Arctic and Antarctic Sea Ice Mean State in the Community Earth System Model Version 2 and the Influence of Atmospheric Chemistry
Arctic and Antarctic Sea Ice Mean State in the Community Earth System Model Version 2 and the Influence of Atmospheric Chemistry
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DOI：
10.1029/2019jc015934
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发表时间：
2020-08-01
影响因子：
3.6
通讯作者：
Bailey, David A.
中科院分区：
文献类型：
--
作者：
DuVivier, Alice K.;Holland, Marika M.;Bailey, David A.
随着气候的变化，北极和南极的海冰发生了重大而迅速的变化。在这里，我们介绍了来自新发布的社区地球系统模型版本2 （CESM2）的工业化前和历史结果，以评估北极和南极的海冰。CESM2有两种配置，不同之处在于它们的大气模式顶和包含全面的大气化学，包括预测气溶胶。具有综合大气化学的CESM2配置显示北极海冰全年显著变厚，并且更好地捕捉到海冰范围和体积在卫星周期内的减少趋势。在南极，两种CESM配置具有相似的平均状态冰范围和体积，但冰范围趋势与卫星观测相反。我们发现，北极海冰在CESM2配置之间的差异是液态云差异的结果。在北极上空，没有预估气溶胶形成的CESM2构型使较少的气溶胶形成云凝结核，导致更薄的液体云。因此，海冰在融化季节早期接收到更多的短波辐射，推动了更强的冰反照率反馈，导致额外的海冰损失和全年明显变薄的冰。形成北极液态云所必需的气溶胶是由不同的前体排放物产生并输送到北极的。因此，北极海冰差异的主要原因是影响云的气溶胶向该地区的输送，而南极相对而言仍未受到极外气溶胶输送的影响。随着气候的变化，北极和南极的海冰发生了显著而迅速的变化。在这里，我们评估北极和南极海冰在一个新的最先进的地球系统模型，社区地球系统模型版本2 （CESM2）。特别是，我们探索大气是如何影响海冰的。当CESM2模型不包括大气中粒子的化学成分时，我们发现北极的云层更薄，这使得更多的阳光能够在春夏两季到达表面的海冰。结果，海冰融化得更快，覆盖北冰洋表面的面积更小，总体上比CESM2模拟中更薄。CESM2模拟中确实包含了颗粒的化学成分。相比之下，颗粒化学的包含或缺乏并不会导致南极海冰厚度或海冰覆盖面积的大差异。在半球产生相反结果的原因是，影响云层的粒子是在北极和南极之外产生的。这些粒子被成功地运送到北极，但南极仍然相对原始，不受外部粒子运输的影响。
Arctic and Antarctic sea ice has undergone significant and rapid change with the changing climate. Here, we present preindustrial and historical results from the newly released Community Earth System Model Version 2 (CESM2) to assess the Arctic and Antarctic sea ice. Two configurations of the CESM2 are available that differ only in their atmospheric model top and the inclusion of comprehensive atmospheric chemistry, including prognostic aerosols. The CESM2 configuration with comprehensive atmospheric chemistry has significantly thicker Arctic sea ice year-round and better captures decreasing trends in sea ice extent and volume over the satellite period. In the Antarctic, both CESM configurations have similar mean state ice extent and volume, but the ice extent trends are opposite to satellite observations. We find that differences in the Arctic sea ice between CESM2 configurations are the result of differences in liquid clouds. Over the Arctic, the CESM2 configuration without prognostic aerosol formation has fewer aerosols to form cloud condensation nuclei, leading to thinner liquid clouds. As a result, the sea ice receives much more shortwave radiation early in the melt season, driving a stronger ice albedo feedback and leading to additional sea ice loss and significantly thinner ice year-round. The aerosols necessary for the Arctic liquid cloud formation are produced from different precursor emissions and transported to the Arctic. Thus, the main reason sea ice differs in the Arctic is the transport of cloud-impacting aerosols into the region, while the Antarctic remains relatively pristine from extrapolar aerosol transport.Plain Language Summary Arctic and Antarctic sea ice has undergone significant and rapid change with the changing climate. Here we assess Arctic and Antarctic sea ice in a new state-of-the-art Earth System Model, the Community Earth System Model Version 2 (CESM2). In particular, we explore how the atmosphere impacts the sea ice. When the CESM2 model does not include chemistry of particles in the atmosphere, we find that Arctic clouds are thinner, which allows more sunlight to reach the sea ice at the surface in the spring and summer. As a result, the sea ice melts more so that it covers less of the Arctic Ocean surface and is overall thinner than in CESM2 simulations that do include chemistry of particles. In contrast, inclusion or lack of particle chemistry does not lead to large differences in the Antarctic sea ice thickness or surface area covered by sea ice. The reason for the opposite results in the hemispheres is that the particles that impact clouds are produced outside the Arctic and Antarctic. These particles are transported successfully to the Arctic, but the Antarctic remains relatively pristine from external particle transport.