Opposing decadal changes for the North Atlantic meridional overturning circulation
Opposing decadal changes for the North Atlantic meridional overturning circulation
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DOI：
10.1038/ngeo947
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发表时间：
2010-10-01
影响因子：
18.3
通讯作者：
Williams, Richard G.
中科院分区：
文献类型：
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作者：
Lozier, M. Susan;Roussenov, Vassil;Williams, Richard G.
1950年至2000年，北大西洋的水文特性发生了显著变化：亚热带变暖，变得更加咸，而副极地海洋冷却和清新。这些变化直接影响海洋中热量和淡水的储存，但它们对海洋动力学的影响取决于海水密度的变化。在这里，我们使用历史水文数据表明，在北大西洋盆地的整体海水密度下降，在这50年期间。由于这些密度的变化，海面高度的变化在空间上变化的模式与2毫米年（-1）的典型率，在广泛的协议与验潮仪测量。将观测到的密度场与数值模式相结合，我们发现副热带环流的翻转略微减弱了-1.5 +/-1Sv，而副极地环流的翻转略微加强了-0.8 +/-0.5Sv。这些特定于涡旋的变化与单一流域尺度翻转环流的经典概念背道而驰，可能反映了年际和十年的趋势，而不是任何长期气候趋势。我们的结论是，环流动力学强烈影响温度和盐度的变化，转化为纬向翻转环流的变化。
The hydrographic properties of the North Atlantic Ocean changed significantly from 1950 to 2000: the subtropics warmed and became more saline, whereas the subpolar ocean cooled and freshened. These changes directly affect the storage of heat and fresh water in the ocean, but their consequences for ocean dynamics are determined by the resultant changes in seawater density. Here we use historical hydrographic data to show that the overall seawater density in the North Atlantic basin decreased during this 50-year period. As a result of these density changes, sea-surface heights changed in a spatially varying pattern with typical rates of 2 mm yr(-1), in broad agreement with tide-gauge measurements. Melding the observed density fields within a numerical model we find a slight weakening in the overturning of the subtropical gyre by -1.5 +/- 1Sv and a slight strengthening in the overturning of the subpolar gyre by -0.8 +/- 0.5Sv. These gyre-specific changes run counter to the canonical notion of a single, basin-scale overturning cell and probably reflect interannual and decadal trends rather than any long-term climate trend. We conclude that gyre dynamics strongly affect temperature and salinity changes that translate into changes in the meridional overturning circulation.