A study by Nasa scientistshas found that the southeastern glaciers of Greenland have thinned by as much as 10 metres (33 feet) over five years.
The researchers believe that the shrinking is likely to be the result of an increase in the rate at which the ice at the bottom of the glaciers is melting into the Atlantic Ocean.
"This has had a negligible effect on global sea level thus far, but if it accelerates or becomes more widespread, it would begin to have a detectable impact on sea level," said Bill Krabill, principal investigator at Nasa's Goddard Space Flight Center, Virginia.
Nasa measured the thickness of the entire ice sheet of Greenland using a laser altimeter mounted on board an aircraft flown at 400 metres above the surface. The result of the survey, published today in the journal Science, showed three areas where ice was thickening due to snowfall but much larger areas where significant thinning had occurred.
In the areas of thinning, the scientists reported warmer than normal temperatures for the period 1993 to 1998, but they also observed thinning on the west coast where the temperatures were cooler than normal.
"This study provides the first evidence of widespread thinning of low- elevation parts of one of the great polar ice sheets," Dr Krabill said. "Why [the glaciers] are behaving like this is a mystery, but it might indicate that the coastal margins of ice sheets are capable of responding quite rapidly to external changes, such aswarming of the climate."