Kramer Sydney M, Karnauskas Kristopher B, Zhang Lei, Heede Ulla K, Liu Heng
Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, USA.
Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, USA.
Sci Rep. 2024 Nov 30;14(1):29829. doi: 10.1038/s41598-024-80381-7.
A persistent cooling trend in the subpolar North Atlantic known as the North Atlantic Warming Hole (NAWH) has appeared in sea surface temperature (SST) observations since 1870, and the reasons for its persistence in an era of rapid anthropogenic global warming remain elusive. Here we investigate the response of the atmosphere to the NAWH in a set of model experiments, and further examine the associated feedback mechanisms. In one experiment, the observed warming hole is imposed upon the present-day climatology, and in another we run a sensitivity experiment, shifting the location of the warming hole southward of its observed location to limit its direct interaction with the jet stream. Surprisingly, the response of the jet stream and surface circulation is relatively insensitive to the latitude of the NAWH within the basin. However, the capacity for the atmospheric response to invoke a positive feedback onto the SST forcing does depend on proximity to the midlatitude jet stream. These results distinctly differ from similar coarser resolution experiments but align with observed patterns, highlighting the importance of eddies in determining the response of the midlatitude atmosphere to persistent SST forcing. These findings therefore augment our understanding of the long-term persistence of the NAWH.
自1870年以来，在海表温度（SST）观测中出现了一种持续的亚极地北大西洋变冷趋势，即北大西洋暖池（NAWH），而在人为导致全球快速变暖的时代，其持续存在的原因仍然不明。在此，我们在一组模型实验中研究了大气对NAWH的响应，并进一步考察了相关的反馈机制。在一个实验中，将观测到的暖池施加到当前气候上，在另一个实验中，我们进行了一个敏感性实验，将暖池的位置向其观测位置以南移动，以限制其与急流的直接相互作用。令人惊讶的是，盆地内急流和表面环流的响应对NAWH的纬度相对不敏感。然而，大气响应在SST强迫上引发正反馈的能力确实取决于与中纬度急流的接近程度。这些结果明显不同于类似的低分辨率实验，但与观测模式相符，突出了涡旋在确定中纬度大气对持续SST强迫响应方面的重要性。因此，这些发现增进了我们对NAWH长期持续存在的理解。
