East Coast Sea Levels Rising Fast

A government study says sea levels are rising faster along a stretch of the US East Coast than they are around the globe.

The area covers the Atlantic Coast from Cape Hatteras, North Carolina, to just north of Boston.

US Geological Survey scientists call the 965-kilometer swath a “hot spot” for climbing sea levels caused by global warming. Their study says that since 1990, sea levels in that region have been rising at an annual rate three to four times faster than the global average.

Since then, Norfolk, Virginia’s sea level has jumped about 13 cm, Philadelphia’s 10 centimeters and New York City’s 8 centimeters. The global average is 5 cm.

The study was published on Sunday in the journal Nature Climate Change.

If global temperatures keep rising, the sea level on this portion of the coast by 2100 could rise up to 30 cm over and above the one-meter global surge projected by scientists.

The localized acceleration is thought to be caused by a disruption of Atlantic current circulation.

“As fresh water from the melting of the Greenland Ice Sheet enters the ocean, it disrupts this circulation, causing the currents to slow down,” research oceanographer and study co-author Kara Doran explained.

“When the Gulf stream current weakens, sea levels rise along the coast and the greatest amount of rise happens north of where the Gulf Stream leaves the coast (near Cape Hatteras).”

The hot spot stretches from Cape Hatteras, Northern Carolina to north of Boston, Massachusetts, and includes Philadelphia, and Baltimore.

“Extreme water levels that happen during winter or tropical storms, perhaps once or twice a year, may happen more frequently as sea level rise is added to storm surge,” Doran told AFP.

In the study, European scientists said a 1.5 C rise in global temperatures would see sea levels peak about 1.5 meters above 2000 levels. But warming of 2 C would lift sea levels to 2.7 meters, nearly double.

The UN is targeting a 2 C limit on warming from pre-industrial levels for manageable climate change.

“Many people mistakenly think that the rate of sea level rise is the same everywhere as glaciers and ice caps melt, increasing the volume of ocean water, but other effects can be as large or larger,” said US Geological Survey Director Marcia McNutt.

“As demonstrated in this study, regional oceanographic contributions must be taken into account in planning for what happens to coastal property.”

Though global sea level has been projected to rise roughly 7 meters or more by the end of the 21st century, it will not climb at the same rate at every location. Differences in land movements, strength of ocean currents, water temperatures and salinity can cause regional and local highs and lows in sea level.

“Cities in the hot spot, like Norfolk, New York and Boston already experience damaging floods during relatively low intensity storms,” said Doctor Asbury Sallenger, oceanographer and project leader.