Hotspot of accelerated sea-level rise on the Atlantic Coast of North America

 
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A walk by the seaside is a lovely thing, unless that stretch of beach used to be your back yard. While public opinions on threat of climate change are volatile, there is near total consensus in the scientific community: Global warming is happening and its effects are being felt already, particularly in coastal regions.

Rather than rising equally at all points around the globe, local sea levels can be higher or lower than the average depending on circulation patterns, water salinity, gravity effects, and the rotation and shape of the Earth. A 2012 study in the journal Nature Climate Change, “Hotspot of Accelerated Sea-level Rise on the Atlantic Coast of North America,” explores trends in ocean level rise in the Northeastern United States. The researchers, based at the U.S. Geological Survey’s St. Petersburg Coastal and Marine Science Center, analyzed historical tide-gauge records and projected out potential sea-level rises in 60-, 50-, and 40-year windows.

The findings include:

  • Historically, sea levels have been relatively low along the Northeastern U.S. because of the dynamic interplay between the Gulf Stream and other environmental factors. “These low levels could rise with warming and/or freshening of surface water in the subpolar north Atlantic.”
  • From 1950 to 2009 (60-year window), the global rise in sea levels averaged 0.59mm per year, plus or minus 0.26mm. By comparison, in the Northeastern U.S., from Cape Hatteras up to Maine, levels rose 1.97mm, plus or minus 0.64mm — more than three times the global rate.
  • From 1970 to 2009 (40-year window), the global sea levels rose 0.98mm per year, plus or minus 0.33mm. For the Northeast, the rate was 3.80mm per year, plus or minus 1.06mm — nearly four times the global rate.
  • South of Cape Hatteras and north of Boston, changes in sea level are either negative or not statistically different from zero: 0.11mm, plus or minus 0.92mm, to the south; -0.94mm, plus or minus 0.88mm, to the north.
  • If current trends in greenhouse-gas emissions continue, by 2100 the sea level at New York City is projected to rise by 36 to 51cm (14 to 20 inches). In a scenario with lower emissions of greenhouse gases, the increase would be 24 to 36cm (9 to 14 inches).

The researchers call the region of accelerated sea-level rise a “unique 1,000-kilometer-long hotspot,” where the effects of climate change will be disproportionately felt. Major metropolitan areas within this region include Boston, New York, Philadelphia, and Baltimore. “[Sea-level rise] superimposed on storm surge, wave run-up and set-up will increase the vulnerability of coastal cities to flooding, and beaches and wetlands to deterioration,” they state.

Tags: oceans, global warming, science

    Writer: | Last updated: June 25, 2012

    Citation: Sallenger Jr, Asbury H.; Doran, Kara S.; Howd, Peter A. "Hotspot of Accelerated Sea-level Rise on the Atlantic Coast of North America," Nature Climate Change, December 2012, Vol. 2, 884–888. doi:10.1038/nclimate1597.
     

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