Monday, July 27, 2009

Study examines feedback mechanism that may be hastening Greenland ice-sheet melt

Kate Ravilious in Environmental Research Web: The Greenland ice sheet and the surrounding Arctic sea ice have experienced record levels of melting in recent years. But are the two linked? When sea ice melts does it encourage the ice sheet to melt too? A new study suggests that the answer to this question may be yes.

Satellite measurements show that the area of the Greenland ice sheet that experiences melting has increased by around 16% over the last 30 years. Meanwhile, Arctic sea-ice extent shrunk to a record minimum in the summer of 2007; 39% less than the long-term average. The years of 2008 and 2005 were also extreme; on average the summer sea-ice extent has been decreasing at more than 10% per decade for the last 30 years.

…Asa Rennermalm from the University of California in Los Angeles, US, and her colleagues have been investigating one potential feedback mechanism that may be hastening ice-sheet melt. Using satellite data gathered over the last 30 years, they looked at the way that the Greenland ice sheet and surrounding sea ice have changed in size over time.

They found a strong covariance between sea-ice extent and Greenland ice-sheet melt, particularly in the late summer of each year. The smaller the sea ice extent, the greater the rate of melting of the ice sheet. "They appear to work in concert," Rennermalm told environmentalresearchweb. Not all regions of the ice sheet showed this covariance, but where it did occur – in the west and the southwest – it was very strong…

The edge of the Greenland ice sheet, by the incomparable Hannes Grobe of the Alfred Wegener Institute for Polar and Marine Research, under the Creative Commons Attribution ShareAlike 2.5 License

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