Melting of Greenland Raises Sea Level

W A S H I N G T O N, July 20 -- A warming climate is melting more than 50billion tons of water a year from the Greenland ice sheet, addingto a nine-inch global rise in sea level over the last century andincreasing the risk of coastal flooding around the world, a studyshows.

A NASA high-tech aerial survey shows that more than 11 cubicmiles of ice is disappearing from the Greenland ice sheet annually,says the study appearing Friday in the journal Science. That’sequal to about 1.25 trillion gallons and is enough to raise sealevel by a .13 millimeters a year.

“We see a significant trend [in loss of ice mass],” saidWilliam B. Krabill, an author of the study. “When we can goback after five years and see 10 meters of glacier gone, there issomething happening.”

Krabill, a NASA scientist and head of the ice sheet measurementproject, said the melting of Greenland ice and the calving oficebergs from Greenland glaciers is responsible for about 7 percentof the annual rise in global sea level.

Over the last century, measurements suggest sea level has risenabout nine inches, enough to cause some low-lying areas that wereonce high and dry to be awash at high tide or during storms. Thetrend could get worse, said Krabill, if the Greenland ice sheetcontinues its meltdown.

Rivers of Ice

“The margins of the Greenland ice sheet are undergoingsignificant thinning, in some places in excess of two meters ayear,” said Krabill.

Just how much ice is disappearing from Greenland and Antarctica,the world’s largest reservoirs of ice, has long been uncertain. TheNASA survey is the first to give a comprehensive measurement ofrecent changes in the Greenland ice sheet. Krabill said there is nosimilar data for Antarctica.

Krabill said the study shows glaciers on Greenland are movingmore rapidly to the sea, caused, perhaps, by melt water that coatsthe base of the glaciers and helps lubricate the downhill slide ofthe ice rivers.