Indian Ocean warming can strengthen the Atlantic meridional overturning circulation
Indian Ocean warming can strengthen the Atlantic meridional overturning circulation
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DOI：
10.1038/s41558-019-0566-x
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发表时间：
2019-10-01
影响因子：
30.7
通讯作者：
Fedorov, Alexey, V
中科院分区：
文献类型：
--
作者：
Hu, Shineng;Fedorov, Alexey, V
大西洋纬向翻转环流（AMOC）的减缓（1-3）和热带印度洋（TIO）的加速变暖（4-6）是人为温室效应的两个强大特征，影响区域和全球气候（7，8）。在这里，我们使用耦合的气候模拟来研究这两种现象之间以前被忽视的联系。我们证明，TIO变暖减少了热带大西洋的降雨，通过加强步行者环流和增加大气垂直稳定度。由于盐度异常被平流输送到北方高纬度地区，由此产生的海洋盐度增加加剧了AMOC。此外，TIO变暖增强了副极地北大西洋的西风，这有助于维持更强的AMOC。热带海洋平均变暖0.1摄氏度以上的TIO变暖加剧了AMOC类似1 Sv，导致更强的半球间不对称性和向北移动的ITCZ。因此，TIO变暖可以延缓温室效应下AMOC的减弱。事实上，我们发现，AMOC削弱更强烈或完全崩溃，如果我们抑制TIO变暖的两倍和四倍的CO2情景。模拟复制观测到的热带海洋变暖进一步证实了TIO-AMOC的联系，这表明观测到的TIO变暖可能已经在维持AMOC方面发挥了作用。
The slowdown of the Atlantic meridional overturning circulation (AMOC)(1-3) and the accelerated warming of the tropical Indian Ocean (TIO)(4-6) are two robust features projected for anthropogenic greenhouse warming, affecting both regional and global climates(7,8). Here we use coupled climate simulations to investigate a previously overlooked link between the two phenomena. We demonstrate that TIO warming reduces rainfall over the tropical Atlantic by strengthening the Walker circulation and increasing atmospheric vertical stability. The resultant ocean salinity increase intensifies the AMOC as salinity anomalies are advected to northern high latitudes. In addition, TIO warming enhances westerly winds over the subpolar North Atlantic, which helps to maintain the stronger AMOC. A TIO warming of 0.1 degrees C above the mean warming of tropical oceans intensifies the AMOC by similar to 1 Sv, leading to a stronger interhemispheric asymmetry and a northward shifted ITCZ. Thus, TIO warming could delay the AMOC weakening under greenhouse warming. Indeed, we find that the AMOC weakens more strongly or completely collapses if we suppress TIO warming under the doubled and quadrupled CO2 scenarios. Simulations replicating the observed tropical ocean warming further confirm this TIO-AMOC link, suggesting that the observed TIO warming might be already playing a role in sustaining the AMOC.