Crawford Anna J, Benn Douglas I, Todd Joe, Åström Jan A, Bassis Jeremy N, Zwinger Thomas
School of Geography and Sustainable Development, University of St Andrews, St Andrews, UK.
School of GeoSciences, The University of Edinburgh, Edinburgh, UK.
Nat Commun. 2021 May 11;12(1):2701. doi: 10.1038/s41467-021-23070-7.
Marine ice-cliff instability could accelerate ice loss from Antarctica, and according to some model predictions could potentially contribute >1 m of global mean sea level rise by 2100 at current emission rates. Regions with over-deepening basins >1 km in depth (e.g., the West Antarctic Ice Sheet) are particularly susceptible to this instability, as retreat could expose increasingly tall cliffs that could exceed ice stability thresholds. Here, we use a suite of high-fidelity glacier models to improve understanding of the modes through which ice cliffs can structurally fail and derive a conservative ice-cliff failure retreat rate parameterization for ice-sheet models. Our results highlight the respective roles of viscous deformation, shear-band formation, and brittle-tensile failure within marine ice-cliff instability. Calving rates increase non-linearly with cliff height, but runaway ice-cliff retreat can be inhibited by viscous flow and back force from iceberg mélange.
海洋冰崖失稳可能加速南极洲的冰流失，根据一些模型预测，按照当前的排放速率，到2100年可能使全球平均海平面上升超过1米。深度超过1千米的盆地过度加深的区域（如西南极冰盖）尤其容易受到这种失稳的影响，因为冰盖退缩可能会露出越来越高的冰崖，而这些冰崖可能会超过冰的稳定阈值。在这里，我们使用一套高保真冰川模型来增进对冰崖结构破坏模式的理解，并为冰盖模型推导一个保守的冰崖破坏退缩速率参数化。我们的结果突出了粘性变形、剪切带形成和脆性拉伸破坏在海洋冰崖失稳中的各自作用。崩解速率随冰崖高度呈非线性增加，但粘性流动和来自冰山混合体的反向力可以抑制冰崖的失控退缩。
