Abstract The persistence of below normal Antarctic sea ice extent (SIE) since 2017 after decades of decline possibly suggests a new Antarctic sea ice regime, from largely wind-driven variability prior to 2015, with more oceanic influence after 2015. To investigate this further, here we make use of a large ensemble of seasonal Antarctic SIE reconstructions calibrated during 1979-2020, before many of the observed record lows. Since these reconstructions are primarily based on atmospheric predictor variables, examining their performance in recent years (2021-2023) helps to better understand the potential for a new Antarctic sea ice state and more robustly assess the skill of these reconstructions. When calibrated to observations from 1979-2023, overall the reconstruction model performs only slightly lower than the original version, and generally remains stationary through time. However, there are marked regional disparities in model performance when predicting the recent extremes using the original reconstruction model, whereby the reconstruction only reliably captures these anomalies in the Bellingshausen and Weddell Seas. The continued predictive power and model performance across much of West Antarctica compared to East Antarctica suggests the possibility of a continued wind-driven role across much of West Antarctica for recent extremes, and a stronger oceanic thermodynamic role in much of East Antarctica. Finally, while the reconstructions rarely produce negative Antarctic SIE anomalies as low as observed in winter 2023, the reconstruction model does indicate in these cases connections to a strong tropically-driven component, at least partially consistent with recent observed changes in the Ross Sea.
Sartori et al. (Wed,) studied this question.