Causes of the record-low Antarctic sea-ice in austral summer 2022

Abstract

The Antarctic sea-ice area reached a record minimum during austral summer 2022 (December 2021 to February 2022), with particularly considerable loss in the West Antarctic. Based on lead–lag correlation analysis, the authors found that the record minimum was closely linked to the preceding near-strongest positive-phase Southern Annular Mode during August–October 2021 and stronger positive SST anomaly in the Maritime Continent during July–September 2021. The former remained at a historically near-strongest or strongest level because of the stratospheric cooling effect of the unprecedented stratospheric ozone depletion, which induced a deepened and southwestward-shifted Amundsen Sea Low (ASL), causing sea-ice retreat via horizontal wind anomalies. The latter persisted into summer and favored the development of La Niña, which generated deep convection over the southwestern subtropical Pacific and triggered a southeastward-propagated Rossby wave train, deepening the ASL remotely. The ozone reduction also induced surface warming in the West Antarctic by increasing the net downward shortwave radiation, thereby intensifying the sea-ice loss. Additionally, positive feedback between the SST, net shortwave radiation and cloudiness, along with the Ekman heat transport, amplified the surface warming.摘要2022年夏季 (2021年12月至2022年2月) 南极海冰面积达到历史新低, 西南极减少最显著. 2021年8∼10月南半球环状模接近历史最强和7∼9月海洋性大陆附近海温显著增暖是两个关键因素. 由于平流层臭氧破纪录减少使得前者维持历史最强或接近最强, 导致阿蒙森低压 (ASL) 加深并向西南移动, 有利于海冰减少. 后者持续到夏季, 有利于拉尼娜的发展, 通过激发罗斯贝波列加深ASL. 在热力上, 臭氧减少导致向下净短波辐射增加, 引起西南极增暖. 此外, 净短波辐射-海温-云形成正反馈, 与埃克曼输送一起, 放大表面增暖, 从而促进海冰融化.