Arctic sea ice at low levels, still melting

Sea ice cover in the Arctic was at its third-lowest ever this past month, and unusually clear weather and warm winds are continuing to promote ice melt, according to the US National Snow and Ice Data Centre.

It remains to be seen whether this year’s ice extent will set a new record low, as the melt season doesn’t end until September.

Satellite images show that July Arctic sea ice melt was nearly identical to that of July 2007. Sea ice extent last month totalled about 8.81 million square kilometres, just 680,000 square kilometres above the record low of July 2007 and 250,000 square kilometres less than ice cover than in July 2008. Last month’s ice cover also measured some 1.29 million square kilometres below the 1979 to 2000 average.

Sea ice extent is unusually low in the Kara Sea, Baffin Bay, and along the Russian coast. The only area with significant above-average ice extent is southern Hudson Bay.

The Arctic atmospheric circulation pattern this summer has been similar to that seen in the summer of 2007. As in 2007, an unusually strong high-pressure cell settled over the Beaufort Sea, bringing warm air into the Chukchi Sea. This year, the Beaufort Sea anticyclone, averaged for June and July 2009, was even stronger than the anticyclone in 2007. However, unlike 2007, this year the Beaufort Sea high-pressure cell is not paired with unusually low pressure over eastern Siberia, the “dipole” pattern that in 2007 promoted strong surface winds and extreme melt.