Surface undulations of Antarctic ice streams tightly controlled by bedrock topography
Surface undulations of Antarctic ice streams tightly controlled by bedrock topography
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DOI：
10.5194/tc-7-407-2013
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
J. Rydt;G. Gudmundsson;H. Corr;P. Christoffersen
中科院分区：
文献类型：
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作者：
J. Rydt;G. Gudmundsson;H. Corr;P. Christoffersen
Full Stokes流线模型预测，快速流动的冰流将基岩地形的信息最有效地传递到地表，其长度尺度在平均冰厚的1到20倍之间。这种典型的行为与流动规律和滑动规律指数的精确值无关，应该是普遍可见的。然而，迄今为止还没有获得这一重要理论预测的实验证据，因此忽略了对当前冰流模式物理有效性的重要检验。在我们的工作中，我们使用了最近获得的Rutford冰流和Evans冰流的机载雷达数据，我们表明，快速流动的冰的表面响应对基岩不规则性非常敏感，波长为几个冰厚。灵敏度取决于滑动比，即平均基底滑动速度与平均变形速度之比。我们发现，较高的滑移比值通常会导致更有效的传递，而对于通过蠕变获得大部分表面速度的冰来说，传递会受到显著的抑制。我们的研究结果强调了基岩地形对冰流动力学在20倍于平均冰厚的空间尺度上的重要性。我们的研究结果还表明，在这个空间尺度上，流动形式和地表地形的局部变化不能用基底滑性的变化来解释。
Full Stokes flow-line models predict that fast-flowing ice streams transmit information about their bedrock topography most efficiently to the surface for basal undulations with length scales between 1 and 20 times the mean ice thickness. This typical behaviour is independent of the precise values of the flow law and sliding law exponents, and should be universally observable. However, no experimental evidence for this important theoretical prediction has been obtained so far, hence ignoring an important test for the physical validity of current-day ice flow models. In our work we use recently acquired airborne radar data for the Rutford Ice Stream and Evans Ice Stream, and we show that the surface response of fast-flowing ice is highly sensitive to bedrock irregularities with wavelengths of several ice thicknesses. The sensitivity depends on the slip ratio, i.e. the ratio between mean basal sliding velocity and mean deformational velocity. We find that higher values of the slip ratio generally lead to a more efficient transfer, whereas the transfer is significantly dampened for ice that attains most of its surface velocity by creep. Our findings underline the importance of bedrock topography for ice stream dynamics on spatial scales up to 20 times the mean ice thickness. Our results also suggest that local variations in the flow regime and surface topography at this spatial scale cannot be explained by variations in basal slipperiness.