Can unconfined ice shelves provide buttressing via hoop stresses?
Can unconfined ice shelves provide buttressing via hoop stresses?
复制标题
无约束冰架可以通过环向应力提供支撑吗？
DOI：
10.1017/jog.2019.101
复制
发表时间：
2020
影响因子：
3.4
通讯作者：
Worster, M. Grae
中科院分区：
文献类型：
--
作者：
Wearing, Martin G.;Kingslake, Jonathan;Worster, M. Grae
冰架内的应力平衡是阻力或支撑力的关键，它可以提供并部分控制上游冰盖的冰排放速率。人们普遍认为，无约束冰架不提供支撑。然而，理论和实验室规模的模拟实验表明，无侧限，浮动粘性流通过环向应力产生扶壁。环向应力是由粘性阻力引起的，在发散流中，粘性阻力对垂直于流动方向的扩散起作用。我们建立在理论工作，探索环向应力扶壁的大小的控制，推导出扶壁随着有效粘度的增加和增加的发散。我们使用一个理想化的模型校准到南极冰架的无限制部分，发现许多货架有效粘度低，最有可能是由于高拉伸应力造成的广泛损害。因此，它们不能承受抵抗流动所需的大的环向应力。一些全年被海冰包围的冰架具有更大的有效粘度，可以提供支撑，这表明海冰减少了断裂。然而，我们发现，大多数无侧限冰架提供微不足道的扶壁今天，即使环向应力被认为是在应力平衡。
The stress balance within an ice shelf is key to the resistance, or buttressing, it can provide and in part controls the rate of ice discharge from the upstream ice sheet. Unconfined ice shelves are widely assumed to provide no buttressing. However, theory and laboratory-scale analogue experiments have shown that unconfined, floating viscous flows generate buttressing via hoop stresses. Hoop stress results from the viscous resistance to spreading perpendicular to the flow direction in a diverging flow. We build on theoretical work to explore the controls on the magnitude of hoop-stress buttressing, deducing that buttressing increases with increasing effective viscosity and increasing divergence. We use an idealised model calibrated to unconfined sections of Antarctic ice shelves and find that many shelves have low effective viscosity, most likely due to extensive damage resulting from high extensional stresses. Therefore, they are unable to sustain the large hoop stresses required to resist flow. Some ice shelves that are surrounded by sea ice year-round have a greater effective viscosity and can provide buttressing, suggesting that sea ice reduces fracturing. However, we find that most unconfined ice shelves provide insignificant buttressing today, even when hoop stresses are considered in the stress balance.
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