Modelling environmental influences on calving at Helheim Glacier in eastern Greenland
Modelling environmental influences on calving at Helheim Glacier in eastern Greenland
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DOI：
10.5194/tc-8-827-2014
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发表时间：
2014-01-01
期刊：
影响因子：
5.2
通讯作者：
James, T. D.
中科院分区：
文献类型：
--
作者：
Cook, S.;Rutt, I. C.;James, T. D.
对于世界各地的许多冰川来说，崩解是一个重要的质量损失过程，人们认为它会对各种环境影响做出反应。我们提出了一个应用于格陵兰岛东部Helheim冰川的基于物理的崩解机制的接地、流线潮水冰川模型。通过定性地检查所模拟的产犊事件的大小和频率，以及随后的动态响应，该模型被发现真实地再现了观察到的产犊行为的关键方面。实验探索了四个环境变量对冰解率的影响：裂缝中的水深、基础水压、海底融化对冰解面的底切和来自冰杂岩的背应力。在这四个变量中，只有裂缝水深和基础水压力被发现在实际应用时对末端行为有显著影响。这些结果与之前的模拟研究形成了鲜明对比，此前的模拟研究表明，海洋温度可能会强烈影响冰川融化锋面。这一结果提高了格陵兰出口冰川对格陵兰最近观察到的表面融化增加的趋势的反应比之前认为的更强烈的可能性，因为表面消融可以强烈地影响裂缝中的水深和冰川床上的水压力。
Calving is an important mass-loss process for many glaciers worldwide, and has been assumed to respond to a variety of environmental influences. We present a grounded, flowline tidewater glacier model using a physically-based calving mechanism, applied to Helheim Glacier, eastern Greenland. By qualitatively examining both modelled size and frequency of calving events, and the subsequent dynamic response, the model is found to realistically reproduce key aspects of observed calving behaviour. Experiments explore four environmental variables which have been suggested to affect calving rates: water depth in crevasses, basal water pressure, undercutting of the calving face by submarine melt and backstress from ice melange. Of the four variables, only crevasse water depth and basal water pressure were found to have a significant effect on terminus behaviour when applied at a realistic magnitude. These results are in contrast to previous modelling studies, which have suggested that ocean temperatures could strongly influence the calving front. The results raise the possibility that Greenland outlet glaciers could respond to the recent trend of increased surface melt observed in Greenland more strongly than previously thought, as surface ablation can strongly affect water depth in crevasses and water pressure at the glacier bed.