The annual maximum area of Antarctic sea ice has never been smaller

Europe 1 with AFP 08:16, September 26, 2023

Antarctica's sea ice has reached its maximum surface for the year, and it has never been so small since scientific surveys began, the U.S. reference observatory said Monday. Antarctic sea ice melts in summer and replenishes in winter. The latter is currently coming to an end in the southern hemisphere.

On September 10, "Antarctic sea ice reached an annual maximum extent of 16.96 million km2," wrote the National Snow and Ice Data Center (NSIDC). "This is the lowest maximum for sea ice in surveys from 1979 to 2023, by far." The maximum extent reached this year is 1.03 million km2 lower than the previous record, almost twice the area of the France.

A reformation of the sea ice at an unusually slow pace

In February, in the middle of the austral summer, the Antarctic sea ice had reached a low, with a minimum extent of 1.79 million square kilometers -- a melting record -- according to the NSIDC. Subsequently, the sea ice reformed at an unusually slow rate, despite the onset of winter.

In the Arctic, where summer ends, sea ice has also reached its lowest extent for the year, at 4.23 million km2, the NSIDC said. This is the sixth lowest in 45 years of data.

Should we see a link with global warming?

For several decades, Antarctica's sea ice had remained stable or even expanded slightly. But "since August 2016, the trend in the extent of Antarctic sea ice has taken a sharp downward turn, during almost every month" of the year, says the NSIDC. "The record for sea ice loss is shattered," said Walt Meier, a sea ice specialist at NSIDC. "Ice growth appears low across almost the entire continent and not in just one region."

The explanation is the subject of debate among scientists, who are reluctant to establish a formal link with global warming, as climate models have struggled in the past to predict the evolution of the Antarctic sea ice. But this trend since 2016 now appears "related to the warming of the upper layer of the ocean," writes the American observatory. "There is concern that this could be the beginning of a long-term trend of decline in Antarctic sea ice, as the oceans are warming globally."

Melting sea ice would cause catastrophic sea level rise

Melting sea ice has no immediate impact on sea level, as it is formed by freezing salt water already in the ocean. But the white sea ice reflects the sun's rays more than the darker ocean, and its loss thus accentuates global warming.

The loss of sea ice also exposes the Antarctic coasts to waves more, which could destabilize the ice sheet, which is made up of fresh water. Its melting would cause a catastrophic rise in sea levels. Melting Antarctic sea ice is already having a disastrous effect on wildlife, including emperor penguins, according to a study published in August in the scientific journal "Communications: Earth & Environment".

Out of five colonies of these monitored birds in the Bellingshausen Sea region, all but one suffered a "catastrophic" loss of 100% of chicks, which drowned or froze to death when the ice gave way under their tiny legs due to the early melting of the pack ice, which occurred in the middle of the breeding season. "We've been planning for it for some time, but to actually see it happen is grim," lead author Peter Fretwell, a researcher at the British Antarctic Survey, told AFP.