure 1, as these areas will experience inundation impacts prior to the urban areas, thereby serving as
J. Mar. Sci. Eng. 2017, 5, 31; doi:10.3390/jmse5030031 www.mdpi.com/journal/jmse
J. Mar. Sci. Eng. 2017, 5, 31 2 of 26
sensitive indicators of sea level rise. We evaluate sea level rise inundation impacts under two scenarios,
a low projection and a high projection, based on a synthesis of coupled atmosphere-ocean general
circulation models and tide gauge information reflecting local processes. The high projection represents
an upper percentile (99%) of expected sea level rise given current models and observations, while the
low projection corresponds to a median (50%) sea level rise scenario. Since models, observations and
current scientific understanding are incomplete, these projections are necessarily incomplete and do
not account for a rapid collapse of the Antarctic ice-sheets, a development that is currently unfolding
with potential to render these projections as lower bounds [6,7].
We also examine coastal water level exceedance data, quantifying an exponential increase in
low-elevation exceedances over the last decade. Application of the sea level rise projections allows
us to project these exceedance curves into the future, where one can identify tipping points and time
horizons for the transformation of coastal regions into marine ecosystems. Finally, we introduce a
metric to characterize the transformation of a coastal wetland from a freshwater marsh into a saltwater
marsh based on intrinsic mode functions of water level time series extending landward from the sea.
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Source: Esri, DigitalGlobe,
GeoEye, Earthstar
Geographics, CNES/Airbus
DS, USDA, USGS, AEX,
Getmapping, Aerogrid, IGN,
Legend
# Monitoring Stations
Canals
Biscayne National Park
Everglades National Park
No Data
Canals, Streams, Land Boundary
Pineland
Urban
Agriculture
Mangrove
Fresh Water Marl Prairie
Cypress
Coastal Prairie
Hardwood Hammock
Coastal Marsh
Fresh Water Slough
Water (0-0.91 m)
Water (0.91- 1.82 m)
Water (1.82+ m)
0 5 10 20 Kilometers
Flamingo
Figure 1. Physiographic map of South Florida representing different ecological domains dictated