Thicker, older ice disappearing

Arctic ice continues to shrink and thin


Arctic sea ice continues to shrink and thin, say two major U.S. agencies.

The bad news came from The National Aeronautics and Space Administration and the National Snow and Ice Data Centre.

Scientists who track Arctic sea ice cover from space announced April 6 that this past winter had the fifth lowest ice cover on record.

Researchers said the sea ice cover during March 2009 averaged 15.16 million square kilometers. That's 590,000 square km below the 1979 to 2000 average.

"Ice extent is an important measure of the health of the Arctic, but it only gives us a two-dimensional view of the ice cover," said Walter Meier, research scientist at the centre and the University of Colorado. "Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover. As the ice cover in the Arctic grows thinner, it grows more vulnerable to melting in the summer."

New evidence from satellite observations shows Arctic sea ice is thinning as well.

Thinner ice that melts and re-freezes every year, now makes up about 70 per cent of the Arctic sea ice in winter, up from 40 to 50 per cent in the 1980s and 1990s.

Thicker ice, which is two or more years old, now makes up just 10 per cent of winter ice cover.

Overall, it was a fairly warm winter in the Arctic.

Air temperatures over the Arctic Ocean were an average of 1° C to 2° C above normal. This warmth probably stemmed from unusually low sea ice in the region throughout much of the winter, which allowed the ocean to pump heat into the atmosphere, the NSIDC said.

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