AMOC Stability and Diverging Response to Arctic Sea Ice Decline in Two Climate Models
AMOC Stability and Diverging Response to Arctic Sea Ice Decline in Two Climate Models
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DOI：
10.1175/jcli-d-20-0572.1
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发表时间：
2021-07-01
影响因子：
4.9
通讯作者：
Liu, Wei
中科院分区：
文献类型：
--
作者：
Li, Hui;Fedorov, Alexey;Liu, Wei
本文在两种不同水平分辨率的共同体地球系统模式中，比较了北极海冰减少对大西洋纬向翻转环流（AMOC）的影响。在一系列模型实验中，我们在冰面上施加辐射不平衡，复制了与1979-2014年期间观察到的海冰覆盖损失，我们发现两个模型之间的AMOC响应存在显着差异。在较低分辨率的配置中，AMOC在前100年减弱了约三分之一，接近新的准平衡。相比之下，在更高分辨率的配置，AMOC减弱了类似的10%，在第一个20-30年，随后在拉布拉多海和邻近地区的深水形成的膨胀驱动的全面复苏。我们调查这些差异，使用诊断AMOC稳定性指标，这反映了AMOC淡水运输进出流域，因此流域尺度盐平流反馈的强度。这一指标表明，AMOC在较低分辨率的模式是不太稳定，更敏感的表面扰动，证实了模拟北极淡水化由于海冰下降的冲洗实验。模型的平均状态之间的差异，包括大西洋平均表面淡水通量，控制AMOC稳定性的差异。我们的研究结果表明，AMOC稳定性指标确实是有用的评估AMOC扰动的敏感性。我们强调，尽管在长期调整的差异，这两个模型模拟了一个几十年的AMOC减弱引起的北极海冰下降，相关的气候变化。
This study compares the impacts of Arctic sea ice decline on the Atlantic meridional overturning circulation (AMOC) in two configurations of the Community Earth System Model with different horizontal resolution. In a suite of model experiments, we impose radiative imbalance at the ice surface, replicating a loss of sea ice cover comparable to that observed during 1979-2014, and we find dramatic differences in the AMOC response between the two models. In the lower-resolution configuration, the AMOC weakens by about one-third over the first 100 years, approaching a new quasi-equilibrium. By contrast, in the higher-resolution configuration, the AMOC weakens by similar to 10% during the first 20-30 years followed by a full recovery driven by invigorated deep water formation in the Labrador Sea and adjacent regions. We investigate these differences using a diagnostic AMOC stability indicator, which reflects the AMOC freshwater transport in and out of the basin and hence the strength of the basin-scale salt-advection feedback. This indicator suggests that the AMOC in the lower-resolution model is less stable and more sensitive to surface perturbations, as confirmed by hosing experiments mimicking Arctic freshening due to sea ice decline. Differences between the models' mean states, including the Atlantic Ocean mean surface freshwater fluxes, control the differences in AMOC stability. Our results demonstrate that the AMOC stability indicator is indeed useful for evaluating AMOC sensitivity to perturbations. We emphasize that, despite the differences in the long-term adjustment, both models simulate a multidecadal AMOC weakening caused by Arctic sea ice decline, relevant to climate change.