Sea levels are rising much faster along the US east coast than they are around the globe, putting one of the world's most costly coasts in danger of flooding, government researchers have reported.
US Geological Survey scientists call the 965km swathe a "hot spot" for climbing sea levels caused by global warming.
Along the region, the Atlantic Ocean is rising at an annual rate three to four times faster than the global average since 1990, according to the study published yesterday 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 5cm. But in Norfolk, Virginia, where officials are scrambling to fight more frequent flooding, sea levels have jumped a total of 12.19cm, the research showed.
For Philadelphia, levels went up 9.4cm, and in New York City, it was 7.11cm.
Climate change pushes up sea levels by melting ice sheets in Greenland and west Antarctica, and because warmer water expands.
Computer models have long 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 has already happened.
By 2100, scientists and computer models estimate that sea levels globally could rise as much as 1.01 metres.
The accelerated rate along the east coast of the US could add about 20 to 28cm more, Mr Sallenger said.
"Where that kind of thing becomes important is during a storm," Mr Sallenger said.
Sea level projections matter in coastal states because flood maps based on those predictions can result in restrictions on property development and affect flood insurance rates.
Those estimates became an issue in North Carolina recently when the legislature there proposed using historic figures to calculate future sea levels, rejecting higher rates from a state panel of experts. The North Carolina proposal used data from University of Florida professor Robert Dean, who had found no regional differences in sea-level rise.
Mr Dean said he can't argue with the results from Mr Sallenger's study showing accelerating sea-level rise in the region, but he said it's more likely to be from natural cycles. Mr Sallenger said there is no evidence to support that claim.