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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. Plain Language Summary: Unlike its Arctic counterpart, sea ice around Antarctica has been growing since 1979, even as the levels of carbon dioxide in the atmosphere have increased. Given that the ozone hole formed over the South Pole around the same time, one is led to ask whether the ozone hole may be responsible for the growth of Antarctic sea ice (recall that there is no ozone hole over the North Pole). In this study, looking at both models and observations, we show that the ozone hole is capable of affecting the surface winds and these, in turn, can make sea ice expand. However, the magnitude of this effect is small. Also since the ozone hole started healing after the year 2000, while Antarctic sea ice kept expanding, we conclude that ozone depletion is not the main reason for the expansion of Antarctic sea ice in recent decades. Key Points: Many CMIP5 models are able to capture the observed seasonal correlation between summertime Southern Annular Mode (SAM) and Antarctic sea ice extentThe SAM, however, only explains 15 of the year‐to‐year sea ice extent variability in the fall, in both models and observationsSAM trends, and ozone depletion, are not the primary drivers of the observed Antarctic sea ice expansion in the last four decades [ABSTRACT FROM AUTHOR]

In spite of the unabated emissions of greenhouse gases into the atmosphere, sea ice around Antarctica has increased over most of the satellite era. Such an increase is not captured by climate models, which simulate a melting over the same period. Over the last few years, moreover, the observed sea ice trends have drastically changed, and this might act to cancel the models‐observations discrepancy. Here we show that in spite of the very recent Antarctic sea ice trend changes, such discrepancy still exists. Analyzing multiple large ensembles of model simulations, we elucidate the origin of the models‐observations discrepancy. We show that internal variability cannot account for the discrepancy, which therefore is likely to stem from biases in the models' forced response to the external forcing. These biases, we show, reside in thermodynamic ocean‐atmosphere coupling, as models fail to simulate the trends in surface heat fluxes from reanalyses over the period 1979–2019. Key Points: In spite of the Antarctic sea ice loss reported in recent years, climate models still fail to capture the observed sea ice trendThe source of discrepancy resides in the models' forced response, not in their ability to capture the internal variabilityThe models' inability to capture the observed sea ice trends is associated with a bias in simulating recent surface heat flux trends [ABSTRACT FROM AUTHOR]