26/3/10

ARCTIC ARCH DECLINE



EUROPEAN SPACE AGENCY

NATURE


Nature Reports Climate Change
Published online: 18 March 2010 | doi:10.1038/climate.2010.21


Each winter and spring, large ice blockages known as arches form along the straits leading out of the Arctic Ocean, preventing sea ice from drifting further afield. Scientists now report that in 2007 ice arches did not form along one of these passages, known as the Nares Strait, and that this contributed to record low sea ice cover in the Arctic that year.
Ron Kwok of the Jet Propulsion Laboratory in Pasadena, California, and colleagues used satellite imagery to track the movement of sea ice through the Nares Strait, the passageway that separates Greenland from Ellesmere Island, from 1997 to 2009. The Nares Strait carries only ten per cent of the ice lost to the Atlantic each year, but it drains the oldest and thickest ice. They found that during typical winters and springs, ice arches develop at two key locations along the strait. Failure of these arches to form in 2007, however, meant that transport through the strait that year was more than twice the average over the 13-year study period.
The team warns that future warming in the Arctic could inhibit arch formation, allowing more sea ice to escape and enhancing the decline of summer sea ice cover.


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