The Role of Natural Versus Forced Change in Future Rapid Summer Arctic Ice Loss
The Role of Natural Versus Forced Change in Future Rapid Summer Arctic Ice Loss
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自然变化与强迫变化在未来夏季北极冰层快速流失中的作用
DOI：
10.1029/180gm10
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
D. Bailey
中科院分区：
文献类型：
--
作者：
M. Holland;C. Bitz;L. Tremblay;D. Bailey
来自共同体气候系统模式第三版（CCSM 3）的气候模式模拟表明，北极海冰可能在21世纪经历快速的9月冰撤退。先前的一项研究表明，这是由于海冰变薄到更脆弱的条件，海洋热量输送以脉冲式增加的形式出现“反冲”，以及加速退缩的正反馈。在这里，我们进一步研究影响这些事件的因素，包括自然与强迫变化的作用和模拟海冰覆盖的阈值样行为的可能性。我们发现几乎没有迹象表明，一个临界海冰状态达到，然后导致快速冰损失。相反，我们的研究结果表明，快速的冰损失事件是由于人为的变化，不断增长的内在变异性加强。世纪由于冰盖变薄，夏季冰面积的自然变率增加。随着冰层变薄，大片地区很容易融化，导致冰层范围发生相当大的变化。在模拟的快速冰损失的自然变化的重要作用是这样的，我们发现很少有能力预测这些事件的基础上，以前的冰和海洋条件的知识。这是支持的敏感性模拟的结果在事件发生前几年，表现出很少的预测能力。
Climate model simulations from the Community Climate System Model, version 3 (CCSM3) suggest that Arctic sea ice could undergo rapid September ice retreat in the 21 st century. A previous study indicated that this results from a thinning of sea ice to more vulnerable conditions, a "kick" in the form of pulse-like increases in ocean heat transport and positive feedbacks that accelerate the retreat. Here we further examine the factors affecting these events, including the role of natural versus forced change and the possibility of threshold-like behavior in the simulated sea ice cover. We find little indication that a critical sea ice state is reached that then leads to rapid ice loss. Instead, our results suggest that the rapid ice loss events result from anthropogenic change reinforced by growing intrinsic variability. The natural variability in summer ice extent increases in the 21st century because of the thinning ice cover. As the ice thins, large regions can easily melt out, resulting in considerable ice extent variations. The important role of natural variability in the simulated rapid ice loss is such that we find little capability for predicting these events based on a knowledge of prior ice and ocean conditions. This is supported by results from sensitivity simulations initialized several years prior to an event, which exhibit little predictive skill.