Stevens Laura A, Nettles Meredith, Davis James L, Creyts Timothy T, Kingslake Jonathan, Hewitt Ian J, Stubblefield Aaron
Department of Earth Sciences, University of Oxford, Oxford, UK.
Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA.
Nat Commun. 2022 Oct 14;13(1):6065. doi: 10.1038/s41467-022-33763-2.
The flow speed of the Greenland Ice Sheet changes dramatically in inland regions when surface meltwater drains to the bed. But ice-sheet discharge to the ocean is dominated by fast-flowing outlet glaciers, where the effect of increasing surface melt on annual discharge is unknown. Observations of a supraglacial lake drainage at Helheim Glacier, and a consequent velocity pulse propagating down-glacier, provide a natural experiment for assessing the impact of changes in injected meltwater, and allow us to interrogate the subglacial hydrological system. We find a highly efficient subglacial drainage system, such that summertime lake drainage has little net effect on ice discharge. Our results question the validity of common remote-sensing approaches for inferring subglacial conditions, knowledge of which is needed for improved projections of sea-level rise.
当表层融水排入冰床时，格陵兰冰盖的流速在内陆地区会发生显著变化。但是，冰盖向海洋的排放主要由快速流动的出口冰川主导，而表层融化增加对年排放量的影响尚不清楚。对海尔海姆冰川上一个冰上湖泊排水的观测，以及随之而来的向下游传播的速度脉冲，为评估注入融水变化的影响提供了一个自然实验，并使我们能够探究冰下水文系统。我们发现了一个高效的冰下排水系统，以至于夏季湖泊排水对冰流量的净影响很小。我们的结果质疑了用于推断冰下状况的常见遥感方法的有效性，而了解冰下状况对于改进海平面上升预测是必要的。
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