The surface of the Antarctic ice shelf, which is at its maximum this season, is this year the lowest ever recorded since scientific surveys began, the leading American observatory announced on Monday September 24.
The Antarctic sea ice melts in summer and replenishes in winter, which is currently coming to an end in the Southern Hemisphere. On September 10, “Antarctic sea ice reached a maximum annual extent of 16.96 million km2,” writes the National Snow and Ice Data Center (NSIDC). “This is the lowest maximum for sea ice in records from 1979 to 2023; and by far. »
The maximum extent reached this year is 1.03 million km² smaller than the lowest previously recorded, or almost twice the area of ??France.
In February, in the middle of the austral summer, the Antarctic sea ice had reached its lowest surface area, with a minimum extent of 1.79 million km², a melting record, according to the NSIDC. Subsequently, it reformed at an unusually slow pace, despite the arrival of winter.
In the Arctic, where summer is ending, the sea ice has also reached its smallest extent for the year, with 4.23 million km². This is the sixth “lowest” since records began forty-five years ago.
“Sharp turn”
For several decades, the surface area of ??the Antarctic sea ice had remained stable or expanded slightly, but “since August 2016, the trend in the extent of the Antarctic sea ice has taken a sharp downward turn, during almost every month” of the year, the NSIDC points out.
The explanation is debated among scientists, who are hesitant to establish a formal link with global warming, as climate models have struggled in the past to predict changes in the Antarctic sea ice.
Since 2016, the trend now seems “linked to the warming of the upper layer of the ocean,” writes the American observatory. “There is concern that this could be the start of a long-term trend of decline in Antarctic sea ice as oceans warm globally. »
The melting has no immediate consequences on sea level, as it is sea water, but the whiteness of the ice floe reflects the Sun’s rays more than the ocean does, darker, and its reduction therefore accentuates global warming. In addition, it further exposes the coasts of Antarctica to waves, which could destabilize the ice sheet, made up of fresh water. Its melting would therefore cause a catastrophic rise in water levels.
