Extracting the Buoyancy-Driven Atlantic Meridional Overturning Circulation
Extracting the Buoyancy-Driven Atlantic Meridional Overturning Circulation
复制标题
提取浮力驱动的大西洋经向翻转环流
DOI：
10.1175/jcli-d-19-0590.1
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发表时间：
2020
影响因子：
4.9
通讯作者：
Clement, Amy C.
中科院分区：
文献类型：
--
作者：
Larson, Sarah M.;Buckley, Martha W.;Clement, Amy C.
由浮力驱动的大西洋纬向翻转环流（AMOC）的变化通常具有低频时间尺度、半球间结构、越赤道热输送以及与北方半球环流和墨西哥湾流强度的联系。本研究首先测试归因于AMOC的这些属性是否在机械解耦的耦合模型中重现，因此仅耦合浮力。总体而言，机械解耦模型再现这些属性，除了在副极地环流，浮力驱动AMOC年际到几十年的时间尺度上的变化，但只有几十年的变化渗透到副热带。一个较强的AMOC与加强北方半球环流，墨西哥湾流，并向北的海洋热输送整个盆地。然后，我们确定是否可以恢复低通滤波的AMOC在一个完全耦合的版本相同的模型，一种常见的方法，用于隔离浮力驱动的AMOC的机械解耦模型中的特性。一个主要的结论是，低通滤波的AMOC在完全耦合的模式再现浮力驱动的AMOC模式和大多数相关的属性，但不是统计的时间变化。AMOC-墨西哥湾流连接的强度也没有重现。分析揭示了在选择指标和滤波技术来估计浮力驱动的AMOC时必须考虑的警告。结果还提供了洞察力的纬度依赖的时间尺度和驱动程序的耦合模式中的海洋环流变化，在真实的世界的浮力驱动的AMOC的测量和检测的潜在影响。
Variations in the Atlantic meridional overturning circulation (AMOC) driven by buoyancy forcing are typically characterized as having a low-frequency time scale, interhemispheric structure, cross-equatorial heat transport, and linkages to the strength of Northern Hemisphere gyre circulations and the Gulf Stream. This study first tests whether these attributes ascribed to the AMOC are reproduced in a coupled model that is mechanically decoupled and, hence, is only buoyancy coupled. Overall, the mechanically decoupled model reproduces these attributes, with the exception that in the subpolar gyre, buoyancy drives AMOC variations on interannual to multidecadal time scales, yet only the multidecadal variations penetrate into the subtropics. A stronger AMOC is associated with a strengthening of the Northern Hemisphere gyre circulations, Gulf Stream, and northward oceanic heat transport throughout the basin. We then determine whether the characteristics in the mechanically decoupled model can be recovered by low-pass filtering the AMOC in a fully coupled version of the same model, a common approach used to isolate the buoyancy-driven AMOC. A major conclusion is that low-pass filtering the AMOC in the fully coupled model reproduces the buoyancy-driven AMOC pattern and most of the associated attributes, but not the statistics of the temporal variability. The strength of the AMOC–Gulf Stream connection is also not reproduced. The analyses reveal caveats that must be considered when choosing indexes and filtering techniques to estimate the buoyancy-driven AMOC. Results also provide insight on the latitudinal dependence of time scales and drivers of ocean circulation variability in coupled models, with potential implications for measurement and detection of the buoyancy-driven AMOC in the real world.
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