Marine Ice Cliff Instability Mitigated by Slow Removal of Ice Shelves
Marine Ice Cliff Instability Mitigated by Slow Removal of Ice Shelves
复制标题
DOI：
10.1029/2019gl084183
复制
发表时间：
2019-11-11
影响因子：
5.2
通讯作者：
Behn, Mark D.
中科院分区：
文献类型：
--
作者：
Clerc, Fiona;Minchew, Brent M.;Behn, Mark D.
支撑南极冰盖的冰架加速崩解可能形成不稳定的冰崖。海洋冰崖不稳定性假说认为，高于临界高度（如90米）的悬崖将发生结构崩塌，在冰盖模型中引发失控退缩。这个临界高度是根据先前存在的静态冰崖推断出来的。在这里，我们展示了临界高度如何随着冰架崩塌的时间尺度而增加。我们模拟了冰架支撑应力去除后冰崖变形的破坏机制。如果移除发生迅速，即使在相对较小的悬崖高度，悬崖也会主要发生弹性变形，并通过拉脆断裂破坏。随着冰架移动时间尺度的增加，黏性松弛作用占主导地位，在大于d的时间尺度上，临界高度增加到540 m左右。90米的临界高度意味着冰架将在一小时内被移除。在预测冰盖模型中纳入冰架崩塌时间尺度将减轻海洋冰崖的不稳定性，这意味着较少的冰质量损失。
The accelerated calving of ice shelves buttressing the Antarctic Ice Sheet may form unstable ice cliffs. The marine ice cliff instability hypothesis posits that cliffs taller than a critical height (similar to 90 m) will undergo structural collapse, initiating runaway retreat in ice-sheet models. This critical height is based on inferences from preexisting, static ice cliffs. Here we show how the critical height increases with the timescale of ice-shelf collapse. We model failure mechanisms within an ice cliff deforming after removal of ice-shelf buttressing stresses. If removal occurs rapidly, the cliff deforms primarily elastically and fails through tensile-brittle fracture, even at relatively small cliff heights. As the ice-shelf removal timescale increases, viscous relaxation dominates, and the critical height increases to similar to 540 m for timescales greater than days. A 90-m critical height implies ice-shelf removal in under an hour. Incorporation of ice-shelf collapse timescales in prognostic ice-sheet models will mitigate the marine ice cliff instability, implying less ice mass loss.