Arctic Sea Ice in Two Configurations of the CESM2 During the 20th and 21st Centuries
Arctic Sea Ice in Two Configurations of the CESM2 During the 20th and 21st Centuries
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DOI：
10.1029/2020jc016133
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发表时间：
2020-09-01
影响因子：
3.6
通讯作者：
Smith, Abigail
中科院分区：
文献类型：
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作者：
DeRepentigny, Patricia;Jahn, Alexandra;Smith, Abigail
我们对共同体地球系统模型第2版(CESM2)模拟的北极海冰的当前和未来状态进行了评估。CESM2是为耦合模式比较项目(CMIP6)第六阶段作出贡献的CESM版本。我们分析了两种具有不同大气成分的CESM2配置中北极海冰覆盖的变化：CESM2(CAM6)和CESM2(WACCM6)。在历史时段内，CESM2(CAM6)冬季冰层厚度分布偏薄，导致夏季冰层面积低于CESM2(WACCM6)和观测值。在两种CESM2配置中，第一次无冰条件的时间与CMIP6未来排放情景的选择不敏感。事实上，只有当全球变暖保持在1.5摄氏度以下时，北极夏季无冰的可能性才会很低，而CMIP6的任何一种情景都不会实现这一点。到21世纪末，与之前的版本相比，CESM2模拟了秋季几个月的海洋热损失减少，推迟了海冰的形成，并导致高排放情景下的无冰条件长达8个月。结果，两种CESM2配置都显示出冬季和春季冰面积的加速下降，这是以前在CESM模拟中未曾见过的行为。气候敏感性的差异和到2100年在CMIP6高排放情景下大气CO(2)水平高于其CMIP5模拟情景，可以解释为什么CESM以前没有模拟今年冬天的冰损失。
We provide an assessment of the current and future states of Arctic sea ice simulated by the Community Earth System Model version 2 (CESM2). The CESM2 is the version of the CESM contributed to the sixth phase of the Coupled Model Intercomparison Project (CMIP6). We analyze changes in Arctic sea ice cover in two CESM2 configurations with differing atmospheric components: the CESM2(CAM6) and the CESM2(WACCM6). Over the historical period, the CESM2(CAM6) winter ice thickness distribution is biased thin, which leads to lower summer ice area compared to CESM2(WACCM6) and observations. In both CESM2 configurations, the timing of first ice-free conditions is insensitive to the choice of CMIP6 future emissions scenario. In fact, the probability of an ice-free Arctic summer remains low only if global warming stays below 1.5 degrees C, which none of the CMIP6 scenarios achieve. By the end of the 21st century, the CESM2 simulates less ocean heat loss during the fall months compared to its previous version, delaying sea ice formation and leading to ice-free conditions for up to 8 months under the high emissions scenario. As a result, both CESM2 configurations exhibit an accelerated decline in winter and spring ice area, a behavior that had not been previously seen in CESM simulations. Differences in climate sensitivity and higher levels of atmospheric CO(2)by 2100 in the CMIP6 high emissions scenario compared to its CMIP5 analog could explain why this winter ice loss was not previously simulated by the CESM.