Greenland ice loss doubles in 10 years

Posted: 20 February 2006

Greenland's glaciers are melting faster than most experts thought, according to new research published in the journal Science. They are releasing almost twice as much ice into the Atlantic Ocean as they did five years ago, adding significantly to sea level rise, scientists report.

Ice melting into the Arctic Ocean. Photo: Peter West/National Science Foundation
Ice melting into the Arctic Ocean. Photo: Peter West/National Science Foundation
Ice melting into the Arctic Ocean. Photo © Peter West/National Science Foundation
The increases in glacier speed in the southern half of Greenland seem to be triggered by rising air temperature say the report's authors, who also question previous estimates of future melt which may have been too low.

"It takes a long time to build and melt an ice sheet, but glaciers react quickly to temperature change" said Dr Eric Rignot from the NASA Jet Propulsion Laboratory in Pasadena, California, who co-authored the report with Pannir Kanagaratnam from the University of Kansas.

The scientists tracked the speed of the glaciers from space, using satellite data gathered over the past 10 years. It was the first time that the changes in glacier velocity have been linked to estimates of the overall mass of ice being lost from almost the whole of Greenland.

Taking these speeds into account they calculate that Greenland contributes 0.5 mm per year to global sea level rise - out of an estimated total of 3mm. (If the whole of the Greenland ice sheet were to melt it would raise sea level by some 23 feet. But since it is almost as big as Mexico and 3kms deep, that could take a few hundred years.)

Disappearing ice

Air temperatures over Greenland have risen by three degrees Celsius over the past 20 years. And as the water has melted it has lubricated the interface between glaciers and the rocks below, speeding the glaciers march into the ocean, the authors say.

If the warming continues, the recent trend towards faster moving glaciers in southern Greenland may begin to effect those in the north as well, the scientists say.

But already the loss of ice from the Greenland ice sheet is startling. Putting together the findings from other research groups about the shrinking of glaciers with their own, and taking into the accumulation of ice from snowfall, the authors estimate that the overall annual loss of Greenland's ice sheet mass has more than doubled from 90 cubic kilometres a year in 1996 to 224 cubic kilometres per year in 2005.

Source: Science, a journal published by the American Association for the Advancement of Science, 17 February 2006.

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Greenland ice-sheet melting fast