Record Low Winter 2023 Antarctic Sea-Ice Increased Ocean Heat Loss, Dense Water Formation and Storms

The recent decline in Antarctic sea-ice, notably the extreme low winter cover in 2023 and 2024 is a major source of concern. Some progress has been made towards determining the drivers of ice loss but uncertainty remains regarding its impacts, particularly for ocean-atmosphere interaction. Resolution of this uncertainty is important as ice decline can significantly modify surface heat loss, and thus the ocean and atmosphere. We show that the substantial failure of ice regrowth in winter 2023 provided a major new source of turbulent ocean heat loss to the atmosphere. Ice concentration in the Weddell, Bellingshausen and Ross Seas is reduced by up to 80% and is accompanied by an unprecedented doubling of mid-winter ocean heat loss. Furthermore, peak heat loss shifts from late April to mid-June with weaker than normal heat loss in austral autumn. The strengthening of winter surface heat loss is accompanied by changes on both sides of the ocean-atmosphere interface. These include a rise in frequency of atmospheric storms and greater surface heat loss driven dense water formation. The findings reveal that the record low winter 2023 Antarctic sea-ice cover substantially modified Southern Ocean-atmosphere interaction and motivate in-depth analysis of the wider climate system impacts. The subsequent evolution of low ice conditions together with their ocean-atmosphere impacts through to 2025 will also be considered.