Greenland ice sheet thinning rapidly

March 4, 1999
Web posted at: 10:24 p.m. EST (0324 GMT)

WASHINGTON (CNN) -- Glaciers along the southeastern coast of Greenland are thinning by more than 3 feet a year -- possibly because of global warming, according to a new study by NASA scientists.

Researchers compared aerial surveys of the Greenland ice sheet taken in 1993 and 1994 with a similar survey taken last year. Their data, reported in this week's edition of the journal Science, indicated that parts of the ice sheet near the ocean thinned at a rate of more than 3 feet (1 meter) per year.

While ice layers thickened by up to 10 inches (25 centimeters) in interior areas of Greenland during the same period, the net effect was a loss of ice mass for the whole area surveyed. The glaciers were also moving into the ocean at a higher rate, though that has so far had a negligible effect on global sea levels.

"Why (glaciers) are behaving like this is a mystery," said Bill Krabill, a researcher at NASA's Goddard Space Flight Center. "But it may indicate that the coastal margins of ice sheets are capable of responding quite rapidly to external changes, such as a warming climate."

Krabill said if the higher rate of ice flowing into the ocean from Greenland "accelerates or becomes more widespread, it would begin to have a detectable impact on sea level."

The glaciers may be speeding their flow to the ocean because melted ice on the surface is seeping to the bedrock, and the massive ice mountains are sliding on it, Krabill said.

Researchers believe the thinning is too dramatic to result from just increased surface ice melting or decreased snowfall.

Much of the Earth's water is contained in ice frozen around the North and South poles. Earlier studies have suggested that melting of this ice could cause massive coastal flooding as the sea level rises.

The Associated Press contributed to this report.