冰川和冰流下不断发展的基底滑动
Evolving basal slip under glaciers and ice streams
摘要：
许多快速流动的冰川和冰流在由再加工的沉积物和侵蚀产物组成的床上移动，通常被称为冰碛。冰、融水和冰碛物之间复杂的相互作用联系了冰川学中的几个基本问题，包括关于冰盖快速质量损失、冰下地貌的形成和演变以及冰下水的储存和运输的争论。现场测量已经探测了冰下床，但提供了令人惊讶的变量和似乎不一致的证据，变形发生的深度，即使在一个给定的现场。这些观察结果表明，冰下河床具有内在的动态性。本文的目标是推进我们的理解的物理过程，有助于冰下床的动力学反映在现有的观测基础变形。我们建立在最近的进展，在模拟密集，颗粒流推导出一个新的数值模型，水饱和的直到。我们的模型表明，在力平衡或水压力的时间变化的变化可以转移滑远离冰床界面和远到床，导致情节显着增强直到运输，因为整个直到层以上的深滑界面变得动员。我们比较我们的模型结果对观测的基础变形从山区冰川和冰流设置在过去和现在。我们还提出了一个分析解决方案，以评估不同的冰川环境和水力特性的冰碛物运输的变化。
英文摘要：
Many fast-flowing glaciers and ice streams move over beds consisting of reworked sediments and erosional products, commonly referred to as till. The complex interplay between ice, meltwater, and till at the subglacial bed connects several fundamental problems in glaciology including the debate about rapid mass loss from the ice sheets, the formation and evolution of subglacial landforms, and the storage and transport of subglacial water. In-situ measurements have probed the subglacial bed, but provide surprisingly variable and seemingly inconsistent evidence of the depth where deformation occurs, even at a given field site. These observations suggest that subglacial beds are inherently dynamic. The goal of this paper is to advance our understanding of the physical processes that contribute to the dynamics of subglacial beds as reflected in existing observations of basal deformation. We build on recent advances in modeling dense, granular flows to derive a new numerical model for water-saturated till. Our model demonstrates that changes in the force balance or temporal variations in water pressure can shift slip away from the ice-bed interface and far into the bed, causing episodes of significantly enhanced till transport because the entire till layer above the deep slip interface becomes mobilized. We compare our model results against observations of basal deformation from both mountain glacier and ice-stream settings in the past and present. We also present an analytical solution to assess the variability of till transport for different glacial settings and hydraulic properties.
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