What’s the connection between sea level rise and storm surge?

Sea level rise refers to the increase in sea levels both globally and locally. Global averages of sea levels have been increasing due to ocean warming and glacial ice melt. In addition, local sea level rise varies depending on local patterns of sinking land, coastal erosion, and ocean currents. In Beaufort and Port Royal, SC, local sea level has risen 6 inches since 1965 based on data collected at the nearest tide gauge in Fort Pulaski, GA. Some of the first impacts of sea level rise include higher King Tides, more nuisance flooding, and mixing of salt water with freshwater further upriver.

Storm surge typically impacts the same areas threatened by future sea level rise. Storm surge, unlike sea level rise, occurs only when a storm approaches the coast. Storm surge is the rise in water above the normal tide that occurs when winds from a storm push water towards the shore. It can result in coastal flooding and damage. Thus, if a storm occurs during high tide, a community will experience more storm surge than if the same storm had occurred during low tide. FortPulaskiGA

edited SLR picture

Why take action at the local level?

Why should municipal and county governments be discussing sea level rise now?

A recent Winthrop University poll shows an overwhelming amount of coastal residents support planning for sea level rise.  From the poll:

” According to the Winthrop Poll those living in coastal counties are quite familiar with the issue of rising seas with 68% saying that they are very sure or somewhat sure sea-level rise is or will be happening.  That compares to 55.4% of respondents from non-coastal counties.  Statewide 57.3% said that sea levels will rise with only 8% saying that sea levels are and will not rise.   73.3%, support state and local governments taking actions to make South Carolina coastal communities better prepared for sea-level rise and its impacts.

Using the various options for predicted sea level rise (SLR), we calculated the vulnerable land area in Beaufort and Port Royal.

BeaufortSLR Port Royal SLR

One of the goals of community planning is to move the community toward what it should look like in 50 or 100 years, especially when today’s actions either help or hinder the ability of the community to be successful in the future. Three examples of how municipal and county governments provide forward-thinking planning include protecting historic buildings, planning parks and establishing zoning ordinances that define how a community grows.

Communities should include sea level rise on their future planning list because many sea level rise impacts are already being felt, including more frequent higher tides covering low-lying areas. Exceptionally high tides can damage the community’s buried utilities as well as flooding buildings long before these areas are inundated permanently by rising sea level. For example, storm and sewer lines and buried communications infrastructure represent a significant capital expense for any community. Since almost all communities already have difficulty meeting their current financial commitments, preventing future catastrophic economic losses caused by storm tides, magnified by rising sea level, should be a high priority of every coastal community.

Uncertainty in predictions

Why is there so much uncertainty in determining how fast sea level will rise in the future?

There are three reasons for the uncertainty in accurately projecting future sea level rise. (1) Sea level fluctuates annually as the oceans cool down and heat up, and therefore estimates of long term trends in sea level rise require data from many years. (2) Scientists are still discovering new information about how fast the ocean will warm or glacial ice will melt—and both of these factors cause global sea levels to rise. As a result, scientists use different global sea level rise scenarios to estimate how fast and how much sea level will rise (see Figure 2)1. (3) While all scientific models predict that the rate of sea level rise will increase in the future, these models differ because they attempt to predict future global changes that involve complicated environmental interactions, such as an ice-free Arctic Ocean accelerating the rate of Greenland’s glaciers melting, As shown in Figure 2, slight differences in the estimated rate of sea level rise results in large differences when projected a century into the future.

1 Parris, A., et al. 2012. Global Sea Level Rise Scenarios for the United States National Climate Assessment. National Oceanic and Atmospheric Administration. cpo.noaa.gov/sites/cpo/Reports/2012/NOAA_SLR_r3.pdf