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|a Past and Projected Trends in Climate and Sea Level for South Florida |h [electronic resource] |b Hydrologic and Environmental Systems Modeling Technical Report. |
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|a [S.l.] : |b South Florida Water Management District, |c 2011-07. |
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|a Please contact the owning institution for licensing and permissions. It is the user's responsibility to ensure use does not violate any third party rights. |
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|a The South Florida Water Management District (SFWMD) is an agency of the state of
Florida that is responsible for managing water resources in a 16-county region that
extends from Orlando to Key West. The SFWMD was created by the State in 1949 as the
local sponsor for the Federal project built by the United States Army Corps of Engineers
(USACE). Charged with safeguarding the region’s water resources, the SFWMD is
responsible for managing and protecting water quality, flood control, natural systems and
water supply. A primary role is to operate and maintain an extensive water management
network of canals and levees, water storage areas, pump stations and other water control
structures.
The SFWMD is also the Local Sponsor in the Federal-State initiative to restore America's
Everglades. The resulting Comprehensive Everglades Restoration Plan (CERP) is the
largest environmental project in North America. Through Federal, State and Local
partnerships, the Greater Everglades, once a free-flowing, natural marsh system in
southern Florida, is being restored under numerous water resources management projects
requiring large investments of time and money (USACE and SFWMD, 1999).
In December 2010, the SFWMD initiated a project to coordinate issues related to climate
change and sea level rise, since future changes in these conditions will affect all aspects
of the SFWMD mission. One task within that project was to prepare a technical report on
trends in sea level rise and climate variability. This report represents the culmination of
several investigations aimed at assessing the current state of knowledge on these issues as
they pertain to south Florida. The first section provides an assessment of natural climate
variability and how it influences the south Florida climate. This is followed by an indepth
analysis of historical trends in precipitation and temperature and their projections
produced by General Circulation Models (GCMs) and Regional Climate Models (RCMs).
Next, sea level rise trends and projections are reviewed including examination of
potential changes to storm surges and coastal drainage capacity, followed by a brief
summary of exploratory hydrologic modeling conducted to understand the water
resources impacts of these projected changes.
Challenges Associated with Climate Change
The low, flat elevation of south Florida coupled with its heavily urbanized coastal
corridors render it particularly sensitive to sea level rise. In addition, the significant
influence that climate teleconnections (i.e. when changes in weather at one location
appear related to weather changes at remote locations) have on the natural variability and
the regional climate of south Florida is now recognized as an important factor. Success
of future infrastructure investments to meet the needs of both the built and natural
environments will require an understanding of the vulnerabilities and impacts of climate
change and sea level rise. Human induced alterations such as ongoing land use changes and possible warming due to greenhouse gasses will complicate the future climate change
outlook, particularly if such drivers affect the physical mechanism responsible for the
natural cycles.
As climate conditions change and sea level rises, south Florida will be concerned with a
number of important issues:
1) Changes in rainfall and evaporation patterns that will alter the amount of
available freshwater, potentially causing more frequent or prolonged periods of
drought, flooding or both
2) Sea level rise resulting in increased saltwater intrusion into the coastal aquifers
and public water supply
3) Sea level rise resulting in reduction of coastal stormwater release capacity.
4) Changes in tropical storm and hurricane activity with increased surge levels,
and
5) Seawater inundation of ecosystems and coastal real estate
Natural Variability
Natural climate variability in the state of Florida is a regional manifestation of climate
oscillations at much larger spatial scales, sometimes global in nature. Temporally, these
large scale oscillations may vary from a few years to many thousands of years. This
report focuses on climate oscillations that had significant influence on the 20th and early
21st centuries’ climate variability, so that a clearer demarcation can be made between
anthropogenic climate change and that of natural climate variability. Even without
anthropogenic causes, Florida has experienced large shifts in climate as evidenced in both
the averages and extremes of meteorologic variables. These shifts can be recognized by
changes in the frequency and intensity of floods (plus other large runoff events) and
droughts. These climate shifts can also be recognized by periods with a larger number of
intense hurricanes versus more tranquil periods. These periods can last for decades, and
could be easily be construed as part of anthropogenic climate change. Specifically, we
identify a number of large scale climate oscillations that influence the regional climate of
Florida including: El Niño-Southern Oscillation (ENSO), Atlantic Multi-decadal
Oscillation (AMO) and the Pacific Decadal Oscillation (PDO). Solar cycles have also
been identified as important contributors to Florida climate variability.
Temperature and Precipitation
A pre-requisite of any climate change investigation is to examine the historical trends in
climatic and other associated environmental data. We have investigated a comprehensive
collection of climate metrics to study historical trends in both the averages and extremes
of precipitation and temperature across the state of Florida. The results of trend analyses
show a general decrease in wet season precipitation. This is most evident for the month
of May and may be tied to a delayed onset of the wet season in Florida. In contrast, there seems to be an increase in the number of wet days during the dry season, especially
during November, December and January. We found that the number of dog days (above
26.7 °C, 80 °F) during the year and during the wet season has increased at many
locations. For the post-1950 period, a widespread decrease in the daily temperature range
(DTR) is observed mainly due to increased daily minimum temperature (Tmin).
Although we did not attempt to formally attribute these trends to natural versus
anthropogenic causes, we infer that the urban heat island effect is at least partially
responsible for the increase in Tmin and its corresponding decrease in DTR at urbanized
stations compared to nearby rural stations.
Climate Projections
We investigated projections of both General Circulation Models (GCMs) and Regional
Climate Models (RCMs) for potential use in planning and operation of water resources
management systems in south Florida and verified the ability of these models to mimic
climatic patterns of the 20th century for which many observations are available. The
seasonality of surface temperature is simulated reasonably well by GCMs, but there are
significant biases in individual models. We found that the skill of GCMs is extremely
poor for reproducing south Florida precipitation. In the case of statistically downscaled
data, the simulation of climatology and the variability of temperature are adequate,
however precipitation values show biases, particularly during the wet season. In general,
the use of dynamically-downscaled variables to compute potential evapotranspiration
appears to provide reasonable results, even though there are significant spatial and
temporal biases.
Sea Level Rise
The south Florida environment is heavily influenced by the Atlantic Ocean and the Gulf
of Mexico which are important drivers of regional weather, climate and coastal
hydrology. It is well known that sea levels are highly variable over geologic time; in fact
the upper layers of most of the Florida peninsula were created from accretion and
deposition in an ancient shallow sea. Even brief consideration of geologic sea level leads
one to expect that portions of the peninsula will eventually be under the sea once again.
We also know that sea levels have been rising since the last glacial maximum, and are
expected to continue rising into the foreseeable future.
As sea level rises, south Florida will be concerned with at least four important issues: 1)
saltwater intrusion into the coastal aquifers and public water supply, 2) reduction of
coastal stormwater release capacity, 3) increased tropical storm and hurricane surge
levels, and 4) seawater inundation of ecosystems and coastal real estate. Strategies to
deal with these issues will require multidisciplinary analysis and cooperation across the
academic, public and private sectors to develop decision-support tools and metrics to
guide public policy directions in response to these challenges. In this report we examine the most recent scientific literature on sea level rise, as well as regional government
projections. A careful analysis of storm surge statistics and their link to teleconnections
highlights the concern for coastal vulnerabilities under rising seas. We also outline
socioeconomic drivers as an emerging area of analysis and suggest modeling strategies to
provide an informational foundation for decision support.
Water Resources Impacts
To assess the hydrological impacts of climate change effects on south Florida, numerical
models can be developed to evaluate alternative scenarios and the concordant water
resources policy changes to mitigate or adapt to the changes. This means that models
will be needed that incorporate the managed system and its operational policies, as well
as the subsurface hydrology impacted by saltwater intrusion (density-dependent flow),
and water quality estimates. Currently there is no single model that addresses all of these
needs. The most widely used and documented hydrologic model for the south Florida
region is the South Florida Water Management Model (SFWMM). We used the
SFWMM to investigate hydrologic conditions in response to changing temperature and
precipitation scenarios, and to a sea level rise scenario. In response to a 1.5 OC warming
and a 10% decrease in precipitation, model results suggest significant water resource
deficiencies in relation to CERP targets for nearly the entire region. A sea level rise of
1.5 ft is projected to fundamentally alter the wetlands, as well the coastal urban areas, of
the southern Florida peninsula with saltwater inundation. Improved modeling
frameworks to address these issues are a primary need. |
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|a Electronic reproduction. |c Florida International University, |c South Florida Water Management District, |d 2015. |f (dpSobek) |n Mode of access: World Wide Web. |n System requirements: Internet connectivity; Web browser software. |
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|a South Florida Water Management District. |
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|a Florida Documents Collection. |
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|a South Florida Collection. |
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|a dpSobek |c Sea Level Rise |
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|u http://dpanther.fiu.edu/dpService/dpPurlService/purl/FI15061841/00001 |y Click here for full text |
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|a http://dpanther.fiu.edu/sobek/content/FI/15/06/18/41/00001/Obeysekera et al_2011_Past and projected trends in climate and sea level for south Florida2thm.jpg |
