澳大利亚新南威尔士大学Menviel Laurie课题组近日取得一项新成果。他们研究发现，20世纪中期以来由亚北极变冷驱动的大西洋经向翻转环流在减弱。相关论文于2024年11月18日发表在《自然—地球科学》杂志上。

研究人员表示，大西洋经向翻转环流是当今大西洋向北热输送的主要驱动力，它决定了全球气候模式。在过去的一个世纪里，全球变暖是否影响了这种翻转环流的强度仍然存在争议。观测研究表明，自20世纪中叶以来，环流一直在持续减弱，而气候模式系统地模拟了一个稳定的环流。

以地球系统和允许涡旋的耦合海洋-海冰模式为主题，该课题组人员表明，亚北极大西洋的变新鲜和翻转环流的减弱，通过开尔文波和罗斯比波的传播，在十年时间尺度上增加了南大西洋的温度和盐度。

该团队还表明，考虑到历史模拟中高端融水的输入，显著提高了数据模型对大西洋经向翻转环流过去变化的一致性。包括对下个世纪亚北极融水输入的估计表明，在全球变暖2°C的情况下，这种环流可能比其未受人为干扰的状态弱33%，这种翻转环流的减弱将对气候和生态系统产生重大影响。

附：英文原文

Title: Weakening of the Atlantic Meridional Overturning Circulation driven by subarctic freshening since the mid-twentieth century

Author: Pontes, Gabriel M., Menviel, Laurie

Issue&Volume: 2024-11-18

Abstract: The Atlantic Meridional Overturning Circulation is the main driver of northward heat transport in the Atlantic Ocean today, setting global climate patterns. Whether global warming has affected the strength of this overturning circulation over the past century is still debated: observational studies suggest that there has been persistent weakening since the mid-twentieth century, whereas climate models systematically simulate a stable circulation. Here, using Earth system and eddy-permitting coupled ocean–sea-ice models, we show that a freshening of the subarctic Atlantic Ocean and weakening of the overturning circulation increase the temperature and salinity of the South Atlantic on a decadal timescale through the propagation of Kelvin and Rossby waves. We also show that accounting for upper-end meltwater input in historical simulations significantly improves the data–model agreement on past changes in the Atlantic Meridional Overturning Circulation, yielding a slowdown of 0.46sverdrups per decade since 1950. Including estimates of subarctic meltwater input for the coming century suggests that this circulation could be 33% weaker than its anthropogenically unperturbed state under 2°C of global warming, which could be reached over the coming decade. Such a weakening of the overturning circulation would substantially affect the climate and ecosystems.

DOI: 10.1038/s41561-024-01568-1

Source: https://www.nature.com/articles/s41561-024-01568-1