Atmospheric influences on the anomalous 2016 Antarctic sea ice decay
Atmospheric influences on the anomalous 2016 Antarctic sea ice decay
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DOI：
10.5194/tc-12-1103-2018
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发表时间：
2017-09
期刊：
影响因子：
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通讯作者：
E. Schlosser;F. Haumann;M. Raphael
中科院分区：
文献类型：
--
作者：
E. Schlosser;F. Haumann;M. Raphael
抽象的。在过去的三十年里，北极的海冰总面积一直在减少，与此相反，南极的海冰总面积在同一时期出现了小幅但显著的增加。然而，在2016年，观察到融化季节的异常提前;最大南极SIE早在8月就已经达到，而不是9月底，随后迅速下降。衰减在11月特别强烈，当时南极SIE显示出约200万平方公里的负异常（与1979-2015年的平均值相比）。ECMWF中期再分析数据表明，融化的早期开始以及海冰面积（SIA）和SIE的快速减少与与正的纬向波数3（ZW 3）指数相关的大气流型有关，即，在海冰减少最强的地区，天气形势导致强纬向流和异常强烈的向南热平流。从5月到8月，ZW 3指数持续为正，表明SIE下降是SIA下降的先决条件。特别是在11月的前三分之一，威德尔海和西太平洋的偏北气流条件引发了海冰加速衰减，由于正反馈效应，海冰在接下来的几周内继续衰减，导致11月SIE异常低。2016年，月平均南方环形模式（SAM）指数达到自卫星观测开始以来的第二低11月值。为了评估冰量而不是冰面积的变化，需要在空间和时间上更好地提供可靠的冰厚数据。
Abstract. In contrast to the Arctic, where total sea ice extent (SIE) has been decreasing for the last three decades, Antarctic SIE has shown a small, but significant, increase during the same time period. However, in 2016, an unusually early onset of the melt season was observed; the maximum Antarctic SIE was already reached as early as August rather than the end of September, and was followed by a rapid decrease. The decay was particularly strong in November, when Antarctic SIE exhibited a negative anomaly (compared to the 1979–2015 average) of approximately 2 million km2. ECMWF Interim reanalysis data showed that the early onset of the melt and the rapid decrease in sea ice area (SIA) and SIE were associated with atmospheric flow patterns related to a positive zonal wave number three (ZW3) index, i.e., synoptic situations leading to strong meridional flow and anomalously strong southward heat advection in the regions of strongest sea ice decline. A persistently positive ZW3 index from May to August suggests that SIE decrease was preconditioned by SIA decrease. In particular, in the first third of November northerly flow conditions in the Weddell Sea and the Western Pacific triggered accelerated sea ice decay, which was continued in the following weeks due to positive feedback effects, leading to the unusually low November SIE. In 2016, the monthly mean Southern Annular Mode (SAM) index reached its second lowest November value since the beginning of the satellite observations. A better spatial and temporal coverage of reliable ice thickness data is needed to assess the change in ice mass rather than ice area.