Arctic sea ice cover second lowest since 1979: data centre

Arctic sea ice extent for December 2017 was 11.75 million sq km. The magenta line shows the 1981 to 2010 average extent for that month. (IMAGE COURTESY OF THE NSIDC)

Since 1979, Arctic sea ice extent has almost never been as low as it was in December—and it started off January with the lowest extent yet observed in the satellite record for this time of year.

The National Snow and Ice Data Center reported Jan. 3 that Arctic sea ice extent for December 2017 averaged 11.75 million square kilometres—the second lowest in the 1979 to 2017 satellite record for that month.

December’s sea ice extent was 1.09 million square kilometres below the 1981 to 2010 average and 280,000 square kilometres above the record low December extent recorded in 2016, the Colorado-based organization said.

Last month, sea ice cover was below average in the far northern Atlantic and the Bering Sea, while “notably high temperatures prevailed over most of the Arctic, especially over Central Alaska,” the NSIDC said in its year-end roundup.

Arctic sea ice growth during December 2017 averaged 59,800 sq km per day, not far off the average rate,

But its extent remained on a downward trajectory: the linear rate of sea ice loss for December came in at 47,400 sq km per year or 3.7 per cent per decade, the NSIDC said.

Assessments of sea-ice thickness also suggest that Arctic sea ice was “very low in overall volume.”

December air temperatures at 760 metres above the Arctic Ocean were two to six degrees Celsius above average, similar to the warmer air temperature pattern seen in November.

The above-average pattern was driven in part by “the arrangement of high and low air pressure regions surrounding the Arctic,” the NSIDC said.

In December, the annual update on how the Arctic is faring environmentally, released by the United States National Oceanic and Atmospheric Administration, said you have to look back more than 1,500 years—“and likely longer than that”—to find such a rapid and large-scale mix of sea ice decline and warming temperatures in the Arctic.

On Jan. 5, last year was also determined by scientists to be the second warmest year on record, almost 0.1 C warmer than 2015 and 0.5 C warmer than the average between 1981 and 2010.