Dynamic patterns of ice stream flow in a 3-D higher-order ice sheet model with plastic bed and simplified hydrology
Dynamic patterns of ice stream flow in a 3-D higher-order ice sheet model with plastic bed and simplified hydrology
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DOI：
10.1029/2011jf002025
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发表时间：
2011-11-04
影响因子：
3.9
通讯作者：
Payne, A. J.
中科院分区：
文献类型：
--
作者：
Bougamont, M.;Price, S.;Payne, A. J.
由于冰流的复杂流动，预测冰盖质量平衡具有挑战性。为了解决这个问题，我们耦合了一个三维高阶冰盖模型的基础过程模型，冰下直到有塑性流变和不断变化的屈服应力。该模型进行了测试，其敏感性区域水的可用性。首先，假设不排水床，冰流之间的振荡活动和停滞阶段，仅仅作为一个结果，热力学反馈发生在冰，直到界面。然而，随着时间的推移，速度幅度降低，因为不充足的基础融水导致冰流逐渐融化，并进入一个缓慢流动的“冰盖模式。“第二，我们假设冰碛能够从假设的区域水文系统中吸收水。这导致了显着不同的长期行为，因为持续振荡的“冰流模式”得以维持。冰碛层中额外的水导致更高的速度，引发冰和冰碛层之间更强的热力学反馈。结果还表明，快速流动的冰流可能会调制直到属性作为一个结果的持续时间的热条件在前面的停滞阶段。同样地，停滞冰流下的冰碛物特性也受到前一个快速流动阶段的基础条件的影响。我们的研究结果支持的推断，冰流的强烈影响的存在下，区域水文系统，强调需要准确地描述冰动态，基础条件和区域冰下水文冰盖模型之间的耦合。
Predicting ice sheet mass balance is challenging because of the complex flow of ice streams. To address this issue, we have coupled a three-dimensional higher-order ice sheet model to a basal processes model where subglacial till has a plastic rheology and evolving yield stress. The model was tested for its sensitivity to regional water availability. First, with an assumed undrained bed, the ice stream oscillates between active and stagnant phases, solely as a result of thermodynamic feedbacks occurring at the ice-till interface. However, the velocity amplitude decreases over time, as insufficient basal meltwater causes the ice stream to gradually thicken and enter a slow flowing "ice sheet mode." Second, we assume that the till is able to assimilate water from a hypothetical regional hydrological system. This leads to significantly different long-term behavior, as a continuously oscillating "ice stream mode" is maintained. The extra water incorporated in the till leads to higher velocities, triggering stronger thermodynamic feedbacks between the ice and till layer. Results also suggest that fast-flowing ice streams may be modulated by till properties as a result of the duration of thermal conditions during the preceding stagnant phase. Similarly, till properties beneath stagnant ice streams are influenced by basal conditions during the preceding fast flow phase. Our findings support the inference that ice streams are strongly influenced by the presence of a regional hydrological system, underscoring the need to accurately describe the coupling between ice dynamics, basal conditions and regional subglacial hydrology in ice sheet models.