patrickbdevaney/mia9 · Datasets at Hugging Face

text stringlengths 0 6.44k
Our interpretation of these results is that northern Florida Bay has been transitioning away from
a freshwater marsh estuarine environment towards a marine environment over the last two decades.
While this transition appears to be essentially continuous in Little Madeira Bay since 1994, at the lower
reach of Taylor Slough (TR), hydrologic cycles appear to be transforming from marsh-dominated
dynamics to ocean-dominated since 2000. These shifts in hydrologic cycles are consistent with
increasing mean sea level (Figure 12) and the onset of accelerated water level exceedances as sea
level rises (Figure 10). In the middle-reaches of Taylor Slough represented by station E146, there
were periods of negative MOI during 2003 and 2006 (Figure 13) reflected in a stasis of the integrated
MOI over this period (Figure 14), but the overall assessment is that there is no evidence of emerging
ocean-dominated hydrologic cycles.
J. Mar. Sci. Eng. 2017, 5, 31 16 of 26
Figure 14. Integral over time of the Marsh-to-Ocean Index (MOI) at: (a) Little Madeira Bay (LM);
(b) Taylor River (TR); and (c) Taylor Slough (E146).
4. Discussion
South Florida is ranked ninth globally among urban areas with human populations exposed to sea
level rise impacts and first in terms of exposed assets [28]. South Florida is equally rich in natural assets
with national parks circumscribing the southern peninsula protecting vital freshwater ecosystems that
sustain both natural and human biomes. The exceedingly flat topography and low elevations provide
ideal conditions for the expansion of marine bays and estuaries into existent freshwater marshes, civil
infrastructure and human habitats, issues recognized by regional governments planning for future sea
levels. Such planning efforts rely on global projections without a probabilistic estimate of sea level
likelihood, and focus on urban areas. Here, we examine projected impacts based on a local sea level
rise projection with explicit probabilities corresponding to the median and 99th percentiles focusing
on the estuarine coastal fringe along the southern end of the peninsula. This fringe is generally lower
in elevation than the urbanized east coast, and its natural condition provides an optimal setting to
monitor sea level rise and landscape transformation.
Inundation projections indicate dramatic changes in landscape along the southern peninsula
over the 21st century with the submergence of low-lying urban and suburban areas, as well as
land surrounding cooling canals at the Turkey Point nuclear power plant. In the Everglades, it
appears that substantial portions of existent freshwater marshes will be converted to estuarine and
shallow marine zones with the potential for mean sea level to span the interior of the peninsula along
Shark River Slough.
A fundamental landscape feature of the southern peninsula is a low, narrow ridge separating the
marine and estuarine waters of Florida Bay from freshwater marshes of the southern Everglades. When
sea levels rise above this ridge, a pronounced environmental transformation into a marine-dominated
landscape is expected. We can anticipate this change by applying sea level rise projections to recent
exceedance statistics at the ridge elevation to identify a tipping point horizon where water level
exceedances above this elevation will grow, as well as when the elevation is forecast to become
submarine, signaling a complete transformation to marine or estuarine conditions. Doing so, we find
that circa 2040, the coastal region of Little Madeira Bay will enters the transition of accelerating water
J. Mar. Sci. Eng. 2017, 5, 31 17 of 26
level exceedances above the coastal ridge, and between 2050 and 2070, the area is expected to be
transformed into a marine-dominated landscape.
Transformations along the southern peninsula are inexorably coupled to ecological changes and
feedbacks with the coastal landscape consisting of a dynamic surficial layer of wetland soil overlying a
karstic surficial aquifer. Freshwater soils of mostly organic-rich peat support the ridge-and-slough
landscape and tree islands, while coastal wetlands such as salt marshes and mangroves contain
substantial organic matter along with varying amounts of inorganic sediment washed in by tides,
waves or storm surge. The conversion of coastal marshes to open water from saltwater intrusion
and sea-level rise is often accompanied by peat collapse and deterioration, releasing large amounts
of sequestered carbon. It is estimated that mangrove forests in the Everglades store 145 tonnes per
hectare [29].
These coastal wetlands possess a limited capacity to stabilize and maintain existing coastal barriers
through accretion of organic matter and storm-derived sediment with an average accretion rate of
1–3 mm/year with more rapid accretion rates possible for short periods of time [30]. Global rates of sea
level rise are currently estimated at 3.4 mm/year [31], and our data find local rates of 4 mm/year over
the last decade. In view of the established and expected acceleration of sea level rise, the landscape
may have reached a tipping point unable to sustain spatially-static coastal mangrove forests. Indeed,
vegetation loss along the coast is expressed in a “white zone” of low productivity that has been shifting
inland over the past 70 years [3,32], and models of expected mangrove proliferation suggest that a
66-cm sea level rise corresponding to year 2070 under the high sea rise projection and 2100 under the
low scenario will transform 2000 square kilometers of freshwater marsh into mangrove forests [33].
While inundation projections point to expected changes, examination of water levels allow us
to detect and quantify an acceleration of water level exceedances over the last decade. Such an
acceleration is a natural product of rising sea levels against a fixed elevation whether the change in sea
level itself is linear or accelerating, and we find that exponential doubling times for these exceedances
are on the order of one to two decades. Ecological transformation from freshwater to saltwater biomes
is driven by the spatial and temporal extent of these saltwater inundations, and in Table 6, we list the
change in water level exceedances per year at elevation thresholds above the 90th percentile mean
water levels in 1995. Here, we see that in the marine portion of Florida Bay at Murray Key (MK),
high-water level exceedances have increased from 2–17% of the days per year over the last two decades,
while along the coastal margins, these exceedances have changed from a twice-monthly occurrence,
likely at the spring tides, to a nearly every-other-day occurrence.
Table 6. Number of days per year of water level exceedance in 1995 and 2015.
Station MK LM LS MD
Threshold 40 cm 40 cm 40 cm 90 cm
Year 1995 2015 1995 2015 1995 2015 1995 2015
Days 6 61 27 161 34 133 29 149
Percent Days 2 17 7 44 9 36 8 41
Questions regarding the spatial progression of sea level rise impacts have been addressed with
inundation and exceedance projections; however, the presence of hydrographic records spanning
the marine-to-freshwater interface provides an opportunity to identify spatially-explicit time series
revealing a dynamic transition of water levels from marsh to ocean-dominated. This motivates us to
introduce the Marsh-to-Ocean transformation Index (MOI) as a metric to quantify these changes. We
find that since 1994, there is a cumulative increase in ocean-dominated hydrographic signals in Little
Madeira Bay (LM), as well in the lower reach of Taylor Slough (TR). Farther upstream at station E146,
there is no cumulative evidence of ocean influence.
J. Mar. Sci. Eng. 2017, 5, 31 18 of 26
5. Conclusions
Collectively, the data and analysis present a cohesive picture that South Florida landscapes
and ecosystems are experiencing a transformation of coastal environments into marine-dominated
conditions. Such a transformation will accrue benefits for marine biomes, while decreasing the
productivity of coastal freshwater aquifers and presenting challenges for existent freshwater habitats,
as well as human infrastructure and habitation.
It is important to note that these projections are for mean sea level and do not consider inundation
due to tides or storms. Impacts from tidal inundation will first be noticed at spring tides and then from
daily high tides several years or even a decade prior to mean sea level effects. These events will provide
opportunities to study the impacts and responses of increasingly frequent inundation events prior to
the transformation of existent coastal fringes and freshwater ecosystems into marine-dominated areas.
Further, the projections do not incorporate contributions in the event of Antarctic ice-sheet collapse

Our interpretation of these results is that northern Florida Bay has been transitioning away from

a freshwater marsh estuarine environment towards a marine environment over the last two decades.

While this transition appears to be essentially continuous in Little Madeira Bay since 1994, at the lower

reach of Taylor Slough (TR), hydrologic cycles appear to be transforming from marsh-dominated

dynamics to ocean-dominated since 2000. These shifts in hydrologic cycles are consistent with

increasing mean sea level (Figure 12) and the onset of accelerated water level exceedances as sea

level rises (Figure 10). In the middle-reaches of Taylor Slough represented by station E146, there

were periods of negative MOI during 2003 and 2006 (Figure 13) reflected in a stasis of the integrated

MOI over this period (Figure 14), but the overall assessment is that there is no evidence of emerging

ocean-dominated hydrologic cycles.

J. Mar. Sci. Eng. 2017, 5, 31 16 of 26

Figure 14. Integral over time of the Marsh-to-Ocean Index (MOI) at: (a) Little Madeira Bay (LM);

(b) Taylor River (TR); and (c) Taylor Slough (E146).

4. Discussion

South Florida is ranked ninth globally among urban areas with human populations exposed to sea

level rise impacts and first in terms of exposed assets [28]. South Florida is equally rich in natural assets

with national parks circumscribing the southern peninsula protecting vital freshwater ecosystems that

sustain both natural and human biomes. The exceedingly flat topography and low elevations provide

ideal conditions for the expansion of marine bays and estuaries into existent freshwater marshes, civil

infrastructure and human habitats, issues recognized by regional governments planning for future sea

levels. Such planning efforts rely on global projections without a probabilistic estimate of sea level

likelihood, and focus on urban areas. Here, we examine projected impacts based on a local sea level

rise projection with explicit probabilities corresponding to the median and 99th percentiles focusing

on the estuarine coastal fringe along the southern end of the peninsula. This fringe is generally lower

in elevation than the urbanized east coast, and its natural condition provides an optimal setting to

monitor sea level rise and landscape transformation.

Inundation projections indicate dramatic changes in landscape along the southern peninsula

over the 21st century with the submergence of low-lying urban and suburban areas, as well as

land surrounding cooling canals at the Turkey Point nuclear power plant. In the Everglades, it

appears that substantial portions of existent freshwater marshes will be converted to estuarine and

shallow marine zones with the potential for mean sea level to span the interior of the peninsula along

Shark River Slough.

A fundamental landscape feature of the southern peninsula is a low, narrow ridge separating the

marine and estuarine waters of Florida Bay from freshwater marshes of the southern Everglades. When

sea levels rise above this ridge, a pronounced environmental transformation into a marine-dominated

landscape is expected. We can anticipate this change by applying sea level rise projections to recent

exceedance statistics at the ridge elevation to identify a tipping point horizon where water level

exceedances above this elevation will grow, as well as when the elevation is forecast to become

submarine, signaling a complete transformation to marine or estuarine conditions. Doing so, we find

that circa 2040, the coastal region of Little Madeira Bay will enters the transition of accelerating water

J. Mar. Sci. Eng. 2017, 5, 31 17 of 26

level exceedances above the coastal ridge, and between 2050 and 2070, the area is expected to be

transformed into a marine-dominated landscape.

Transformations along the southern peninsula are inexorably coupled to ecological changes and

feedbacks with the coastal landscape consisting of a dynamic surficial layer of wetland soil overlying a

karstic surficial aquifer. Freshwater soils of mostly organic-rich peat support the ridge-and-slough

landscape and tree islands, while coastal wetlands such as salt marshes and mangroves contain

substantial organic matter along with varying amounts of inorganic sediment washed in by tides,

waves or storm surge. The conversion of coastal marshes to open water from saltwater intrusion

and sea-level rise is often accompanied by peat collapse and deterioration, releasing large amounts

of sequestered carbon. It is estimated that mangrove forests in the Everglades store 145 tonnes per

hectare [29].

These coastal wetlands possess a limited capacity to stabilize and maintain existing coastal barriers

through accretion of organic matter and storm-derived sediment with an average accretion rate of

1–3 mm/year with more rapid accretion rates possible for short periods of time [30]. Global rates of sea

level rise are currently estimated at 3.4 mm/year [31], and our data find local rates of 4 mm/year over

the last decade. In view of the established and expected acceleration of sea level rise, the landscape

may have reached a tipping point unable to sustain spatially-static coastal mangrove forests. Indeed,

vegetation loss along the coast is expressed in a “white zone” of low productivity that has been shifting

inland over the past 70 years [3,32], and models of expected mangrove proliferation suggest that a

66-cm sea level rise corresponding to year 2070 under the high sea rise projection and 2100 under the

low scenario will transform 2000 square kilometers of freshwater marsh into mangrove forests [33].

While inundation projections point to expected changes, examination of water levels allow us

to detect and quantify an acceleration of water level exceedances over the last decade. Such an

acceleration is a natural product of rising sea levels against a fixed elevation whether the change in sea

level itself is linear or accelerating, and we find that exponential doubling times for these exceedances

are on the order of one to two decades. Ecological transformation from freshwater to saltwater biomes

is driven by the spatial and temporal extent of these saltwater inundations, and in Table 6, we list the

change in water level exceedances per year at elevation thresholds above the 90th percentile mean

water levels in 1995. Here, we see that in the marine portion of Florida Bay at Murray Key (MK),

high-water level exceedances have increased from 2–17% of the days per year over the last two decades,

while along the coastal margins, these exceedances have changed from a twice-monthly occurrence,

likely at the spring tides, to a nearly every-other-day occurrence.

Table 6. Number of days per year of water level exceedance in 1995 and 2015.

Station MK LM LS MD

Threshold 40 cm 40 cm 40 cm 90 cm

Year 1995 2015 1995 2015 1995 2015 1995 2015

Days 6 61 27 161 34 133 29 149

Percent Days 2 17 7 44 9 36 8 41

Questions regarding the spatial progression of sea level rise impacts have been addressed with

inundation and exceedance projections; however, the presence of hydrographic records spanning

the marine-to-freshwater interface provides an opportunity to identify spatially-explicit time series

revealing a dynamic transition of water levels from marsh to ocean-dominated. This motivates us to

introduce the Marsh-to-Ocean transformation Index (MOI) as a metric to quantify these changes. We

find that since 1994, there is a cumulative increase in ocean-dominated hydrographic signals in Little

Madeira Bay (LM), as well in the lower reach of Taylor Slough (TR). Farther upstream at station E146,

there is no cumulative evidence of ocean influence.

J. Mar. Sci. Eng. 2017, 5, 31 18 of 26

5. Conclusions

Collectively, the data and analysis present a cohesive picture that South Florida landscapes

and ecosystems are experiencing a transformation of coastal environments into marine-dominated

conditions. Such a transformation will accrue benefits for marine biomes, while decreasing the

productivity of coastal freshwater aquifers and presenting challenges for existent freshwater habitats,

as well as human infrastructure and habitation.

It is important to note that these projections are for mean sea level and do not consider inundation

due to tides or storms. Impacts from tidal inundation will first be noticed at spring tides and then from

daily high tides several years or even a decade prior to mean sea level effects. These events will provide

opportunities to study the impacts and responses of increasingly frequent inundation events prior to

the transformation of existent coastal fringes and freshwater ecosystems into marine-dominated areas.

Further, the projections do not incorporate contributions in the event of Antarctic ice-sheet collapse