Interhemispheric coupling, the West Antarctic Ice Sheet and warm Antarctic interglacials
Interhemispheric coupling, the West Antarctic Ice Sheet and warm Antarctic interglacials
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DOI：
10.5194/cp-6-431-2010
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发表时间：
2010-07
影响因子：
4.3
通讯作者：
P. Holden;N. Edwards;E. Wolff;N. Lang;J. Singarayer;P. Valdes;T. Stocker
中科院分区：
文献类型：
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作者：
P. Holden;N. Edwards;E. Wolff;N. Lang;J. Singarayer;P. Valdes;T. Stocker
抽象的。冰芯证据表明，尽管在过去80万年的任何时间点大气中的CO2浓度都没有超过约300 ppm，但在最近四次间冰期中，南极洲东部至少比工业化前（CO2约280 ppm）高出约3-4 °C。在前三个间冰期，这种异常变暖是短暂的（约3000年），显然发生在北方半球冰消作用完成之前。在下文中，我们将这些时期称为“比当前瞬变更温暖”（WPT）。通过一系列实验研究了冰消期融水对大西洋经向翻转环流（AMOC）和南极温度的影响。众所周知，减缓的AMOC将通过双极跷跷板增加南部海表温度（SST），观测数据表明，AMOC在WPT之前的整个终止期间保持较弱，在与南极温度峰值密切一致的时间迅速加强。我们提出了两个800 kyr的瞬态模拟使用中间复杂性模型GENIE-1，这表明，融水强迫产生短暂的南部变暖，是一致的WPT的时间，但不足以（在这个单一的参数化）重现所观察到的温暖的幅度。为了研究模型和边界条件的不确定性，我们提出了三个合奏的瞬态GENIE-1模拟跨终端II（135 000至124 000 BP）和三个快照HadCM 3模拟在130 000 BP。只有考虑到西南极冰盖（WAIS）退缩的可能反馈，才有可能模拟观测到的变暖幅度。
Abstract. Ice core evidence indicates that even though atmospheric CO2 concentrations did not exceed ~300 ppm at any point during the last 800 000 years, East Antarctica was at least ~3–4 °C warmer than preindustrial (CO2~280 ppm) in each of the last four interglacials. During the previous three interglacials, this anomalous warming was short lived (~3000 years) and apparently occurred before the completion of Northern Hemisphere deglaciation. Hereafter, we refer to these periods as "Warmer than Present Transients" (WPTs). We present a series of experiments to investigate the impact of deglacial meltwater on the Atlantic Meridional Overturning Circulation (AMOC) and Antarctic temperature. It is well known that a slowed AMOC would increase southern sea surface temperature (SST) through the bipolar seesaw and observational data suggests that the AMOC remained weak throughout the terminations preceding WPTs, strengthening rapidly at a time which coincides closely with peak Antarctic temperature. We present two 800 kyr transient simulations using the Intermediate Complexity model GENIE-1 which demonstrate that meltwater forcing generates transient southern warming that is consistent with the timing of WPTs, but is not sufficient (in this single parameterisation) to reproduce the magnitude of observed warmth. In order to investigate model and boundary condition uncertainty, we present three ensembles of transient GENIE-1 simulations across Termination II (135 000 to 124 000 BP) and three snapshot HadCM3 simulations at 130 000 BP. Only with consideration of the possible feedback of West Antarctic Ice Sheet (WAIS) retreat does it become possible to simulate the magnitude of observed warming.