The warm sea surface temperature (SST) bias in the Southern Ocean (SO) has persisted in several generations of Coupled Model Inter-comparison Project (CMIP) models, yet the origins of such a bias remain controversial. Using the latest CMIP6 models, here we find that the warm SST bias in the SO features a zonally oriented non-uniform pattern mainly located between the northern and southern fronts of the Antarctic Circumpolar Current. This common bias is not likely to be caused by the biases in the surface heat flux or the strength of the Atlantic meridional overturning circulation (AMOC) — the two previously suggested sources of the SO bias based on CMIP5 models. Instead, it is linked to the robust common warm bias in the Northern Atlantic deep ocean through the AMOC transport as an adiabatic process. Our findings indicate that remote oceanic biases that are dynamically connected to the SO should be taken into account to reduce the SO SST bias in climate models.

南大洋（SO）温暖的海面温度（SST）偏差在几代耦合模式比对项目（CMIP）模型中持续存在，但这种偏差的起源仍然存在争议。使用最新的CMIP6模型，我们发现SO中的暖海温偏差具有纬向方向的不均匀模式，主要位于南极绕极流的北部和南部锋线之间。这种常见的偏差不太可能是由地表热通量的偏差或大西洋经向翻转环流 (AMOC) 的强度引起的——这是之前基于 CMIP5 模型提出的 SO 偏差的两个来源。相反，它通过作为绝热过程的 AMOC 传输与北大西洋深海中强大的共同暖偏差相关。