Persistent freshening of the Arctic Ocean and changes in the North Atlantic salinity caused by Arctic sea ice decline
Persistent freshening of the Arctic Ocean and changes in the North Atlantic salinity caused by Arctic sea ice decline
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北极海冰减少导致北冰洋持续清新和北大西洋盐度变化
DOI：
10.1007/s00382-021-05850-5
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发表时间：
2021
期刊：
影响因子：
4.6
通讯作者：
Fedorov, Alexey V.
中科院分区：
文献类型：
--
作者：
Li, Hui;Fedorov, Alexey V.
北冰洋海冰在过去几十年里一直在减少，最大的冰消融发生在夏季。这意味着海冰季节性循环的加强。在这里，我们使用模拟来研究全球海洋盐度对北极海冰这种变化的响应，在模拟中，我们在海冰表面施加辐射热不平衡，导致海冰下降，与观测结果相当。施加的扰动导致季节性融化加剧，北极海冰在最初的5-10年内迅速消退。然后，我们观察到北冰洋上部的海水逐渐变淡，这一过程持续了大约一个世纪。这种淡化在包括波弗特环流在内的北极中部地区最为明显，原因是季节性海冰融化加剧导致地表淡水过剩，以及海洋环流变化导致上层海洋淡水储存增加。北欧海的淡化也可以通过类似蒸馏的过程发生，在这种过程中，盐度增加的更稠密的咸水通过经向翻转环流输出到亚热带/热带北大西洋。因此，在气候变暖的情况下，季节性海冰融化的加剧可能会导致北极的持续清新，对全球盐度分布产生重大影响。
Arctic sea ice has been declining over past several decades with the largest ice loss occurring in summer. This implies a strengthening of the sea ice seasonal cycle. Here, we examine global ocean salinity response to such changes of Arctic sea ice using simulations wherein we impose a radiative heat imbalance at the sea ice surface, inducing a sea ice decline comparable to the observed. The imposed perturbation leads to enhanced seasonal melting and a rapid retreat of Arctic sea ice within the first 5–10 years. We then observe a gradual freshening of the upper Arctic ocean that continues for about a century. The freshening is most pronounced within the central Arctic, including the Beaufort gyre, and is attributed to excess surface freshwater associated with the stronger seasonal sea ice melting, as well as a greater upper-ocean freshwater storage due to changes in ocean circulation. The freshening of the Nordic Seas can also occur via a distillation-like process in which denser saline waters with increased salinity are exported to the subtropical/tropical North Atlantic by meridional overturning circulation. Thus, enhanced seasonal sea ice melting in a warmer climate can lead to a persistent Arctic freshening with large impacts on the global salinity distribution.
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