NASA data show thinning Arctic ice

Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thick, older ice shrinking by the equivalent of Alaska's land area, Agence France-Presse reported, citing a study using data from a NASA satellite. The Ice, Cloud and Land Satellite (ICESat) allows scientists to measure changes in the thickness and volume of the ice, rather than only measurements of area.

Scientists from the US space agency and the University of Washington in Seattle estimated both the thickness and volume of the ice cover in the Arctic Ocean. They found that it thinned about 17 centimetres a year, or 67 centimetres over four winters, according to research published in the Journal of Geophysical Research-Oceans.

Thicker, older ice that survived one or more summers shrank by 42% in the same time period, they said – by 1.5 million square kilometres, or almost the size of Alaska’s land area.

In recent years, the amount of ice that forms in the winter has not been sufficient to offset losses in summer, the ICESat study showed. More open water in summer then absorbs more heat, warming the ocean and further melting the ice, the scientists said. The researchers attributed the changes in the overall thickness and volume of Arctic sea ice to recent warming and anomalies in patterns of sea-ice circulation.

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