The largest uncertainty in future sea-level rise is loss of ice from the Greenland and Antarctic Ice Sheets. Ice shelves, freely floating platforms of ice that fringe the ice sheets, play a crucial role in restraining discharge of grounded ice into the ocean through buttressing. However, since the 1990s, several ice shelves have thinned, retreated, and collapsed. If this pattern continues, it could expose thick cliffs that become structurally unstable and collapse in a process called marine ice cliff instability (MICI). However, the feedbacks between calving, retreat, and other forcings are not well understood. Here we review observed modes of calving from ice shelves and marine-terminating glaciers, and their relation to environmental forces. We show that the primary driver of calving is long-term internal glaciological stress, but as ice shelves thin they may become more vulnerable to environmental forcing. This vulnerability—and the potential for MICI—comes from a combination of the distribution of preexisting flaws within the ice and regions where the stress is large enough to initiate fracture. Although significant progress has been made modeling these processes, theories must now be tested against a wide range of environmental and glaciological conditions in both modern and paleo conditions. ▪ Ice shelves, floating platforms of ice fed by ice sheets, shed mass in a near-instantaneous fashion through iceberg calving. ▪ Most ice shelves exhibit a stable cycle of calving front advance and retreat that is insensitive to small changes in environmental conditions. ▪ Some ice shelves have retreated or collapsed completely, and in the future this could expose thick cliffs that could become structurally unstable called ice cliff instability. ▪ The potential for ice shelf and ice cliff instability is controlled by the presence and evolution of flaws or fractures within the ice.Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 52 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

中文翻译：

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气候变化中冰架和冰崖的稳定性


未来海平面上升的最大不确定性是格陵兰岛和南极冰盖的冰损失。冰架是冰盖边缘自由漂浮的冰平台，在抑制地面冰通过支撑流入海洋方面发挥着至关重要的作用。然而，自 20 世纪 90 年代以来，一些冰架已经变薄、后退和崩塌。如果这种模式继续下去，可能会暴露厚厚的悬崖，这些悬崖在结构上变得不稳定并在称为海洋冰崖不稳定（MICI）的过程中崩塌。然而，崩解、撤退和其他强迫之间的反馈尚不清楚。在这里，我们回顾了观察到的冰架和海洋终止冰川的崩解模式，以及它们与环境力量的关系。我们表明，冰崩解的主要驱动因素是长期的内部冰川压力，但随着冰架变薄，它们可能会更容易受到环境强迫的影响。这种脆弱性以及 MICI 的可能性是由冰内预先存在的缺陷分布以及应力大到足以引发断裂的区域共同造成的。尽管在模拟这些过程方面已经取得了重大进展，但现在必须针对现代和古条件下的各种环境和冰川条件对理论进行测试。 ▪ 冰架是由冰盖供给的浮冰平台，通过冰山崩解以近乎瞬时的方式释放质量。 ▪ 大多数冰架表现出稳定的崩解前沿前进和后退循环，对环境条件的微小变化不敏感。 ▪ 一些冰架已经后退或完全崩塌，将来可能会暴露出厚厚的悬崖，从而导致结构不稳定，称为冰崖不稳定。 ▪ 冰架和冰崖不稳定的可能性由冰内缺陷或裂缝的存在和演变控制。《地球与行星科学年度评论》第 52 卷的预计最终在线发布日期为 2024 年 5 月。请参阅 http: //www.annualreviews.org/page/journal/pubdates 了解修订后的估计。