Thinning Glaciers

NASA Researchers Document Shrinking of Greeland’s Glaciers
Release: 99-33, March 4, 1999

Greenland's southeastern glaciers are rapidly thinning and their lower elevations may be particularly sensitive to potential climate changes, a NASA study suggests. "The results of this study are important in that they could represent the first indication of an increase in the speed of outlet glaciers," said Bill Krabill, principal investigator at NASA Goddard Space Flight Center's Wallops Flight Facility, Wallops Island, VA. An outlet glacier acts as a major ice drainage region for an ice sheet. "The excess volume of ice transported by these glaciers 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," Krabill said.

In the March 5 issue of Science, researchers report the glacial thinning is too large to have resulted from increased ice-surface melting or decreased snowfall. The researchers believe the thinning, as much as 30 feet over five years in some locations, is the result of increasing discharge speeds of glaciers flowing into the Atlantic Ocean. Krabill said surface-melt water might be seeping to the bottom of glaciers. Such seepage may be reducing the friction between the ice and the rock below it, enabling the glaciers to slide with less friction across the bedrock and thus allow more ice to slip off into the ocean, according to Krabill. "The results of this study are significant because they provide the first evidence of widespread thinning of low-elevation parts of one of the great polar ice sheets. The results also suggest that the thinning outlet glaciers must be flowing faster than necessary to remove the annual accumulation of snow within their basins," said Krabill. "Why they are behaving like this is a mystery," said Krabill.