Post by Andrei Tchentchik on Mar 6, 2020 17:42:42 GMT 2
(.#A.067).- Calotte Antartique, a record melting rate was reached on Dec. 24. 2019.
Calotte Antartique, a record melting rate was reached on Dec. 24. 2019.
By: Damien Altendorf, scientific writer
December 31, 2019, 12:22 p.m.
Credits : EOSDIS Worldview.
The summer of 2019-2020 has started with a fanfare in the southern hemisphere. While Australia and New Zealand have recently redefined many heat records, Antarctica has experienced an exceptional thaw episode. Events that carry a strong symbol at a time when climate change has become a major societal concern.
On December 24, as the world was celebrating Christmas Eve, 15% of the surface of the southern polar cap was melting. This is a record every month since we have adapted monitoring. In other words, since 1979. In general, seasonal melting has been abnormally active since mid-November. Indeed, the curve in red in the figure below is systematically well above the average.
Percentage of the Antarctic ice cap subject to surface melting. The red curve represents the 2019-2020 season. The black curve represents the 1981-2010 average and the gray range, the first standard deviation. Finally, the blue dotted lines indicate the high and low records before 2019.
Credits: climato.be/.
Note that the data presented are preliminary and result from forced modeling by the available observations. The interest being to provide a first estimate (a first-guess, in English). However, they undoubtedly show that something abnormal happened around the Christmas holidays. To give an idea, it is an area equivalent to that of Denmark which suffered a thaw this December 24.
Moreover, it appears that the melting season has so far been exceptional. A characteristic that can be attributed to the very brutal weakening of the polar stratospheric vortex during last spring. An event which occurs naturally every year but which was also there of record intensity.
"A weaker polar vortex makes it easier for soft air masses to reach the ice cap (which is usually protected by its polar vortex as it was the previous summer). The fact that the extent of the sea ice is very small also increases the possibility that the fresh air masses reach the cap, "explains Xavier Fettweis, climatologist at the University of Liège in Belgium.
Towards an acceleration of surface melting
If the origin of the anomaly discussed has obvious meteorological causes, it is placed in a strong context which is that of a global warming of the atmosphere and the ocean. Also, scientists expect this type of episode to become more frequent and more intense in the future.
Anomaly in the number of thaw days between November 1 and December 30, 2019.
Credits: climato.be/.
It will be recalled in passing that for several decades, the Antarctic ice cap has been losing mass at an accelerated rate. In particular due to the weakening of the ice platforms surrounding the continent. Process following the warming of the ocean. But the contribution of surface cast iron is taking on increasing proportions. However, in addition to directly increasing losses, the latter has a propensity to create crevices in the ice. Thus, the risk of fracturing of the platforms is amplified.
“[The ice platforms are] a bit like a cork. They hold a lot of ice in Antarctica, "said Robin Bell, geophysicist at the Lamont-Doherty Earth Observator at Columbia University. When they are weakened "it means you are pumping more ice into the ocean, and that is what matters to sea level".
F I N .
Calotte Antartique, a record melting rate was reached on Dec. 24. 2019.
By: Damien Altendorf, scientific writer
December 31, 2019, 12:22 p.m.
Credits : EOSDIS Worldview.
The summer of 2019-2020 has started with a fanfare in the southern hemisphere. While Australia and New Zealand have recently redefined many heat records, Antarctica has experienced an exceptional thaw episode. Events that carry a strong symbol at a time when climate change has become a major societal concern.
On December 24, as the world was celebrating Christmas Eve, 15% of the surface of the southern polar cap was melting. This is a record every month since we have adapted monitoring. In other words, since 1979. In general, seasonal melting has been abnormally active since mid-November. Indeed, the curve in red in the figure below is systematically well above the average.
Percentage of the Antarctic ice cap subject to surface melting. The red curve represents the 2019-2020 season. The black curve represents the 1981-2010 average and the gray range, the first standard deviation. Finally, the blue dotted lines indicate the high and low records before 2019.
Credits: climato.be/.
Note that the data presented are preliminary and result from forced modeling by the available observations. The interest being to provide a first estimate (a first-guess, in English). However, they undoubtedly show that something abnormal happened around the Christmas holidays. To give an idea, it is an area equivalent to that of Denmark which suffered a thaw this December 24.
Moreover, it appears that the melting season has so far been exceptional. A characteristic that can be attributed to the very brutal weakening of the polar stratospheric vortex during last spring. An event which occurs naturally every year but which was also there of record intensity.
"A weaker polar vortex makes it easier for soft air masses to reach the ice cap (which is usually protected by its polar vortex as it was the previous summer). The fact that the extent of the sea ice is very small also increases the possibility that the fresh air masses reach the cap, "explains Xavier Fettweis, climatologist at the University of Liège in Belgium.
Towards an acceleration of surface melting
If the origin of the anomaly discussed has obvious meteorological causes, it is placed in a strong context which is that of a global warming of the atmosphere and the ocean. Also, scientists expect this type of episode to become more frequent and more intense in the future.
Anomaly in the number of thaw days between November 1 and December 30, 2019.
Credits: climato.be/.
It will be recalled in passing that for several decades, the Antarctic ice cap has been losing mass at an accelerated rate. In particular due to the weakening of the ice platforms surrounding the continent. Process following the warming of the ocean. But the contribution of surface cast iron is taking on increasing proportions. However, in addition to directly increasing losses, the latter has a propensity to create crevices in the ice. Thus, the risk of fracturing of the platforms is amplified.
“[The ice platforms are] a bit like a cork. They hold a lot of ice in Antarctica, "said Robin Bell, geophysicist at the Lamont-Doherty Earth Observator at Columbia University. When they are weakened "it means you are pumping more ice into the ocean, and that is what matters to sea level".
F I N .
