The melting Arctic ice cap recovered slightly over the last winter, but scientists warned that it was still one of the worst years on record.
The twice yearly figures published by the National Snow and Ice Data Centre of the winter high and summer low for the Arctic sea ice is seen as a powerful indicator of global warming.
On Wednesday night the US organisation released the data for the winter of 2009-10 showing the maximum extent reached on March 31 was 15,25-million square kilometres. This was 650 000 square kilometres below the 1979 to 2000 average for March when measurements are taken for winter sea ice. The rate of decline for March over the 1978 to 2010 period is 2,6% per decade, according to NSIDC data. Arctic sea ice reflects sunlight, keeping the polar regions cool and moderating global climate.
Some recovery
NSIDC said there had been some recovery in the amount of ice that was two years old or more, from last year’s previous record low.
However, the spread of the ice, though higher than in some recent very bad years, was still low compared to past decades. “I think it’s the sixth or seventh lowest maximum out of the previous 32 years,” said Walt Meier, a research scientist at NSIDC.
Looking ahead to the other key annual figure — the lowest extent of sea ice at the end of the summer melting season — Meier said this year was also expected to be historically low, depending on temperatures and winds which blow the ice around, and sometimes out of the Arctic Sea into the warmer Atlantic and Pacific currents.
How low can it go?
“I would say [it’s going to be] low, perhaps one of the lowest, but not approaching 2007,” said Meier, referring to the record lows that year when the Arctic lost an area of ice the size of Alaska in one year. “Given the amount of thin ice we know we’re going to be low, it’s just a matter of how low.”