Recent Antarctic sea-ice decline is a substantial source of concern, notably the record low in 2023 (ref. ¹). Progress has been made towards establishing the causes of ice loss^1,2,3,4,5 but uncertainty remains about its consequences for ocean–atmosphere interaction. Resolution of this uncertainty is important as ice decline can substantially alter surface heat loss and thus the ocean and atmosphere⁶. Here we show that the strongest winter 2023 ice-retraction regions provide an important new source of turbulent ocean heat loss to the atmosphere in wintertime. Ice concentration in these regions (located primarily 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. Also, there is a phase shift in the time of peak heat loss from late April to mid-June, with weaker than normal heat loss in austral autumn. The winter surface-heat-loss intensification is accompanied by substantial changes on both sides of the ocean–atmosphere interface. These include increases in atmospheric-storm frequency and surface-heat-loss-driven dense water formation, although the implications of the densification for broader processes such as Antarctic bottom water formation remain unclear. Our results reveal that the 2023 Antarctic sea-ice loss has substantially modified air–sea interaction in the Southern Ocean and motivate in-depth analysis of the wider climate-system impacts.

最近的南极海冰减少是一个令人担忧的重要问题，尤其是 2023 年的历史低点（参考文献 ¹）。在确定冰层损失的原因方面已经取得了进展^{1,2,3,4,5，但}其对海洋-大气相互作用的影响仍然存在不确定性。解决这种不确定性很重要，因为冰层消融会大大改变地表的热量损失，从而改变海洋和大气⁶。在这里，我们表明，2023 年冬季最强的冰退缩区域为冬季湍流海洋热量损失到大气中提供了重要的新来源。这些地区（主要位于威德尔海、贝灵斯豪森海和罗斯海）的冰浓度降低了 80%，并伴随着隆冬海洋热量损失的前所未有的翻倍。此外，从 4 月下旬到 6 月中旬的热量损失高峰时间存在相移，南方秋季的热量损失弱于正常情况。冬季地表热损失加剧伴随着海洋-大气界面两侧的实质性变化。这些因素包括大气风暴频率的增加和地表热损失驱动的致密水形成，尽管致密化对更广泛的过程（如南极底部水形成）的影响仍不清楚。我们的结果表明，2023 年南极海冰的消失极大地改变了南大洋的气海相互作用，并激发了对更广泛的气候系统影响的深入分析。