Agulhas leakage dynamics affects decadal variability in Atlantic overturning circulation
Agulhas leakage dynamics affects decadal variability in Atlantic overturning circulation
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DOI：
10.1038/nature07426
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发表时间：
2008-11-27
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.
预测十年尺度上的气候演变需要对控制纬向翻转环流（MOC）的动力学有定量的了解（1）。在北大西洋亚热带地区建立了旨在监测MOC变化的综合海洋测量方案（2、3）（RAPID，北纬26.56度，MOVE，北纬16度），这些方案显示出季节内到年际时间尺度上的强烈变化。由于在过去几十年中很少对跨洋剖面进行采样，因此MOC输送的长期变化的观测证据仍然很少（4、5）。然而，基于长期海表温度记录的推断，得到了模式模拟的支持，表明在亚热带地区，十年时间尺度上的变化幅度为+/- 1.5-3 Sv（1 Sv = 10（6）m（3）s（-1））（6）。这种变化归因于亚北极大西洋深水形成的变化，特别是拉布拉多海水的更新率（7）。在这里，我们提出了一个模型模拟的结果，表明一个额外的影响十年MOC变化有一个南半球的起源：动态信号起源于非洲南端的Agulhas泄漏区域。这些在热带和亚热带北大西洋中贡献了与北方源相同量级的MOC信号。因此，要使观测到的主运行中心变化完全合理化，还需要考虑来自南方的信号。
Predicting the evolution of climate over decadal timescales requires a quantitative understanding of the dynamics that govern the meridional overturning circulation (MOC)(1). Comprehensive ocean measurement programmes aiming to monitor MOC variations have been established in the subtropical North Atlantic(2,3) ( RAPID, at latitude 26.56 degrees N, and MOVE, at latitude 16 degrees N) and show strong variability on intraseasonal to interannual timescales. Observational evidence of longer- term changes in MOC transport remains scarce, owing to infrequent sampling of transoceanic sections over past decades(4,5). Inferences based on long- term sea surface temperature records, however, supported by model simulations, suggest a variability with an amplitude of +/- 1.5-3 Sv ( 1 Sv = 10(6) m(3) s(-1)) on decadal timescales in the subtropics(6). Such variability has been attributed to variations of deep water formation in the sub- arctic Atlantic, particularly the renewal rate of Labrador Sea Water(7). Here we present results from a model simulation that suggest an additional influence on decadal MOC variability having a Southern Hemisphere origin: dynamic signals originating in the Agulhas leakage region at the southern tip of Africa. These contribute a MOC signal in the tropical and subtropical North Atlantic that is of the same order of magnitude as the northern source. A complete rationalization of observed MOC changes therefore also requires consideration of signals arriving from the south.