The representation of iceberg calving in numerical models is a key source of uncertainty in century-scale sea-level rise projections. Parameters central to model representations of calving, including the tensile strength of glacier ice, remain poorly constrained. Grain-size and sample-size dependence make it difficult to reconcile laboratory and in situ estimates of ice tensile strength. Further, assumptions of various numerical models obscure comparison of the ‘strength’ parameter with a physically observable value. Here, we address the problem of fracture during calving using an analogous natural laboratory: a viscoelastic analysis of observed surface deformation and associated stresses in the 2015 collapse of eastern Skaftá cauldron, Vatnajökull ice cap, Iceland. We find that the ice within the cauldron could have experienced instantaneous elastic stress on the order of several MPa. We observe surface crevasses at the cauldron edges and center, but find that large areas of ice remain intact despite high stress. Our findings suggest a tensile strength of glacier ice on the order of 1 MPa, consistent with laboratory estimates but exceeding previous glacier-specific estimates.

中文翻译：

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从冰岛瓦特纳冰川冰盖 2015 年东部斯卡夫塔大锅坍塌的观测中推断出的冰川冰的拉伸强度

数值模型中冰山崩塌的表示是世纪尺度海平面上升预测中不确定性的关键来源。对产犊模型表示的核心参数，包括冰川冰的拉伸强度，仍然受到很差的约束。粒度和样本大小的依赖性使得难以协调实验室和现场对冰抗张强度的估计。此外，各种数值模型的假设模糊了“强度”参数与物理可观察值的比较。在这里，我们使用类似的自然实验室解决了产犊过程中的断裂问题：对 2015 年冰岛瓦特纳冰川冰盖东部斯卡夫塔大锅坍塌中观察到的表面变形和相关应力的粘弹性分析。我们发现，大锅内的冰可能经历了数 MPa 量级的瞬时弹性应力。我们观察到大锅边缘和中心的表面裂缝，但发现尽管压力很大，大面积的冰仍然完好无损。我们的研究结果表明，冰川冰的抗拉强度约为 1 MPa，与实验室估计一致，但超过了先前的冰川特定估计。