At a Glance

Land is sinking along the mid-Atlantic coast because of land subsidence dating from the ice age.This will make the rate of human-caused sea level rise twice the global average in the decades to come.

Land is sinking along the mid-Atlantic coast, which will make the rate of human-caused sea level rise twice the global average in the decades to come for cities and towns that call the region home, a recent study says.

The from the Arctic between 20,000 and 95,000 years ago during the last ice age, researchers noted in their study published late last year in the journal Nature. Ahead of the massive ice sheet, land was also pushed into what scientists call a "glacial forebulge."

As the ice melted, the land began to settle, or subside, and continues to settle in region. The subsidence makes the rate of sea level rise much greater than along other coastlines.

“In New England, there is not too much additional from land motion because it’s near the hinge point,” Peter Huybers, co-author of the study and professor of earth and planetary sciences at Harvard University, said in a press release. “The bulge caused by the ice sheet was centered on the mid-Atlantic, and because it’s still settling down, the relative rise of sea level in the mid-Atlantic is about twice the global average.”

The scientists, who used "everything from tide gauges to GPS data to paint the most accurate picture of sea-level rise along the east coast," say cities and towns that call the mid-Atlantic coast home will need to prepare not only for human-caused sea level rise but for the increased rate cause by natural subsidence of the land.

“The fact that the mid-Atlantic is subsiding because of long-term geologic processes means that it will continue for centuries and millennia, in addition to whatever other changes in sea level occur,” Huybers said. “The mid-Atlantic is already having to cope with routine coastal flooding, and this problem is only going to get worse with time.

The Hampton Roads area at the mouth of the Chesapeake Bay is particularly vulnerable to king tides and coastal flooding. A network of GPS stations, operated by the National Geodetic Survey, has tracked the for several decades, the Chesapeake Quarterly reports.

Researchers using the data collected estimate that the land around the bay is falling by about 1.5 millimeters per year. The Hampton Roads area appears to be falling faster, at a rate of 4 millimeters per year.

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Other studies have suggested the subsiding in the region, particularly in around the Chesapeake Bay, is also a result of human activities.

A report released by the U.S. Geological Survey in 2013 determined and other users is exacerbating the land subsidence.

In the report, USGS hydrologist Jack Eggleston and his colleague, Jason Pope, found that areas where land is subsiding the fastest in the Chesapeake Bay area coincides with the greatest amount of groundwater pumped from the ground. In fact, Eggleston and Pope estimate the groundwater withdrawal accounted for about half of the subsidence during the last several decades.

"Causes of subsidence that are most relevant to the southern Chesapeake Bay region include aquifer-system compaction caused by groundwater withdrawals and glacial isostatic adjustment," the scientists wrote in the report.