2023年南极海冰范围新低事件及其气候意义

A new record low of Antarctic sea ice extent in 2023 and its climatic significance

南极海冰曾长期维持弱增长趋势,但近年来快速减少.紧随2022年新低之后,2023年2月南极海冰范围(SIE)又创下新低纪录178.8万km~2,有观测以来南极SIE首次未经恢复就直接在第二年连续新低,具有重要的气候指示意义.研究显示,SIE初始基数小、大气海洋温度偏高、吸收净太阳辐射异常偏多和来自中纬度的暖平流异常、前春南极涛动和阿蒙森海低压维持异常偏强等是本次海冰新低事件的直接原因,相比于2022年,2023年新低时海冰在东南威德尔海等地进一步减少,而在西北威德尔海等地有所增加,这可能与大气环流在前后两年2月间大气环流的区域变化有关.进一步研究发现,南极海冰和海洋大气温度在过去几十年都经历了趋势变化,其中夏季气温和夏季SIE最小值的趋势转变最早也最显著,近期南极SIE的连续新低和环南极净太阳辐射通量新高等现象可能预示了南极海冰长期趋势转折的确立,后者对于未来南极和全球气候具有关键性影响.

In contrast to the modest growth trend sustained for decades, Antarctic sea ice has declined dramatically in recent years. The Antarctic sea ice extent (SIE) dropped to a new low of 178.8 million square kilometers in February 2023, following the previous record low set in 2022. This makes the first time in observation history that the Antarctic SIE has reached two consecutive record lows. Studies have identified several factors contributing to this new records,including the initially low SIE values, elevated atmospheric and oceanic temperatures, excessive net solar radiation, anomalous warm flows from mid-latitudes, and the persistent intensity of the Antarctic Oscillation (AAO) and Amundsen Sea Low (ASL). Compared to 2022, the sea ice reduction in the areas such as southeast Weddell Sea and the growth in the areas such as northwest Weddell Sea during the 2023 new low, may be linked to regional atmospheric circulation changes between the two successive February. Further investigation indicates a shift in the trend of oceanic and atmospheric temperatures, as well as Antarctic sea ice,over the past decades, with the most significant and earliest shift observed in surface air temperatures and minimum SIE values during the summer. The recent concecutive new lows in Antarctic SIE,along with increased net solar radiation flux around Antarctica, may indicate the a long-term reversal in the Antarctic sea ice trend,potentially impacting future Antarctic and global climates.