Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice
Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice
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DOI：
10.1098/rspa.2011.0422
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发表时间：
2012-04-08
影响因子：
3.5
通讯作者：
Walker, C. C.
中科院分区：
文献类型：
--
作者：
Bassis, J. N.;Walker, C. C.
观测结果表明，海洋终端区冰盖和冰川的动态变化与产犊引起的终端区位置变化密切相关。然而，对产犊过程本身的了解仍然很少，而且在目前的数值冰盖模式中没有很好地参数化。在本研究中，我们通过使用两个互补模型，推导出海洋终止冰川崩解面最大稳定冰厚的合理上限和下限，从而解决了这种不确定性。第一个模型假设拉伸和剪切破坏的结合可以使靠近终点的冰崖不稳定和/或使已有的裂缝相交。该模型的一个直接后果是，厚冰川必须终止于深水区以稳定产冰前沿，从而产生一个预测的最大冰崖高度，该高度随着水深的增加而增加，这与从西格陵兰岛、南极洲、斯瓦尔巴群岛和阿拉斯加冰川中收集的观测结果一致。第二个模型考虑了一个类似的下限，假设冰已经破裂，裂缝由孔隙压力润滑。在该模型中，只有当进入末端区的冰相对完整，且没有预先存在的深穿透裂缝时，才能形成浮动冰舌。
Observations indicate that substantial changes in the dynamics of marine-terminating ice sheets and glaciers are tightly coupled to calving-induced changes in the terminus position. However, the calving process itself remains poorly understood and is not well parametrized in current numerical ice sheet models. In this study, we address this uncertainty by deriving plausible upper and lower limits for the maximum stable ice thickness at the calving face of marine-terminating glaciers, using two complementary models. The first model assumes that a combination of tensile and shear failure can render the ice cliff near the terminus unstable and/or enable pre-existing crevasses to intersect. A direct consequence of this model is that thick glaciers must terminate in deep water to stabilize the calving front, yielding a predicted maximum ice cliff height that increases with increasing water depth, consistent with observations culled from glaciers in West Greenland, Antarctica, Svalbard and Alaska. The second model considers an analogous lower limit derived by assuming that the ice is already fractured and fractures are lubricated by pore pressure. In this model, a floating ice tongue can only form when the ice entering the terminus region is relatively intact with few pre-existing, deeply penetrating crevasses.