Seawater density variations in the North Atlantic and the Atlantic meridional overturning circulation
Seawater density variations in the North Atlantic and the Atlantic meridional overturning circulation
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DOI：
10.1007/s00382-009-0560-5
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发表时间：
2010-06
期刊：
影响因子：
4.6
通讯作者：
Chunzai Wang;S. Dong;E. Muñoz
中科院分区：
文献类型：
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作者：
Chunzai Wang;S. Dong;E. Muñoz
北大西洋海水性质的变化影响着大西洋纬向翻转环流（AMOC），它将上层海洋的暖水向北输送，对欧洲的温带气候有贡献，并影响着全球气候。以前的观测研究集中在北大西洋下沉区域的盐度和淡水变化，因为人们认为，北大西洋盆地的清新可以减缓或停止AMOC的流动。在这里，我们使用现有的数据来显示北大西洋上层海洋的密度模式如何影响AMOC的强度的重要性。就长期趋势而言，副极地北大西洋的上层海洋正变得更冷、更新鲜，而副热带北大西洋正变得更暖、更咸。在几十年的时间尺度上，自1995年以来，北大西洋上层海洋总体上更加温暖和咸。副极地北大西洋的热盐含量滞后于副热带北大西洋约8-9年，表明温度和盐度异常的低纬度起源。由于温度和盐度对密度的长期趋势和几十年的时间尺度的相反的影响，这些变化不会导致密度降低在副极地北大西洋减缓AMOC。事实上，副极地和亚热带北大西洋之间纬向密度梯度的变化表明，AMOC在过去的50年里变得更强了。这些观测结果得到了一些海洋再分析产品的支持和一致。
Seawater property changes in the North Atlantic Ocean affect the Atlantic meridional overturning circulation (AMOC), which transports warm water northward from the upper ocean and contributes to the temperate climate of Europe, as well as influences climate globally. Previous observational studies have focused on salinity and freshwater variability in the sinking region of the North Atlantic, since it is believed that a freshening North Atlantic basin can slow down or halt the flow of the AMOC. Here we use available data to show the importance of how density patterns over the upper ocean of the North Atlantic affect the strength of the AMOC. For the long-term trend, the upper ocean of the subpolar North Atlantic is becoming cooler and fresher, whereas the subtropical North Atlantic is becoming warmer and saltier. On a multidecadal timescale, the upper ocean of the North Atlantic has generally been warmer and saltier since 1995. The heat and salt content in the subpolar North Atlantic lags that in the subtropical North Atlantic by about 8–9 years, suggesting a lower latitude origin for the temperature and salinity anomalies. Because of the opposite effects of temperature and salinity on density for both long-term trend and multidecadal timescales, these variations do not result in a density reduction in the subpolar North Atlantic for slowing down the AMOC. Indeed, the variations in the meridional density gradient between the subpolar and subtropical North Atlantic Ocean suggest that the AMOC has become stronger over the past five decades. These observed results are supported by and consistent with some oceanic reanalysis products.