Global Impacts of Arctic Sea Ice Loss Mediated by the Atlantic Meridional Overturning Circulation
Global Impacts of Arctic Sea Ice Loss Mediated by the Atlantic Meridional Overturning Circulation
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DOI：
10.1029/2018gl080602
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发表时间：
2019-01-28
影响因子：
5.2
通讯作者：
Fedorov, Alexey V.
中科院分区：
文献类型：
--
作者：
Liu, Wei;Fedorov, Alexey V.
我们在气候模式摄动实验中探索了北极海冰减少对全球的影响，重点是诱导变化的时间演变。我们发现，在较短的十年和较长的几十年到百年的时间尺度之间，气候对实际海冰覆盖减少的反应有很大的不同。在最初的20年里，当大气过程占主导地位时，海冰的减少导致了表面温度的“两极拉锯”模式，北半球变暖，南半球变冷，导致热带辐合带向北移动，南极海冰扩张。相比之下，在几十年和更长的时间尺度上，从北极扩散的上层海洋浮力异常导致的大西洋经向翻转环流减弱，调解了海冰的直接影响，几乎逆转了北极以外的原始响应模式。南半球变暖，北大西洋出现增温洞，热带辐合区向南移动，南极海冰收缩。为了了解最近北冰洋海冰的减少可能会如何影响全球气候，我们进行了模型实验，其中我们修改了北冰洋海冰的性质，以模拟与观测结果相似的北极海冰消失。我们发现，在海冰消退后的不同时期，气候响应呈现出明显不同的模式。在最初的一二十年里，北极海冰的减少允许更多的太阳能进入北半球，改变了地球的能量平衡。随着北半球变暖而南半球变冷，热带雨带向北移动，南极海冰扩大。然而，再过几十年到一个世纪后，深海变化的影响变得更加重要，最终压倒了海冰消失对大气的直接影响。大西洋深海环流的减弱导致北大西洋变冷，南半球变暖。南极海冰收缩，热带雨带回到原来的位置，并进一步向南移动。
We explore the global impacts of Arctic sea ice decline in climate model perturbation experiments focusing on the temporal evolution of induced changes. We find that climate response to a realistic reduction in sea ice cover varies dramatically between shorter decadal and longer multidecadal to centennial timescales. During the first two decades, when atmospheric processes dominate, sea ice decline induces a "bipolar seesaw" pattern in surface temperature with warming in the Northern and cooling in the Southern Hemisphere, leading to a northward displacement of the Intertropical Convergence Zone and an expansion of Antarctic sea ice. In contrast, on multidecadal and longer timescales, the weakening of the Atlantic meridional overturning circulation, caused by upper-ocean buoyancy anomalies spreading from the Arctic, mediates direct sea ice impacts and nearly reverses the original response pattern outside the Arctic. The Southern Hemisphere warms, a Warming Hole emerges in the North Atlantic, the Intertropical Convergence Zone shifts southward, and Antarctic sea ice contracts.Plain Language Summary To understand how the recent Arctic sea ice decline may affect global climate, we conduct model experiments in which we modify the properties of Arctic sea ice, in order to simulate an Arctic sea ice loss similar to the observed. We find that climate response shows dramatically different patterns during different periods after the imposed sea ice decline. During the first one or two decades, Arctic sea ice decline allows more solar energy into the Northern Hemisphere, altering the Earth's energy balance. As the Northern Hemisphere warms while the Southern Hemisphere cools, the tropical rain belt moves northward, and Antarctic sea ice expands. However, after several more decades to a century, the impacts from changes in the deep ocean become more important and eventually overwhelm the direct effects of sea ice loss on the atmosphere. The weakening of the Atlantic deep ocean circulation causes a cooling in the North Atlantic and a warming in the Southern Hemisphere. Antarctic sea ice contracts and the tropical rain belt shifts back to its original position and further south.