We assess Antarctic sea ice climatology and variability in version 2 of the Community Earth System Model (CESM2) and compare it to that in the older CESM1 and (where appropriate) real‐world observations. In CESM2, Antarctic sea ice is thinner and less extensive than in CESM1, though sea ice area is still approximately 1 million km² greater in CESM2 than in present‐day observations. Though there is less Antarctic sea ice in CESM2, the annual cycle of ice growth and melt is more vigorous in CESM2 than in CESM1. A new mushy layer thermodynamics formulation implemented in the latest version of the Community Ice Code (CICE) in CESM2 accounts for both greater frazil ice formation in coastal polynyas and more snow‐to‐ice conversion near the edge of the ice pack in the new model. Greater winter ice divergence in CESM2 (relative to CESM1) is due to stronger stationary wave activity and greater wind stress curl over the ice pack. Greater wind stress curl, in turn, drives more warm water upwelling under the ice pack, thinning it and decreasing its extent. Overall, differences between Antarctic sea ice in CESM2 and CESM1 arise due to both differences in their sea ice thermodynamics formulations and differences in their coupled atmosphere‐ocean states.

中文翻译：

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社区地球系统模型版本2中的南极海冰概述，第一部分：海冰热力学和大气-海洋-冰雪过程耦合下的季节周期分析

我们评估了社区地球系统模型（CESM2）第2版中的南极海冰气候学和变异性，并将其与较旧的CESM1和（在适当情况下）实际观测中的南极海冰气候学和变异性进行了比较。在CESM2中，南极海冰比CESM1中的海冰更薄且范围更小，尽管海冰面积仍约为100万公里^2。CESM2中的数据要比今天的观察结果大。尽管CESM2的南极海冰较少，但CESM2的冰增长和融化的年循环比CESM1更为活跃。在CESM2的最新版本的《社区冰规则》（CICE）中实施的一种新的糊状层热力学公式，说明了沿岸多尼亚人中更多的巴西冰形成和新模型中冰袋边缘附近的冰雪转化更多。CESM2（相对于CESM1）的冬季冰散度更大是由于更强的驻波活动和更大的冰袋上的风应力卷曲。反过来，更大的风应力卷曲会驱使更多的热水在冰袋下上升，使其变薄并减小其程度。全面的，