Water and Ice

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Science  09 May 2008:
Vol. 320, Issue 5877, pp. 713a
DOI: 10.1126/science.320.5877.713a
CREDIT: SARAH B. DAS

The water at the base of glacial ice sheets lubricates the ice-earth interface, allowing the ice sheet to slide more quickly and easily over the ground below, but its role in how glaciers lose mass is unclear. How will ice-sheet mass loss be affected by climate warming? Das et al. (p. 778, published online 17 April) describe the disappearance of a large supraglacial lake in Greenland, which occurred with startling speed in the summer of 2006, when a torrent of water emptied into the kilometer-thick ice sheet below it at an average rate of flow greater than that of Niagara Falls. Taking a wider perspective, Joughin et al. (p.781, published online 17 April) synthesize a wide array of data on ice motion from across Greenland to show how the ice sheet responds to surface melting and suggest that surface melting will probably cause a clear, but not catastrophic, increase in mass loss from the Greenland Ice Sheet in the foreseeable future.

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