The polar amplification asymmetry: Role of antarctic surface height
The polar amplification asymmetry: Role of antarctic surface height
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DOI：
10.5194/esd-8-323-2017
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发表时间：
2017-01
期刊：
影响因子：
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通讯作者：
M. Salzmann
中科院分区：
文献类型：
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作者：
M. Salzmann
抽象的。以前的研究将南极的极地放大总体上比北极弱(或慢)归因于南极表面反照率反馈较弱，也归因于南大洋更有效的海洋热吸收以及南极臭氧的消耗。本文基于低分辨率耦合气候模式中的CO2倍增实验，研究了南极地表高度对经向热量输送和包括地表反照率反馈在内的局部辐射反馈的作用。当南极洲被假定为平坦时，纬向平均大气顶辐射收支的南北不对称性显著减小。与基本模式相比，在平坦的南极洲(平坦的AA)模式中二氧化碳加倍导致南半球向极地大气和海洋的热量输送更强烈地增加。基于部分辐射扰动(PRP)的计算表明，在平坦的AA模式中，局地辐射反馈和较深大气柱中CO2强迫的增加也是导致南极变暖的原因，并对个别辐射反馈的作用进行了较详细的讨论。极放大不对称的相当大一部分(从51年开始，到126年二氧化碳倍增后，连续3个25年的时间切片在24%到80%之间)可以用地表高度的差异来解释，但这一比例受到瞬时变化的影响，在一定程度上也可能取决于模型的不确定性。为了更可靠地估计陆地高度对观测到的极地放大不对称性的影响，需要从更高分辨率的模式中进行更多基于集合的研究，并改进模式设置，使二氧化碳浓度逐渐增加。
Abstract. Previous studies have attributed an overall weaker (or slower) polar amplification in Antarctica compared to the Arctic to a weaker Antarctic surface albedo feedback and also to more efficient ocean heat uptake in the Southern Ocean in combination with Antarctic ozone depletion. Here, the role of the Antarctic surface height for meridional heat transport and local radiative feedbacks, including the surface albedo feedback, was investigated based on CO2-doubling experiments in a low-resolution coupled climate model. When Antarctica was assumed to be flat, the north–south asymmetry of the zonal mean top of the atmosphere radiation budget was notably reduced. Doubling CO2 in a flat Antarctica (flat AA) model setup led to a stronger increase in southern hemispheric poleward atmospheric and oceanic heat transport compared to the base model setup. Based on partial radiative perturbation (PRP) computations, it was shown that local radiative feedbacks and an increase in the CO2 forcing in the deeper atmospheric column also contributed to stronger Antarctic warming in the flat AA model setup, and the roles of the individual radiative feedbacks are discussed in some detail. A considerable fraction (between 24 and 80 % for three consecutive 25-year time slices starting in year 51 and ending in year 126 after CO2 doubling) of the polar amplification asymmetry was explained by the difference in surface height, but the fraction was subject to transient changes and might to some extent also depend on model uncertainties. In order to arrive at a more reliable estimate of the role of land height for the observed polar amplification asymmetry, additional studies based on ensemble runs from higher-resolution models and an improved model setup with a more realistic gradual increase in the CO2 concentration are required.