Climate Change and Sea-Level Rise in Florida

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climate change and sea-level rise in florida book coverThe Florida Oceans and Coastal Council has just published “Climate Change and Sea-Level Rise in Florida: An Update of the Effects of Climate Change on Florida’s Ocean and Coastal Resources.” The publication is an update to its 2009 edition, “The Effect of Climate Change on Florida’s Ocean and Coastal Resources.”

Karl Havens, Florida Sea Grant director and a member of the Oceans and Coastal Council, said the update was necessary to reflect the more current, science-based information that is now available on one of the principal drivers of climate change in Florida, rising sea levels.

“We determined that the state of science regarding projected rise in sea level had changed sufficiently to warrant an update on that aspect of climate change impacts,” Havens said.

“We also felt it important to considerably expand the information regarding potential impacts of sea-level rise to the built environment, including such issues as water supply, beach nourishment, transportation infrastructure, and waste water treatment.”

In coming years, the Council plans to issue subsequent updates for the other climate change drivers discussed in the first volume, including greenhouse gases, air temperature, and ocean temperature.

What is Known, Probable, Possible

Excerpts of the document appear below, please refer to the full text for references and complete descriptions. Information is categorized according to the scientific confidence associated with that information. “Probable” statements mean that an effect is highly likely to occur in the future. “Possible” information means that it may occur, but that predicted impacts must be carefully qualified to reflect the level of certainty.

Sea-Level Rise

Florida’s geology, chemistry, biology, and human population have already been, and will continue to be, profoundly affected by rising sea levels. For the past few thousand years, sea level around Florida has been rising very slowly, although a persistent upturn in the rate of sea-level rise has begun in recent decades. Change in sea level from 1970 to 2008Geological studies show that in the more distant past, sea level around Florida and the world rose or fell much more rapidly than in more recent times. The response of ice reservoirs to global warming is the biggest unknown in the projections of sea level over the next century. The rate at which sea level rises is equally as important to coastal resources as how much it rises.

WHAT WE KNOW: Florida sea-level rise can, for most practical societal purposes, be considered to be essentially similar to global sea-level rise throughout the state’s coastal areas. The rate of global sea-level rise increased from the 19th century to the 20th and is still doing so. This rate increase is due to both ocean warming and the contributions from both land-based ice melt from glaciers and the ice sheets of Greenland and Antarctica. The most recent satellite observations confirm global average sea-level rise to be about 80% faster than the best estimate of the IPCC Third Assessment Report.

WHAT IS PROBABLE: Global sea level will continue to rise long after 2100 even if greenhouse gas concentrations are stabilized well before the end of the century. Global average sea level will rise by 0.5–1.0 meter (about 20–40 inches) and possibly more by 2100.

WHAT IS POSSIBLE: Major inputs of water from the melting of high-latitude and high-altitude ice reservoirs could cause a global average sea-level rise of up to two meters this century and several more meters over the subsequent centuries.

Changes in Barrier Islands, Beaches, and Inlets

Beaches and inlets are regional systems of sediment deposition, erosion, and transport. These processes are profoundly affected by changes in sea level and rates of sea-level change as well as by storm events. Scientists and resource managers will be challenged to separate the effects of sea-level changes from the effects of storms and the alterations resulting from beach and inlet management actions.

Changes in Estuaries, Tidal Rivers, and Coastal Forests

Although Florida tide ranges are relatively small, tidal effects extend far inland because much of the state is low, relative to sea level, and flat. Because sea level has been rising only slowly for a long time, tidal wetlands such as mangrove forests and salt marshes have been able to accumulate sediment at the same rate as the rise in sea level and grow into expansive habitats for estuarine and marine life. However, these tidal wetlands are very sensitive to the rate of sea-level rise and will disappear if sea-level rise exceeds their capacity to accumulate sediment. With rising sea levels, sandbars and shoals, estuarine beaches, salt flats, and coastal forests will be altered. Predicted changes in rainfall will alter freshwater inflow from tidal rivers and in turn will affect salinity regimes in estuaries. This is likely to alter the communities of aquatic plants and animals as well as patterns of terrestrial animals that also depend on these waters. Major redistributions of mainland and barrier island sediments may harm or benefit existing wetland, seagrass, or fish and wildlife communities, but these processes cannot be forecast with existing models.

Higher Storm Surge and Impacts on Coastal Infrastructure

Rising sea level has the potential to cause catastrophic damage to coastal communities in Florida, especially as it exacerbates storm surge generated by hurricanes when they hit large urban regions. Before and After photos of Florida Gulf CoastAs sea level continues to rise, deeper waters near shore will translate to higher storm surge, faster flow, higher waves, and hydrodynamic pressure and wave impact loads on buildings near the shoreline, which are likely to exceed their designed capacities by wide margins and suffer significant damage and loss of function.

Threats to Coastal Water Supply and Wastewater Treatment

Sea-level rise already threatens the aquifers that have been the principal source of much of Florida’s drinking water in low-lying coastal areas. This problem will worsen as sea level continues to rise and as withdrawals of water increase for the anticipated growth in Florida’s population.

Increases in Beach Erosion and Renourishment

Florida’s beautiful beaches are a major tourist destination and thus have a high economic value to our state. They also provide critical habitat for marine animals: for example, nesting sites for sea turtles. Alligator Point home after coastal stormOur beaches experience varying degrees of erosion, which is due not only to natural processes such as tropical storms but also to man-made situations, including inlets that enhance downshore sand loss. In areas where there is a net loss of sand, beaches are maintained by renourishment. Rising sea level may have a number of effects on the short- and long-term sustainability of our beaches and on how frequently the sand needs to be replenished.

Impacts on Coastal Planning

Given the substantive impacts that sea-level rise may have on Florida’s coastal communities, there is a need for comprehensive regional planning to develop effective adaptation strategies. Plans are being developed in certain coastal areas, but a large percentage of the state’s coastal communities have yet to contemplate such planning efforts. Because the effects of sea-level rise are likely to be seen first in relation to storm surges, planning for hurricanes and storm surges is at the front line of sea-level rise planning in Florida.

Increased Flooding Risks

Sea-level rise will increase the risk of tidal flooding in coastal areas. Hurricane storm surge and wave heights during hurricanes will be higher with sea-level rise. In low-lying interior areas, stormwater drainage systems will be compromised as sea-level rises, increasing the risk of flooding during heavy rains.