Roles of wind stress and thermodynamic forcing in recent trends in Antarctic sea ice and Southern Ocean SST: an ocean-sea ice model study
Roles of wind stress and thermodynamic forcing in recent trends in Antarctic sea ice and Southern Ocean SST: an ocean-sea ice model study
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DOI：
10.1016/j.gloplacha.2017.09.012
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发表时间：
2017-11
影响因子：
3.9
通讯作者：
K. Kusahara;G. Williams;R. Massom;P. Reid;H. Hasumi
中科院分区：
文献类型：
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作者：
K. Kusahara;G. Williams;R. Massom;P. Reid;H. Hasumi
与北极海冰范围的大幅减少相反，自 1979 年以来，南极海冰总体范围略有增加。人们对南极海冰净扩张提出了几种假设，包括大气/海洋环流和温度变化、海冰-大气-海洋反馈、降水增加以及冰架基础融水增加。与南极海冰的这一积极趋势相伴，南纬约 45°以南的南大洋海面温度 (SST) 在此期间有所降温。然而，南极海冰扩张和海温变冷趋势的机制仍不清楚。在这里，我们使用具有稳态冰架成分的海洋-海冰耦合模型进行了全面的敏感性实验，以研究南极海冰和南大洋海表温度近期趋势的主要驱动因素。结果表明，南极海冰的扩张主要是由热力学表面强迫的趋势来解释的，特别是冷却和干燥以及长波辐射的减少。同样，热力学强迫被发现是纬向海温冷却趋势的主要驱动力。虽然风应力对海冰范围和海温的影响显然较小，但它在海冰运动、沿海海冰增厚以及阿蒙森-罗斯东部海和冬春 65-95°E 中部地区的冰变薄和浓度方面起着关键作用。此外，该模型表明，海冰架相互作用不会显着影响近几十年来观测到的南极海冰覆盖和南大洋海表温度的趋势。
In contrast to a strong decrease in Arctic sea ice extent, overall Antarctic sea ice extent has modestly increased since 1979. Several hypotheses have been proposed for the net Antarctic sea ice expansion, including atmosphere/ocean circulation and temperature changes, sea ice-atmospheric-ocean feedback, increased precipitation, and enhanced basal meltwater from ice shelves. Concomitant with this positive trend in Antarctic sea ice, sea surface temperatures (SSTs) over the Southern Ocean south of approximately 45°S have cooled over this period. However, the mechanisms responsible for the Antarctic sea ice expansion and the SST cooling trend remain poorly defined. Here, we conduct comprehensive sensitivity experiments using a coupled ocean-sea ice model with a steady-state ice shelf component in order to investigate the main drivers of recent trends in Antarctic sea ice and SST over the Southern Ocean. The results suggest that Antarctic sea ice expansion is mostly explained by trends in the thermodynamic surface forcing, notably cooling and drying and a reduction in longwave radiation. Similarly, thermodynamic forcing is found to be the main driver of the zonal SST cooling trend. While apparently less influential on sea ice extent and SST, wind stress plays a key role in sea ice motion, thickening coastal sea ice, and thinning and decreasing the concentration of ice in mid-pack regions of the Amundsen-eastern Ross seas and 65–95°E in winter-spring. Furthermore, the model suggests that ocean-ice shelf interaction does not significantly influence the observed trends in Antarctic sea ice coverage and Southern Ocean SST in recent decades.