Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies
Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies
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DOI：
10.1038/nature08519
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发表时间：
2009-11-26
期刊：
影响因子：
64.8
通讯作者：
Lutjeharms, J. R. E.
中科院分区：
文献类型：
--
作者：
Biastoch, A.;Boening, C. W.;Lutjeharms, J. R. E.
印度洋温暖和咸的沃茨进入大西洋的过程--厄古拉斯泄漏--在全球海洋环流中起着至关重要的作用（1），因此也是未来气候演变的关键。目前，这些沃茨为大西洋纬向翻转环流（MOC）的表面分支提供了主要的热量和盐分来源（2）。有孔虫组合（3）和模型研究（4）中过去冰期到间冰期的变化有证据表明，Agulhas泄漏量及其对MOC的相应影响发生了重大变化，可能与南半球西风带的纬度变化有关（5）。在过去的二、三十年中，观测到西风带逐渐向极地迁移，这与人为强迫有关（6），但由于观测记录稀少，因此无法确定是否伴随着阿古拉斯泄漏的响应。在这里，我们提出了一个高分辨率的海洋环流模式（7，8）的结果表明，在过去的几十年中，印度洋沃茨的运输到南大西洋通过Agulhas泄漏增加，响应风强迫的变化。渗漏的增加导致了南大西洋温跃层沃茨的盐化（9）。南美洲近海的模型和历史测量都表明，额外的印度洋沃茨已经开始侵入北大西洋，这对MOC的未来演变具有潜在的影响。
The transport of warm and salty Indian Ocean waters into the Atlantic Ocean-the Agulhas leakage-has a crucial role in the global oceanic circulation(1) and thus the evolution of future climate. At present these waters provide the main source of heat and salt for the surface branch of the Atlantic meridional overturning circulation (MOC)(2). There is evidence from past glacial-to-interglacial variations in foraminiferal assemblages(3) and model studies(4) that the amount of Agulhas leakage and its corresponding effect on the MOC has been subject to substantial change, potentially linked to latitudinal shifts in the Southern Hemisphere westerlies(5). A progressive poleward migration of the westerlies has been observed during the past two to three decades and linked to anthropogenic forcing(6), but because of the sparse observational records it has not been possible to determine whether there has been a concomitant response of Agulhas leakage. Here we present the results of a high-resolution ocean general circulation model(7,8) to show that the transport of Indian Ocean waters into the South Atlantic via the Agulhas leakage has increased during the past decades in response to the change in wind forcing. The increased leakage has contributed to the observed salinification(9) of South Atlantic thermocline waters. Both model and historic measurements off South America suggest that the additional Indian Ocean waters have begun to invade the North Atlantic, with potential implications for the future evolution of the MOC.