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Sea Level Rise

Massachusetts, particularly the southeast coast, is vulnerable to sea level rise. Sea level rise is dependent on melting of ice on land, changing water currents, and expansion of water due to increases in water temperature. Factors contributing to sea level rise in Massachusetts are further amplified by land subsidence or sinking. Other factors contributing to regional increase of sea level rise above the global mean include the collapse of the West Antarctic ice sheet and changes in the Gulf Stream. Without any changes in storm patterns, the frequency of dangerous coastal flooding would more than triple if sea level rises two feet.(1)  At present, global sea level rise is projected at 1 to 4 feet by the year 2100. In Massachusetts, regional factors can contribute to sea level rise ranging from 1 to 6.6 feet by the year 2100.(2)  A study examining five coastal areas, including Boston and Woods Hole, found that projected sea level rise would significantly increase the frequency of 100-year flood events.(4) (5) 

Sea level rises will result in retreat of coastal shoreline, increase in the height of storm surges, and erosion, inundation and flooding of low-lying areas. Considering population density and extensive development along coastal Massachusetts, changes in sea level will have significant impacts to critical facilities, infrastructure, and residential and commercial developments. Existing infrastructure can become damaged or corroded from exposure to saltwater. For example, saltwater will not only accelerate rust damage to rail lines, but also damage signal equipment for rail systems. While the built environment is vulnerable to storm related damage, buildings and infrastructure also hinder the ability of natural coastal systems to buffer and reduce storm damage to inland areas(3)  Natural coastal systems include beaches and sand dunes, salt marshes, and floodplains, The ability of natural coastal systems to buffer against storm damage is limited when these habitats are flooded. Sea level rise will also inundate these natural coastal systems and prevent these ecosystems from filtering pollutants that may enter water bodies.  

Barrier beach and dunes will experience increased erosion rates and over wash.  Breaches to barrier system can expose communities such as Plymouth, Duxbury, and Kingston to storm surges.  Storm surges and damage to infrastructure can result in population displacement.  Sea level rise can also impact availability of drinking water when saltwater intrusion of aquifers occurs.  As mentioned in the Severe Weather Events Climate Profile, flood waters can overwhelm and cause damage to sewage systems.

The graphic shows the monthly mean sea level for (a) Boston, (b) Woods Hole, and (c) Nantucket water level stations. Based on available data, the mean sea level trend ranged from 2.81 millimeters/year in Boston to 3.58 millimeters/year in Nantucket.

NOAA temperature map

The mean sea level trend is 2.81 millimeters/year with a 95% confidence interval of +/- 0.17 mm/yr based on monthly mean sea level data from 1921 to 2014, which is equivalent to a change of 0.92 feet in 100 years.

NOAA temperature map

The mean sea level trend is 2.83 millimeters/year with a 95% confidence interval of +/- 0.18 mm/yr based on monthly mean sea level data from 1932 to 2014, which is equivalent to a change of 0.93 feet in 100 years.

NOAA temperature map

The mean sea level trend is 3.58 millimeters/year with a 95% confidence interval of +/- 0.39 mm/yr based on monthly mean sea level data from 1965 to 2014, which is equivalent to a change of 1.17 feet in 100 years

Source: National Oceanic and Atmospheric Administration (2014)
(a) http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8443970;
(b) http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8447930;
(c) http://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8449130

Footnotes
  1. US Global Change and Research Program (USGCRP).  (2014).  Third National Climate Assessment , Chapter 16: Northeast.  Available from http://nca2014.globalchange.gov/system/files_force/downloads/high/
    NCA3_Full_Report_16_Northeast_HighRes.pdf?download=1
  2. MA EOEEA. (2011).  Massachusetts Climate Change Adaptation Report.  Available from http://www.mass.gov/eea/docs/eea/energy/cca/eea-climate-adaptation-report.pdf
  3. MA Coastal Zone Management.  (2013).  Sea Level Rise: Understanding and Applying Trends and Future Scenarios for Analysis and Planning.  Available from http://www.mass.gov/eea/docs/czm/stormsmart/slr-guidance-2013.pdf.
  4. Kirshen, P., C. Watson, E. Douglas, A. Gontz, J. Lee, and Y. Tian, 2008. Coastal Flooding in the Northeastern United States due to Climate Change. Mitigation and Adaptation Strategies for Global Change 13(5-6): 437-451.
  5. A flood hazard map for Massachusetts depicting FEMA designated 1-in-100 and 1-in-500 chance of flooding annually can be found here.
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