Abstract. Sea-ice cover over the Southern Ocean responds to and impacts Southern Ocean dynamics and, thus, mid to high latitude climate in the Southern Hemisphere. In addition, sea-ice cover can significantly modulate the carbon exchange between the atmosphere and the ocean. As climate models are the only tool available to project future climate changes, it is important to assess their performance in simulating past changes. The Last Glacial Maximum (LGM, ∼21,000 years ago) represents an interesting target as it is a relatively well documented period with climatic conditions and a carbon cycle very different from pre-industrial conditions. Here, we study the changes in seasonal Antarctic sea-ice cover as simulated in numerical PMIP3 and LOVECLIM simulations of the LGM, and their relationship with windstress and ocean temperature. Simulations and paleo-proxy records suggest a fairly well constrained glacial winter sea-ice edge at 51.5° S (1 sigma range: 50°–55.5° S). Simulated glacial summer sea-ice cover however differs widely between models, ranging from almost no sea ice to a sea-ice edge reaching 55.5° S. The austral summer multi-model mean sea-ice edge lies at ∼60.5° S (1 sigma range: 57.5°–70.5° S). Given the lack of strong constraints on the summer sea-ice edge based on sea-ice proxy records, we extend our model-data comparison to summer sea-surface temperature. Our analysis suggests that the multi-model mean summer sea ice provides a reasonable, albeit upper end, estimate of the austral summer sea-ice edge allowing us to conclude that the multi-model mean of austral summer and winter sea-ice cover seem to provide good estimates of LGM conditions. Using these best estimates, we find that there was a larger sea-ice seasonality during the LGM compared to the present day.

中文翻译：

---

从最后一次冰川最大值评估南部海洋的季节性海冰覆盖率

摘要。南大洋的海冰覆盖响应并影响了南大洋的动力，因此影响了南半球的中高纬度气候。此外，海冰的覆盖可以显着调节大气与海洋之间的碳交换。由于气候模型是预测未来气候变化的唯一可用工具，因此评估其在模拟过去变化中的性能非常重要。上一次冰期最高期（LGM，约21,000年前）代表了一个有趣的目标，因为这是一个相对有据可查的时期，其气候条件和碳循环与工业化前的条件截然不同。在这里，我们研究了LGM的PMIP3和LOVECLIM数值模拟中模拟的南极季节性海冰盖变化及其与风应力和海洋温度的关系。模拟和古代理记录表明，在51.5°S（1 sigma范围：50°-55.5°S），冰川冬季海冰边缘受到了很好的约束。但是，不同模型之间模拟的冰川夏季海冰覆盖范围差异很大，范围从几乎没有海冰到达到55.5°S的海冰边缘。夏季南方多模式平均海冰边缘位于〜60.5°S（1 sigma范围：57.5°–70.5°S）。鉴于基于海冰代理记录的夏季海冰边缘缺乏严格的约束，我们将模型数据比较扩展到夏季海表温度。我们的分析表明，多模式均值夏季海冰提供了合理的，尽管是南极夏季海冰边缘的估计值，但可以使我们得出结论，夏季和冬季南极海冰覆盖率的多模式均值似乎可以提供良好的LGM条件估计。