From: David A Gabel, ENN
Published June 25, 2012 10:16 AM

Sea Level Rise on US Atlantic Coast 3-4 Times Faster than Global Average

The East Coast of the United States is home to many of its major population centers. While some of the early colonizers migrated west, many stayed and built up some of America's great cities, including Portland, Boston, New York, Philadelphia, Norfolk, Charleston, and Miami. Now this region is facing an unprecedented challenge caused by the changing climate. The sea level is rising, and due to a variety of oceanographic and topographic factors, it is rising faster on the US Atlantic Coast than it is globally. The greatest increase will be felt in the "hot zone", from Cape Hatteras, North Carolina to north of Boston, Massachusetts.


United States Geological Survey (USGS) has studied global sea level rise for over 20 years. They found that since 1990, sea level rise in the hot zone was 2-3.7 millimeters per year. Globally, the increase was only 0.6-1.0 millimeters per year over the same period.

In a report published in the journal, Nature Climate Change, USGS suggests that the Atlantic Coast sea level rise in the US is consistent with the slowing of the Atlantic Ocean circulation, sometimes known as the Gulf Stream. The slowing of this current may be tied to changes in water temperature, salinity, and density from the sub polar north Atlantic.

"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 than the so-called 'eustatic' rise," said USGS Director Marcia McNutt. "As demonstrated in this study, regional oceanographic contributions must be taken into account in planning for what happens to coastal property."

Globally, sea level is projected to rise two to three feet by the end of the 21st century, but at different rates around the world. The factors that cause regional disparities include land movements, ocean current strength, water temperature, and salinity.

For the Atlantic "hot zone", sea levels are projected to rise 8 to 11.4 inches more than globally by the year 2100. Cities along this coast already experience intense damaging floods even during low-intensity storms. Ongoing sea level rise will make coastal cities increasingly vulnerable by adding to the height that storm surge waves reach the coast.

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