By Seth Borenstein
From Cape Hatteras, N.C., to just north of Boston, sea levels are rising much faster than they are around the globe, putting one of the world's most costly coasts in danger of flooding, government researchers report.
U.S. Geological Survey scientists call the 600-mile swath a "hot spot" for climbing sea levels caused by global warming. Along the region, the Atlantic Ocean is rising at an annual rate three times to four times faster than the global average since 1990, according to the study published Sunday in the journal Nature Climate Change.
It's not just a faster rate, but at a faster pace, like a car on a highway "jamming on the accelerator," said the study's lead author, Asbury Sallenger Jr., an oceanographer at the agency. He looked at sea levels starting in 1950, and noticed a change beginning in 1990.
Since then, sea levels have gone up globally about 2 inches. But in Norfolk, Va., where officials are scrambling to fight more frequent flooding, sea level has jumped a total of 4.8 inches, the research showed. For Philadelphia, levels went up 3.7 inches, and in New York City, it was 2.8 inches.
Climate change pushes up sea levels by melting ice sheets in Greenland and west Antarctica, and because warmer water expands.
Computer models long have projected higher levels along parts of the East Coast because of changes in ocean currents from global warming, but this is the first study to show that's already happened.
By 2100, scientists and computer models estimate that sea levels globally could rise as much as 3.3 feet. The accelerated rate along the East Coast could add about 8 inches to 11 inches more, Sallenger said.
"Where that kind of thing becomes important is during a storm," Sallenger said. That's when it can damage buildings and erode coastlines.
On the West Coast, a National Research Council report released Friday projects an average 3-foot rise in sea level in California by the year 2100, and 2 feet in Oregon and Washington. The land mass north of the San Andreas Fault is expected to rise, offsetting the rising sea level in those two states.
The USGS study suggests the Northeast would get hit harder because of ocean currents. When the Gulf Stream and its northern extension slow down, the slope of the seas changes to balance against the slowing current. That slope then pushes up sea levels in the Northeast. It is like a see-saw effect, Sallenger theorizes.
Scientists believe that with global warming, the Gulf Stream and other ocean currents are slowing and will slow further, Sallenger said.