Antarctic sea ice at record low – knowledge

Sea ice around Antarctica reached an all-time low in early February. As the Alfred Wegener Institute announced, 2.2 million square kilometers in the Southern Ocean were still covered with ice on February 8, 70,000 square kilometers less than at the previous low point last year. Since satellite measurements began 40 years ago, so little sea ice has not been observed. With sea ice melting in Antarctica likely to continue into the second half of February, the bottom is likely to be even lower.

The ice cover around the Antarctic fluctuates significantly more over the course of the year than that in the Arctic. At the peak in September or October, between 18 and 20 million square kilometers of the sea surface around Antarctica are usually frozen. In the Antarctic summer, the ice then melts down to around three million square kilometers.

But this year, according to AWI measurements, the ice is melting extraordinarily quickly. As early as December there was exceptionally little sea ice in the Bellingshausen and Amundsen Seas off West Antarctica. The Bellingshausenmeer, where the AWI research ship is currently located North Star operated, is currently almost ice-free. Also in the long term, the sea ice in the Antarctic shows a decreasing trend of 2.6 percent per decade, measured in January.

Not only the air, but also the circumpolar deep water is getting warmer

“The rapid decrease in sea ice over the last six years is very astonishing because the ice cover had hardly changed in the previous 35 years,” Christian Haas, head of sea ice physics at AWI, is quoted as saying in a press release. It is unclear “whether this is the beginning of a rapid end to summer sea ice in Antarctica, or whether it is just a new phase of lower but still stable summer sea ice coverage.”

The researchers suspect that the cause of the current melt is above-average warm air temperatures west and east of the Antarctic Peninsula, which were most recently 1.5 degrees Celsius above the long-term average. In addition, a recurring climate pattern, the so-called “Southern Annular Mode” (SAM), influences wind circulation and ocean currents. As a result, more and more circumpolar deep water is currently rising in the direction of the continental shelf in the Antarctic, where it is driving sea ice melt.

Not only in West Antarctica, but also in the Pacific sector and in the Indian Ocean sector of Antarctica, there is currently noticeably little sea ice, which could also have something to do with the circumpolar deep water. This current flows around the entire Antarctic. According to a 2022 in the trade magazine NatureClimate Change published study The circumpolar deep water off East Antarctica has already warmed by 0.8 to 2 degrees Celsius compared to the mid-20th century. The scientists also attribute this to influences from the “Southern Annular Mode” – which in turn is amplified by man-made global warming.

How much the sea ice expands and shrinks has a very strong impact on the Antarctic ecosystem, such as the growth of phytoplankton. This feeds tiny crustaceans called krill, which are eaten by larger animals. If the timing of the plankton bloom shifts, this can disrupt the feeding of birds, fish, seals and whales.

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