Scientists monitoring the Arctic ice cap report an increase in the amount of sea ice that is two years old or more in the region, but they are also warning that the spread of ice is still low compared with the amount seen in past decades.

Walt Meier, a research scientist at the National Snow and Ice Data Centre (NSIDC), at the University of Colorado, said of the region's sea ice: “I think it's the sixth or seventh lowest maximum of the previous 32 years.” The NSIDC released data on Tuesday for the winter of 2009-10, which showed that the maximum extent of ice by March 31 this year was 15.2m square kilometres. This was 647,000 square kilometres below the 1979-2000 average for March, the month when measurements are taken for winter sea ice.

The twice-yearly figures published by NSIDC of the winter highs and summer lows for Arctic sea ice are seen as a strong indicator of global warming. The sea ice reflects sunlight, keeping the polar regions cool and moderating global climate. The rate of decline for the March months, over the 1979 to 2010 period, was 2.6 per cent a decade.

Meier predicted that this year's summer melting season would also show historically low amounts. The quantity would depend, though, on both temperature and the winds which sometimes take the ice out of the Arctic Sea into the warmer Atlantic and Pacific currents.

“I would say [it's going to be] low, perhaps one of the lowest, but not approaching 2007,” said Meier, referring to the record dip in that year when the Arctic lost an area of ice the size of Alaska. “Given the amount of thin ice, we know we're going to be low, it's just a matter of how low.” — © Guardian Newspapers Limited, 2010