Antarctic sea ice recently reached its lowest concentration on record — falling below 2 million square kilometers (772,000 square miles) for the first time in 43 years of satellite observations.

“It’s the first time on satellite record that we’ve had sea ice extent fall below 2 million square kilometers. It’s a record and by quite a bit,” said Ryan Fogt, a climate scientist and an associate professor at Ohio University.

Sea ice builds and melts with the seasons. In Antarctica, sea ice typically reaches its maximum coverage at the end of the austral winter in mid- to late September and melts to its minimum extent in February.

The 2021-2022 melt-and-freeze cycle has been unusual, however. Antarctic sea ice reached its maximum extent Sept. 1, 2021, almost a month earlier than normal peak. The sea ice maximum extent, measuring 18.75 million square kilometers (7.24 million square miles), was also well above average. But it didn’t last long.

Antarctic sea ice peaked Sept. 1 at an above-average concentration. Rapid declines over spring and summer led to the continent’s lowest sea ice concentration in satellite record in February, however. (NOAA/NSIDC)

Sea ice retreated rapidly through austral spring and summer. In January and February, ice cleared out from the Ross, Amundsen and northwestern Weddell Sea regions. According to the National Snow and Ice Data Center (NSIDC), Antarctic sea ice reached its minimum extent of 1.92 million square kilometers (741,000 square miles) on Feb. 25. The previous low occurred in 2017, when sea ice extent reached 2.11 million square kilometers (815,000 square miles).