Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean
Weakening of Cold Halocline Layer Exposes Sea Ice to Oceanic Heat in the Eastern Arctic Ocean
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DOI：
10.1175/jcli-d-19-0976.1
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发表时间：
2020-09-15
影响因子：
4.9
通讯作者：
Rember, Robert
中科院分区：
文献类型：
--
作者：
Polyakova, Igor, V;Rippeth, Tom P.;Rember, Robert
本文利用北冰洋欧亚海盆东部（>70 ° E）15年来的系泊观测记录，研究了近年来中深（150- 900 m）暖大西洋水（AW）到表层混合层和海冰的海洋热通量的增加。大气热量的向上释放受上覆盐跃层的稳定性的控制，我们发现盐跃层的稳定性近年来已经大大减弱。浅水化也有贡献，2017-18年冬季的观测显示，AWat只有80米深，就在冬季表面混合层之下，这是我们系泊记录中最浅的。盐跃层在这个时候减弱了几个月，这意味着AW热量与海冰形成过程中与盐水排斥有关的冬季对流有关。这导致了冬季海洋热通量的大幅增加，从2007-08年的平均3- 4 Wm（-2）增加到2016-18年的10 Wm（-2）。东部夏季的热量损失相当于冬季冰增长减少了两倍多。这些变化意味着一个积极的反馈，减少海冰覆盖允许增加混合，增强夏季主导的冰-冰反馈。
A 15-yr duration record of mooring observations from the eastern (>70 degrees E) Eurasian Basin (EB) of the Arctic Ocean is used to show and quantify the recently increased oceanic heat flux from intermediate-depth (similar to 150-900m) warmAtlantic Water (AW) to the surfacemixed layer and sea ice. The upward release ofAWheat is regulated by the stability of the overlying halocline, which we show has weakened substantially in recent years. Shoaling of theAWhas also contributed, with observations in winter 2017-18 showing AWat only 80m depth, just below the wintertime surfacemixed layer, the shallowest in our mooring records. The weakening of the halocline for several months at this time implies that AW heat was linked to winter convection associated with brine rejection during sea ice formation. This resulted in a substantial increase of upward oceanic heat flux during the winter season, froman average of 3-4W m(-2) in 2007-08 to.10Wm(-2) in 2016-18. This seasonalAWheat loss in the easternEBis equivalent to a more than a twofold reduction of winter ice growth. These changes imply a positive feedback as reduced sea ice cover permits increased mixing, augmenting the summer-dominated ice-albedo feedback.