Ice shelf fracture is responsible for roughly half of Antarctic ice mass loss in the form of calving and can weaken buttressing of upstream ice flow. Large uncertainties associated with the ice sheet response to climate variations are due to a poor understanding of these fracture processes and how to model them. Here, we address these problems by implementing an anisotropic, nonlocal integral formulation of creep damage within a large-scale shallow-shelf ice flow model. This model can be used to study the full evolution of fracture from initiation of crevassing to rifting that eventually causes tabular calving. While previous ice shelf fracture models have largely relied on simple expressions to estimate crevasse depths, our model parameterizes fracture as a progressive damage evolution process in three-dimensions (3-D). We also implement an efficient numerical framework based on the material point method, which avoids advection errors. Using an idealized marine ice sheet, we test the creep damage model and a crevasse-depth based damage model, including a modified version of the latter that accounts for damage evolution due to necking and mass balance. We demonstrate that the creep damage model is best suited for capturing weakening and rifting over shorter (monthly/yearly) timescales, and that anisotropic damage reproduces typically observed fracture patterns better than isotropic damage. Because necking and mass balance can significantly influence damage on longer (decadal) timescales, we discuss the potential for a combined approach between models to best represent mechanical weakening and tabular calving within long-term simulations.

中文翻译：

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浅冰架广义插值质点法。 2：各向异性非局部损伤力学和裂痕传播


冰架破裂是造成南极冰块以崩解形式损失的大约一半的原因，并且会削弱上游冰流的支撑。与冰盖对气候变化的响应相关的巨大不确定性是由于对这些断裂过程以及如何对其进行建模的了解不足。在这里，我们通过在大型浅陆架冰流模型中实施蠕变损伤的各向异性、非局部积分公式来解决这些问题。该模型可用于研究裂缝从裂隙开始到裂谷最终导致板状崩解的完整演化过程。虽然以前的冰架断裂模型很大程度上依赖于简单的表达式来估计裂缝深度，但我们的模型将断裂参数化为三维（3-D）的渐进损伤演化过程。我们还实现了基于质点法的有效数值框架，避免了平流误差。使用理想化的海洋冰盖，我们测试了蠕变损伤模型和基于裂缝深度的损伤模型，包括后者的修改版本，该模型考虑了由于颈缩和质量平衡引起的损伤演化。我们证明，蠕变损伤模型最适合捕获较短（每月/每年）时间尺度内的弱化和裂痕，并且各向异性损伤比各向同性损伤更好地再现了通常观察到的断裂模式。由于颈缩和质量平衡可以显着影响较长（十年）时间尺度的损害，因此我们讨论了模型之间组合方法的潜力，以最好地代表长期模拟中的机械弱化和板状崩落。