By historical temperatures and a record cast. Antarctic sea ice reached its lowest level in 44 years at the end of the Australian summer in February, according to observations by a group of researchers published Tuesday, when Antarctica appeared to be more resilient to climate change than the Arctic so far.
The natural cycle of pack ice (the ice that floats on the ocean) is that it melts in summer and re-forms in winter, with satellites recording very accurately from year to year since 1978 the areas covered in each season . In the long run, melting is rapid in Greenland and the Arctic, but conversely, in Antarctica, the trend increased modestly, despite significant annual and regional variations.
This year, the Antarctic sea ice sank and was measured on February 25 at 1.9 million square kilometers, a record low since the measurements began in 1978, a group of researchers, mainly from Sun University, reported. published in the journal Advances in Atmospheric Sciences.
30% reduction from the average
Five years after an earlier record low of just over 2 million km2 in 2017, the area covered by sea ice has fallen below 2 million km2 for the first time. That is 30% less than the three-decade average between 1981 and 2010.
This study confirms observations by the US 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 Tuesday, the pack ice disappearance in the western Amundsen Sea and in the eastern Ross Sea was complete by February 25. More broadly, sea ice started to retreat earlier in the year, starting in early September, and showed a late recovery in late February compared to 2017.
Vicious circle
The melting is linked to “thermodynamics”, ie the influence of temperatures, but also to the movement of ice northwards, to less polar latitudes, and with a thinner ice cover on the coast of the Amundsen Sea. The summer “anomalies” have been observed mainly in the western part of Antarctica, which is more vulnerable to climate change than the greater East Antarctica area.
The melting of sea ice does not affect sea levels because sea ice is formed by the freezing of salt water. But less coverage is also a concern.
When the white surface of the sea ice, which reflects the sun’s energy, 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.
