Teleconnection between the Atlantic Meridional Overturning Circulation and Sea Level in the Mediterranean Sea
Teleconnection between the Atlantic Meridional Overturning Circulation and Sea Level in the Mediterranean Sea
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DOI：
10.1175/jcli-d-18-0474.1
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发表时间：
2019-01
影响因子：
4.9
通讯作者：
D. Volkov;M. Baringer;D. Smeed;W. Johns;F. Landerer
中科院分区：
文献类型：
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作者：
D. Volkov;M. Baringer;D. Smeed;W. Johns;F. Landerer
地中海可以被看作是北大西洋的“晴雨表”，因为它的海平面对与北大西洋涛动（NAO）有关的大气压力和风强迫的海洋环流尺度变化作出反应。北大西洋的气候受到大西洋经向翻转环流（AMOC）的影响，因为它将热量从南大西洋输送到近极地的北大西洋。本研究报告了2004 - 2017年在26.5°N测量的AMOC输送与地中海海平面之间的遥相关关系：AMOC输送的减少/增加与地中海海平面的升高/降低有关。利用现有的卫星和现场观测以及大气再分析，详细分析了造成这种遥相关的过程。首先，在月至年际时间尺度上，AMOC和海平面都是由类似nao的大气环流模式驱动的。在正/负NAO状态期间，更强/更弱的信风(i)驱动横跨26.5°N的Ekman运输向北/南向异常，直接影响AMOC； （ii）与直布罗陀海峡上空的西/东风有关，迫使水流出/流入地中海，从而改变其平均海平面。其次，AMOC输运的年际变化可导致北大西洋东部边界附近的热阻性海平面异常。这些异常可以(i)到达直布罗陀海峡并引起地中海的海平面变化，（ii）代表AMOC负反馈的机制。
The Mediterranean Sea can be viewed as a “barometer” of the North Atlantic Ocean, because its sea level responds to oceanic-gyre-scale changes in atmospheric pressure and wind forcing, related to the North Atlantic Oscillation (NAO). The climate of the North Atlantic is influenced by the Atlantic meridional overturning circulation (AMOC) as it transports heat from the South Atlantic toward the subpolar North Atlantic. This study reports on a teleconnection between the AMOC transport measured at 26.5°N and the Mediterranean Sea level during 2004–17: a reduced/increased AMOC transport is associated with a higher/lower sea level in the Mediterranean. Processes responsible for this teleconnection are analyzed in detail using available satellite and in situ observations and an atmospheric reanalysis. First, it is shown that on monthly to interannual time scales the AMOC and sea level are both driven by similar NAO-like atmospheric circulation patterns. During a positive/negative NAO state, stronger/weaker trade winds (i) drive northward/southward anomalies of Ekman transport across 26.5°N that directly affect the AMOC and (ii) are associated with westward/eastward winds over the Strait of Gibraltar that force water to flow out of/into the Mediterranean Sea and thus change its average sea level. Second, it is demonstrated that interannual changes in the AMOC transport can lead to thermosteric sea level anomalies near the North Atlantic eastern boundary. These anomalies can (i) reach the Strait of Gibraltar and cause sea level changes in the Mediterranean Sea and (ii) represent a mechanism for negative feedback on the AMOC.