Labrador Sea subsurface density as a precursor of multidecadal variability in the North Atlantic: a multi-model study
Labrador Sea subsurface density as a precursor of multidecadal variability in the North Atlantic: a multi-model study
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DOI：
10.5194/esd-12-419-2021
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发表时间：
2021-04-26
影响因子：
7.3
通讯作者：
Yeager, Stephen
中科院分区：
文献类型：
--
作者：
Ortega, Pablo;Robson, Jon, I;Yeager, Stephen
亚极地北大西洋(SPNA)是一个具有显著年代际变化的区域，在过去几十年中经历了显着的变暖和变冷趋势。在观察到这些趋势之前，拉布拉多海密度(LSD)出现了缓慢的上升和下降，这被认为是大规模海洋环流变化的前兆。本文通过一组耦合的气候模式模拟，分析了LSD和更广阔的北大西洋之间的相互关系。特别是分析了次表层密度与深边界密度、大西洋子午线翻转环流(AMOC)、亚极涡旋(SPG)环流和SPNA东部上层海洋温度之间的关系。所有模拟结果都显示出LSD和海洋环流指数具有相当大的年代际变化，这些变化被发现是相关的。LSD与亚极AMOC和涡旋环流的强度有很强的联系，也与副热带AMOC有关，尽管这种关系的强度与模式有关，并受到Ekman分量的影响。LSD与副热带的连通性对不同的模式特征很敏感，包括拉布拉多海的平均密度层结、AMOC的强度和深度以及LSD沿西部边界向南传播的深度。这些量中的几个也可以从观测中计算出来，与这些基于观测的量进行比较表明，代表与副热带AMOC较弱联系的模型可能更现实。
The subpolar North Atlantic (SPNA) is a region with prominent decadal variability that has experienced remarkable warming and cooling trends in the last few decades. These observed trends have been preceded by slow-paced increases and decreases in the Labrador Sea density (LSD), which are thought to be a precursor of large-scale ocean circulation changes. This article analyses the interrelationships between the LSD and the wider North Atlantic across an ensemble of coupled climate model simulations. In particular, it analyses the link between subsurface density and the deep boundary density, the Atlantic Meridional Overturning Circulation (AMOC), the subpolar gyre (SPG) circulation, and the upper-ocean temperature in the eastern SPNA.All simulations exhibit considerable multidecadal variability in the LSD and the ocean circulation indices, which are found to be interrelated. LSD is strongly linked to the strength of the subpolar AMOC and gyre circulation, and it is also linked to the subtropical AMOC, although the strength of this relationship is model-dependent and affected by the inclusion of the Ekman component. The connectivity of LSD with the subtropics is found to be sensitive to different model features, including the mean density stratification in the Labrador Sea, the strength and depth of the AMOC, and the depth at which the LSD propagates southward along the western boundary. Several of these quantities can also be computed from observations, and comparison with these observation-based quantities suggests that models representing a weaker link to the subtropical AMOC might be more realistic.