The Last Interglacial period (LIG) is a period with increased summer insolation at high northern latitudes, which results in strong changes in the terrestrial and marine cryosphere. Understanding the mechanisms for this response via climate modelling and comparing the models' representation of climate reconstructions is one of the objectives set up by the Paleoclimate Modelling Intercomparison Project for its contribution to the sixth phase of the Coupled Model Intercomparison Project. Here we analyse the results from 16 climate models in terms of Arctic sea ice. The multi-model mean reduction in minimum sea ice area from the pre industrial period (PI) to the LIG reaches 50 % (multi-model mean LIG area is 3.20×10⁶ km², compared to 6.46×10⁶ km² for the PI). On the other hand, there is little change for the maximum sea ice area (which is 15–16×10⁶ km² for both the PI and the LIG. To evaluate the model results we synthesise LIG sea ice data from marine cores collected in the Arctic Ocean, Nordic Seas and northern North Atlantic. The reconstructions for the northern North Atlantic show year-round ice-free conditions, and most models yield results in agreement with these reconstructions. Model–data disagreement appear for the sites in the Nordic Seas close to Greenland and at the edge of the Arctic Ocean. The northernmost site with good chronology, for which a sea ice concentration larger than 75 % is reconstructed even in summer, discriminates those models which simulate too little sea ice. However, the remaining models appear to simulate too much sea ice over the two sites south of the northernmost one, for which the reconstructed sea ice cover is seasonal. Hence models either underestimate or overestimate sea ice cover for the LIG, and their bias does not appear to be related to their bias for the pre-industrial period. Drivers for the inter-model differences are different phasing of the up and down short-wave anomalies over the Arctic Ocean, which are associated with differences in model albedo; possible cloud property differences, in terms of optical depth; and LIG ocean circulation changes which occur for some, but not all, LIG simulations. Finally, we note that inter-comparisons between the LIG simulations and simulations for future climate with moderate (1 % yr⁻¹) CO₂ increase show a relationship between LIG sea ice and sea ice simulated under CO₂ increase around the years of doubling CO₂. The LIG may therefore yield insight into likely 21st century Arctic sea ice changes using these LIG simulations.

中文翻译：

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127 ka北极海冰的多模型CMIP6-PMIP4研究：海冰数据汇编和模型差异

上一次冰期间期（LIG）是北部高纬度地区夏季日照增加的时期，这会导致陆地和海洋冰冻圈发生强烈变化。通过气候建模了解这种响应的机制并比较模型对气候重建的表示，是古气候建模比对项目为对耦合模型比对项目的第六阶段做出的贡献而设立的目标之一。在这里，我们根据北极海冰分析了16种气候模型的结果。从工业化前阶段（PI）到LIG的最小海冰面积的多模型平均减少量达到50％（LIG的多模型平均面积为3.20 ×10 ⁶  km ²，而6.46 ×10 ⁶PI为 km ²）。另一方面，最大海冰面积（15–16 ×10 ⁶  km ²对于PI和LIG。为了评估模型结果，我们从北冰洋，北欧海和北大西洋北部收集的海芯中综合了LIG海冰数据。北大西洋北部的重建显示全年无冰，大多数模型得出的结果与这些重建一致。在格陵兰附近和北冰洋边缘的北欧海中，在模型数据方面存在分歧。按时间顺序排列的最北端站点，即使在夏季也要重建大于75％的海冰浓度，因此可以区分那些模拟过少的海冰的模型。但是，剩余的模型似乎在最北端的两个站点上模拟了太多的海冰，因此重建的海冰覆盖是季节性的。因此，LIG的模型要么被低估要么被高估，并且它们的偏差似乎与工业化前时期的偏差无关。模型间差异的驱动因素是北冰洋上短波异常上下相位的不同阶段，这与模型反照率的差异有关。就光学深度而言，可能存在的云特性差异；LIG海洋环流的变化发生在某些（但不是全部）LIG模拟中。最后，我们注意到，LIG模拟与中度（1％年）未来气候模拟之间的相互比较 模型间差异的驱动因素是北冰洋上下短波异常的不同阶段，这与模型反照率的差异有关；就光学深度而言，可能存在的云特性差异；LIG海洋环流的变化发生在某些（但不是全部）LIG模拟中。最后，我们注意到，LIG模拟与中度（1％年）未来气候模拟之间的相互比较 模型间差异的驱动因素是北冰洋上下短波异常的不同阶段，这与模型反照率的差异有关；就光学深度而言，可能存在的云特性差异；LIG海洋环流的变化发生在某些（但不是全部）LIG模拟中。最后，我们注意到，LIG模拟与中度（1％年）未来气候模拟之间的相互比较^-1）CO ₂增加显示下CO模拟LIG海冰和海冰之间的关系₂围绕翻一番CO的增加₂。因此，利用这些LIG模拟，LIG可能会深入了解21世纪北极海冰的变化。