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Arctic winter sea ice in 2021 joint seventh-lowest on record, finds NASA

The sea ice maximum in 2021 is not close to a record, but still quite low compared to any year prior to 2000, according to lead author of the study

Sea ice in the Arctic has reached its maximum extent for 2021 — tying with 2007’s as the seventh-smallest extent of winter sea ice. This may mean that the Arctic is losing more ice than it can recover. 

The ice peaked at 14.77 million square kilometres (km2) on March 21, according to scientists at the National Aeronautics and Space Administration (NASA)-supported National Snow and Ice Data Center (NSIDC).

The NSIDC has termed the development as “uneventful maximum”. It, however, noted it followed an “exceptional” year for sea ice: Arctic’s summer minimum in September 2020 was the second-lowest on record.

This year’s maximum was 870,000 km2 below the 1981-2010 average maximum and 360,000 km2 above the lowest maximum recorded in 2017, NSIDC noted.

Arctic sea ice extent as of March 29, 2020 for the 2020-21 summer (blue line), along with daily ice extent data for the four previous years: 2011-2012 (green) and the 1981-2010 median (dark grey) and the grey shading shows the range around the median. Credit: NSIDC

The ice extent in the Arctic changes throughout the year: It grows during the winter before reaching its peak in February or March. It then melts throughout the spring and summer towards its annual minimum, which is typically in September.

Carbon Brief quoted Ted Scambos, senior research scientist at NSIDC, as saying:

“The sea ice maximum in 2021 is not close to a record, but still quite low compared to any year prior to 2000.”

The low ice extent, according to NSIDC, was because of the positive phase of the phenomenon called Arctic Oscillation. During this phase, a ring of strong winds circulating around the North Pole acts to confine colder air across polar regions.

This pattern transported ice from the Siberian coast, across the pole and out of the Arctic Ocean, leaving thinner ice along the Siberian coast which was more prone to melting.

Average Arctic sea ice extent over the summer minimum for each decade of the satellite era (dotted lines) and for 2020 (red line). Individual years also shown. Chart by Zack Labe using data from the Japan Aerospace Exploration Agency

According to NSIDC:

From 13 October into early November, the daily sea ice extent was the lowest for that day in the satellite record. The low sea ice extent left vast expanses of open water across the Arctic throughout November, which lost heat to the atmosphere and caused hotspots to form near the surface of the ocean. 

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