资源环境科技发展态势分析平台

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.