Potsdam Institute for Climate Impact Research (PIK), Potsdam, Germany.
Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany.
Nature. 2018 Apr;556(7700):191-196. doi: 10.1038/s41586-018-0006-5. Epub 2018 Apr 11.
The Atlantic meridional overturning circulation (AMOC)-a system of ocean currents in the North Atlantic-has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature 'fingerprint'-consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region-and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years.
北大西洋经向翻转环流（AMOC）——北大西洋的一种海流系统——对气候有重大影响，但由于缺乏直接的海流测量，其在工业时代的演变情况知之甚少。本文提供的证据表明，自 20 世纪中叶以来，AMOC 减弱了约 3±1 立方每秒（约 15%）。这种减弱是通过亚极地北大西洋的冷却和墨西哥湾流区域的变暖的特征空间和季节性海面温度“指纹”来揭示的，该指纹是通过 CMIP5 项目中的模型模拟集合来校准的。我们在一个对大气二氧化碳浓度增加做出响应的高分辨率气候模型中以及在自 19 世纪末以来观测到的温度趋势中都发现了这种指纹。这种模式可以用 AMOC 的减缓以及向北的热量输送减少来解释，同时还有墨西哥湾流的北移。与 RAPID 项目和其他几项研究的最近直接测量结果进行比较，提供了近年来 AMOC 值创纪录低的一致描述。
