For the first time since the beginning of the surveys, in 1978, the extent of the ice floating around the white continent passed below the 2 million km2 bar.
Le Monde with AFP
The Antarctic so far seemed better to resist climate change than the Arctic. But according to the observations of a group of researchers, the pack ice formed on part of the Austral Ocean reached, in February – which corresponds to the end of the summer in the southern hemisphere – its level the most Low for forty-four years and the beginning of the regular collection of information.
The natural cycle of the pack ice – the ice floats on the ocean – assumes that it bases the summer and refreshes the winter, satellites registering very precisely since 1978 the covered surfaces each season, of year by year. In the long term, the cast iron is fast in Greenland and the Arctic, but conversely, on the other side of the globe, in Antarctica, the trend was modestly upwards, despite significant annual and regional variations .
On February 25 this year, Antarctic packing was measured at 1.9 million square kilometers, a downward figure for the first time since the beginning of the surveys in 1978, reports the study of a group Researchers mainly from Sun Yat-sen in Canton in China, published on Tuesday, April 19, in an article in the magazine Advances in atmospheric sciences
A wave of unpublished heat
Five years after a previous record down to a little over 2 million km 2 in 2017, the area covered by the pack ice is therefore past for the first time under the 2 bar. million km 2 ; It is 30% less than the average calculated over three decades, between 1981 and 2010.
This study confirms the observations of the National Center 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, the disappearance of the banquisite was total to February 25th in the West of the Amundsen Sea and in eastern Ross Sea. More generally, she started to go back earlier in the year, from the beginning of September, and compared to 2017, she recorded late recovery at the end of February.
“Vicious circle”
The melting is bound to “thermodynamics”, that is to say to the influence of temperatures, but also to the movement of ice north, at least polar latitudes, and a layer of ice more Fine on the coast of the Amundsen Sea. Summer “anomalies” were observed mainly in the western part of Antarctica, more vulnerable to climate change than the larger area of Eastern Antarctica.
The melting has no impact on the sea level because the pack ice is formed by freezing salt water. But less coverage is also a source of concern.
When the white surface of the pack 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. “What in return melts more ice, and produces more heat absorption, in a vicious circle,” he describes.