Seismic-reflection evidence for a deep subglacial trough beneath Jakobshavns Isbrae, West Greenland
Seismic-reflection evidence for a deep subglacial trough beneath Jakobshavns Isbrae, West Greenland
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DOI：
10.3189/s0022143000004081
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发表时间：
1996-01-01
影响因子：
3.4
通讯作者：
Echelmeyer, K
中科院分区：
文献类型：
--
作者：
Clarke, TS;Echelmeyer, K
地震反射法被用来确定雅各布斯冰川的冰厚度和底部地形，雅各布斯冰川是格陵兰西部一个大的、快速移动的冰流/出口冰川。开发了一种数据分析方法，该方法涉及线性地震台阵和单个爆炸源数据的逐点偏移;该方法产生基底反射层的深度、水平位置和斜率。在整个界限分明的冰流之下发现了一个深U形的冰下槽。海槽向上切入基岩1500 m，其底部位于海平面以下1200-1500 m，内陆至少70 km。沿大部分通道的中线冰厚沿着约为2500 m，或约为周围冰盖的2.5倍。这个突出的基岩槽在现有的无线电回声探测数据中并不明显。反射系数表明，大部分的基底界面可能是由压实，非变形沉积物。大的冰厚度，加上相对陡峭的表面坡度，导致沿着冰流的高基底剪切应力（200-300千帕）。大的剪切应力和缺乏可变形的床意味着内部变形在雅各布港Isbrae的动力学中起着主导作用。
Seismic-reflection methods were used to determine the ice thickness and basal topography of Jakobshavns Isbrae a large, fast-moving ice stream/outlet glacier in West Greenland. A method of data analysis was developed which involves the pointwise migration of data from a linear seismic array and a single explosive source; the method yields the depth, horizontal position and slope of the basal reflector. A deep U-shaped subglacial trough was found beneath the entire length of the well-defined ice stream. The trough is incised up tc, 1500 m into bedrock, and its base lies 1200-1500 m below sea level for at least 70 km inland. Center-line ice thickness along most of the channel is about 2500 m, or about 2.5 times that of the surrounding ice sheet. This prominent bedrock trough was not apparent in existing radio-echo-sounding data. Reflection coefficients indicate that much of the basal interface is probably underlain by compacted, non-deforming sediment. The large ice thickness, coupled with relatively steep surface slopes, leads to high basal shear stresses (200-300 kPa) along the ice stream. The large shear stresses and lack of a deformable bed imply that internal deformation plays a dominant role in the dynamics of Jakobshavns Isbrae.