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Measuring Greenland's ice loss

Margin of the ice sheet in West Greenland.
[Image courtesy of IMAU, Utrecht University]

Greenland has tons of ice. The Greenland ice sheet covers about 80 percent of the country, and it's the second largest ice sheet in the world, after the Antarctic ice sheet.

If this ice melts due to global warming, the water could have a major effect on sea level. Scientists want to predict how much sea level may rise in the future, since this information will be important for protecting coastal areas. But, they have had trouble figuring out how much the Greenland ice sheet is melting.

Front of Helheim Glacier.
[Image courtesy of Steve Morgan]

A new study should help. Michiel van den Broeke of Utrecht University in the Netherlands and his colleagues used two different methods to estimate Greenland's recent ice melting, and they got a good match, suggesting that their results are correct. One method used measurements of ice movement, plus some computer simulations of the ice sheet. The other used recent satellite measurements of the Greenland's gravity.

The researchers found that the Greenland ice sheet has lost about 1500 gigatons of mass, from 2000 to 2008, which represents a rate of sea level rise of about 0.46 millimeters per year, on average. The rate for the period 2006-2008 was much higher, though: about 0.75 millimeters per year.

The authors also determined that about half of the ice loss has probably occurred because of "surface processes," such as melting on the surface of the ice sheet, and the other half is likely due to "ice dynamics," such as the movement of the ice sheet toward the sea.


This research appears in the 13 November issue of the journal Science.