Arctic sea ice reached another record last month, posting the lowest average February extent since satellite records began in 1979, scientists said on Wednesday.
Sea ice extent -- defined as the area where ice covers at least 15 percent of the sea surface -- averaged 5.48 million square miles over the month, about 7.7 percent lower than the average long-term February extent measured from 1981 to 2010, the National Snow and Ice Data Center said in its monthly report.
The February record follows January's record-low monthly ice extent.
Sea ice usually begins to form in late September and peaks in early or mid-March before the annual melt season starts.
But this year, the growth has been slower than in the past, with a notable nearly two-week stall in mid-February. The ice rebounded a bit late in the month, largely thanks to a growth spurt in Russia's Sea of Okhotsk, but was still much lower than normal at the start of March. The late ice is low in concentration, according to NSIDC data, and expected to disappear quickly once the melt season starts.
The February stall is part of a wider trend of reduced sea-ice extent in winter, a season that once saw nearly all marine waters in the Arctic frozen over. Last year's annual maximum of 5.61 million square miles, reached on Feb. 25, 2015, was the lowest maximum on record.
Unusual warmth across the Arctic is blamed for the slow ice growth this winter, the NSIDC said in its report. It cited satellite data from NASA that found average February air temperatures over the Beaufort Sea, Chukchi Sea and central Arctic Ocean were about 9 degrees higher than the 2003-2015 average. Warmth was especially notable near the North Pole, the center said. February temperatures over the central Arctic Ocean were 11 to 14 degrees above 1981-2010 average for the month, the center said.
Winter ice freezeup was late, lagging by a full two months in the Kara and Barents seas, the center said. Ice also formed late in other parts of the Arctic -- the Beaufort, Chukchi, East Siberian and Laptev seas -- between 10 and 40 days later than the average, the center said.