Arctic sea ice, nearing the time of year when it reaching its peak freeze, is at the lowest winter extent in the satellite record, and a fourth consecutive record-low winter maximum might be set in coming days.
Average February ice extent was 13.95 million square kilometers (5.39 million square miles), the lowest for that month since satellite records began in 1979 and nearly 9 percent below the 1981-to-2010 February average, the National Snow and Ice Data Center reported on Tuesday.
After months of unusually warm winter weather — which follows previous winters also punctuated by unusual warm spells — conditions were setting up for a maximum extent even lower than the record set last year, said NSIDC director Mark Serreze. But even though extent had trended down in the days before Tuesday, he was not yet declaring a new record.
“It’s too early to call the maximum. It could be any day,” he said. There could also be a late freeze-up that prevents 2018 from being a record-low maximum, he added. “But it’ll be thin stuff.”
The recent trend toward lower winter sea ice has become noticeable, Serreze said.
In the past, the diminishing sea-ice minimums measured in September got most of scientists’ attention, but now the trend toward late winter freeze-up, smaller ice coverage and occasional winter melting is being seen as significant, he said.
This winter, as in past winters, there were heat waves carried into the atmosphere over the Arctic Ocean, he said. That included a late-February heat wave that drove temperatures near Alaska’s North Slope above freezing, he said.
“They’re crazy, crazy stuff,” he said. “They’re all related to the record-low sea ice maximum.”
Exactly how the Arctic is getting warm in winter is not yet understood, he said. The “proximal explanation” is that the jet stream is skewed, but the mechanics of that jet-stream change is still being investigated, he said.
There have been noticeable regional trends in Arctic sea ice development this winter, too.
Ice has been especially scarce in the Bering Sea throughout the winter, the NSIDC reported. Sea ice declined there during the first three weeks of February, leaving the eastern Bering Sea largely ice-free for most of the month and creating a spot of open water that extended north through the Bering Strait, the NSIDC reported. Barents Sea in February continued its winter-long low sea ice, and by the end of the month an ice-free area of water had opened north of Svalbard, the NSIDC said.
Freeze-up, though relatively early in much of the central Arctic Ocean, was extremely late at lower latitudes, the NSIDC said. In the Chukchi Sea and Bering Sea on the Pacific side and the Barents Sea and East Greenland Sea on the Atlantic side, freeze-up was more than a month later than normal and occurred after January, the NSIDC said. The ice that formed in those areas was thin, the center said.
A study published last year in Geophysical Research Letters found that warming events in the Arctic are on the rise, the NSIDC noted.
Yereth Rosen is a 2018 Alicia Patterson Foundation fellow.