Historic temperatures and record melting.
The Antarctic sea ice reached its lowest level in 44 years at the end of the austral summer in February, according to observations by a group of researchers published on Tuesday, when Antarctica seemed to resist better so far. to climate change than the Arctic.
The natural cycle of the pack ice (the ice that floats on the ocean) is that it melts in summer and re-forms in winter, with satellites recording very precisely since 1978 the areas covered in each season, from year to year. .
In the long term, melting is rapid in Greenland and the Arctic, but conversely, in Antarctica, the trend was modestly increasing, despite significant annual and regional variations.
This year, the Antarctic sea ice has therefore plunged and was measured at 1.9 million square kilometers on February 25, a record low since records began in 1978, reports a group of researchers mainly from Sun University. Yat-sen in Canton, in an article published in the journal Advances in Atmospheric Sciences.
30% reduction from the average
Five years after a previous record low of just over 2 million km2 in 2017, the area covered by sea ice has dropped below 2 million km2 for the first time.
That is 30% less than the average over three decades between 1981 and 2010.
This study confirms the observations of the American National Snow and Ice Data Center announced a few weeks ago, just before the arrival of an unprecedented heat wave in eastern Antarctica in March.
According to the authors of the study published on Tuesday, in the western Amundsen Sea and in the eastern Ross Sea, the disappearance of the pack ice was complete by February 25.
More generally, the sea ice began to retreat earlier in the year, from the beginning of September, and compared to 2017, it recorded a late recovery, at the end of February.
Vicious circle
The melting is linked to "thermodynamics", i.e. the influence of temperatures, but also to the movement of ice to the north, to less polar latitudes, and to a thinner layer of ice on the coast. of the Amundsen Sea.
The summertime " anomalies " have been observed mainly in the western part of Antarctica, which is more vulnerable to climate change than the larger area of East Antarctica.
The melting of sea ice has no impact on sea level, because sea ice is formed by the freezing of salt water.
But less coverage is also cause for concern.
When the white surface of the sea ice, which reflects the energy of the sun, is replaced by the dark surface of the sea, "there is less heat reflection and more absorption", explains Qinghua Yang, one of the co-authors, professor at Sun Yat-sen University.
“Which in turn melts more ice, and produces more heat absorption, in a vicious circle,” he describes.
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