Bell Robin E, Studinger Michael, Shuman Christopher A, Fahnestock Mark A, Joughin Ian
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964-8000, USA.
Nature. 2007 Feb 22;445(7130):904-7. doi: 10.1038/nature05554.
Water plays a crucial role in ice-sheet stability and the onset of ice streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence ice-sheet dynamics are unknown, however, and large subglacial lakes have not been closely associated with rapidly flowing ice streams. Here we use satellite imagery and ice-surface elevations to identify a region of subglacial lakes, similar in total area to Lake Vostok, at the onset region of the Recovery Glacier ice stream in East Antarctica and predicted by ice-sheet models. We define four lakes through extensive, flat, featureless regions of ice surface bounded by upstream troughs and downstream ridges. Using ice velocities determined using interferometric synthetic aperture radar (InSAR), we find the onset of rapid flow (moving at 20 to 30 m yr(-1)) of the tributaries to the Recovery Glacier ice stream in a 280-km-wide segment at the downslope margins of these four subglacial lakes. We conclude that the subglacial lakes initiate and maintain rapid ice flow through either active modification of the basal thermal regime of the ice sheet by lake accretion or through scouring bedrock channels in periodic drainage events. We suggest that the role of subglacial lakes needs to be considered in ice-sheet mass balance assessments.
水在冰盖稳定性和冰流形成过程中起着至关重要的作用。冰下湖水在湖泊之间流动并迅速排泄，引发灾难性洪水。然而，冰下湖泊影响冰盖动力学的确切机制尚不清楚，而且大型冰下湖泊与快速流动的冰流并没有紧密联系。在此，我们利用卫星图像和冰面高程，在东南极洲复苏冰川冰流的起始区域识别出一个冰下湖泊区域，其总面积与沃斯托克湖相似，且该区域是由冰盖模型预测出来的。我们通过由上游低谷和下游山脊界定的广阔、平坦、无特征的冰面区域定义了四个湖泊。利用干涉合成孔径雷达（InSAR）测定的冰流速，我们发现在这四个冰下湖泊下坡边缘280公里宽的区域内，复苏冰川冰流支流出现了快速流动（流速为20至30米/年）。我们得出结论，冰下湖泊通过湖泊堆积对冰盖底部热状态进行主动改造，或通过周期性排水事件冲刷基岩河道，从而启动并维持冰的快速流动。我们建议在冰盖质量平衡评估中需要考虑冰下湖泊的作用。
