January Arctic sea ice extent lowest ever

The extent of the Arctic sea ice cover is the lowest seen in January since satellite ice observations began in 1979, the National Snow and Ice Data Center has reported. The average extent of 13.53 million square miles observed this January was 35,000 square miles less than the previous record low, recorded for January 2011. This year’s observation places the measured ice extent in a continuing trend of January ice extent loss at a rate of 3.2 percent per decade.

NSIDC says that this year’s especially low area of ice in January is largely attributable to low ice coverage in the Barents Sea, the Kara Sea and the East Greenland Sea, and to below average conditions in the Bering Sea and the Sea of Okhotsk. There was also less ice than usual in the Gulf of St. Lawrence. On the other hand, ice conditions were near average in Baffin Bay, the Labrador Sea and Hudson Bay.

January 2015 was a remarkably warm month, with air temperatures more than 13 F above average across much of the Arctic Ocean, NSIDC says. It appears that these unusually high temperatures relate to a climatic feature called the Arctic oscillation, which turned strongly negative around mid-January. The negative phase of this phenomenon, which relates to the variation over time of the distribution of air pressures at low altitudes, results in especially high atmospheric pressures in the Arctic and the lodging of warmer than normal air in the region.

Interestingly, although the sea ice extent for the Arctic as a whole has been consistently shrinking, from 2005 until this year the winter sea ice cover in the North Atlantic region of the Arctic had actually been growing somewhat, NSIDC says. Recent research suggests that this phenomenon may be related to variability in the circulation of water in the Atlantic and the consequent movement of warm water north from the equator.

- ALAN BAILEY