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标题：Controls on the recent speed-up of Jakobshavn Isbræ, West Greenland
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作者：C.J. Van Der Veen ; J. C. Plummer ; L.A. Stearns 等
期刊名称：Journal of Glaciology
印刷版ISSN：0022-1430
电子版ISSN：1727-5652
出版年度：2011
卷号：57
期号：204
页码：770-782
DOI：10.3189/002214311797409776
出版社：Cambridge University Press
摘要：Jakobshavn Isbræ, West Greenland, underwent a large, rapid and not well understood change in flow dynamics in 1998, leading to a doubling of its ice discharge rates. We calculate the width-averaged forces controlling flow of Jakobshavn Isbræ in 1995, 2000 and 2005 to elucidate processes responsible for this change in flow speed. In contrast to earlier suggestions, we conclude that the observed acceleration was not caused by the loss of back-stress due to weakening and subsequent break-up of the floating ice tongue alone. Gradients in longitudinal stress are small at all times considered (∼3% of the driving stress) and basal and lateral drag provide resistance to flow. Over the 10 year period considered, the average driving stress increased by 20 kPa, which was balanced by a comparable increase in lateral drag. We surmise that the velocity changes resulted from weakening of the ice in the lateral shear margins and perhaps a change in properties at the bed. Possible mechanisms for weakening of ice in the lateral shear margins include cryo-hydrologic warming of subsurface ice in the ablation zone and hydraulic weakening due to higher water content of ice in the shear margins.