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The expansion of Antarctic sea ice since 1979 in the presence of increasing greenhouse gases remains one of the most puzzling features of current climate change. Some studies have proposed that the formation of the ozone hole, via the Southern Annular Mode, might explain that expansion, and a recent paper highlighted a robust causal link between summertime Southern Annular Mode (SAM) anomalies and sea ice anomalies in the subsequent autumn. Here we show that many models are able to capture this relationship between the SAM and sea ice, but also emphasize that the SAM only explains a small fraction of the year‐to‐year variability. Finally, examining multidecadal trends, in models and in observations, we confirm the findings of several previous studies and conclude that the SAM–and thus the ozone hole–are not the primary drivers of the sea ice expansion around Antarctica in recent decades.

Eddy heat fluxes play the important role of transferring heat from low to high latitudes, thus affecting midlatitude climate. The recent and projected polar warming, and its effects on the meridional temperature gradients, suggests a possible weakening of eddy heat fluxes. We here examine this question in reanalyses and state-of-the-art global climate models. In the Northern Hemisphere we find that the eddy heat flux has robustly weakened over the last four decades. We further show that this weakening emerged from the internal variability around the year 2000, and we attribute it to increasing greenhouse gases. In contrast, in the Southern Hemisphere we find that the eddy heat flux has robustly strengthened, and we link this strengthening to the recent multi-decadal cooling of Southern-Ocean surface temperatures. The inability of state-of-the-art climate models to simulate such cooling prevents them from capturing the observed Southern Hemisphere strengthening of the eddy heat flux. This discrepancy between models and reanalyses provides a clear example of how model biases in polar regions can affect the midlatitude climate.