Rapid fragmentation of Thwaites Eastern Ice Shelf
Rapid fragmentation of Thwaites Eastern Ice Shelf
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DOI：
10.5194/tc-16-2545-2022
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发表时间：
2022-06-27
期刊：
影响因子：
5.2
通讯作者：
Bassis, Jeremy
中科院分区：
文献类型：
--
作者：
Benn, Douglas I.;Luckman, Adrian;Bassis, Jeremy
冰架在海洋冰盖的动力学中起着关键作用，它支撑着地面冰并限制冰流入海洋的速率。为了应对最近的气候和海洋变化，西南极冰盖（WAIS）边缘的冰架已经开始破碎和退缩，对冰盖的稳定性产生重大影响。在这里，我们专注于思韦茨东冰架（TEIS），思韦茨冰川的剩余固定浮动延伸。我们发现，TEIS经历了一个破碎的过程，在过去的5年中，包括脆性破坏沿着一个主要的剪切带，形成拉伸裂缝的主体上的货架，并释放的板状冰山的东西两侧。用赫尔辛基离散元模型（HiDEM）进行的模拟表明，这种破坏模式与大陆架远缘海底钉扎点产生的高背应力有关。我们发现，一个显着的剪切区，上游的主要钉扎点，开发在2002年和2006年之间的货架，播种损害的快速加速。随后，基底熔化和损伤与应变率之间的正反馈削弱了TEIS，使损伤累积。因此，尽管随着时间的推移，TEIS上的背应力可能会随着钉扎点的缩小而减少，但损伤的积累确保了剪切带中的冰仍然是系统中最薄弱的环节。与BISICLES冰盖模型的实验表明，额外的损害或unpinning的TEIS是不太可能触发显着增加冰损失从WAIS，但产犊的响应TEIS的损失仍然是高度不确定的。人们普遍认为，冰架破碎和坍塌可能是由水力压裂和/或冰架边缘或接地点的松脱引发的。我们的研究结果表明，第三种机制，背应力引发的故障，可能会发生，如果和当冰架不再能够承受由钉扎点施加的应力。在大多数情况下，钉扎点是必不可少的冰架的稳定性，但随着冰架变薄和削弱，背应力集中在受损冰上游的钉扎点可能会提供他们的灭亡的种子。
Ice shelves play a key role in the dynamics of marine ice sheets by buttressing grounded ice and limiting rates of ice flux to the oceans. In response to recent climatic and oceanic change, ice shelves fringing the West Antarctic Ice Sheet (WAIS) have begun to fragment and retreat, with major implications for ice-sheet stability. Here, we focus on the Thwaites Eastern Ice Shelf (TEIS), the remaining pinned floating extension of Thwaites Glacier. We show that TEIS has undergone a process of fragmentation in the last 5 years, including brittle failure along a major shear zone, formation of tensile cracks on the main body of the shelf, and a release of tabular bergs on both the eastern and western flanks. Simulations with the Helsinki Discrete Element Model (HiDEM) show that this pattern of failure is associated with high backstress from a submarine pinning point at the distal edge of the shelf. We show that a significant zone of shear, upstream of the main pinning point, developed in response to the rapid acceleration of the shelf between 2002 and 2006, seeding damage on the shelf. Subsequently, basal melting and positive feedback between damage and strain rates weakened TEIS, allowing damage to accumulate. Thus, although backstress on TEIS has likely diminished over time as the pinning point shrunk, accumulation of damage has ensured that the ice in the shear zone remained the weakest link in the system. Experiments with the BISICLES ice-sheet model indicate that additional damage to or unpinning of TEIS is unlikely to trigger significantly increased ice loss from WAIS, but the calving response to the loss of TEIS remains highly uncertain. It is widely recognised that ice-shelf fragmentation and collapse can be triggered by hydrofracturing and/or unpinning from ice-shelf margins or grounding points. Our results indicate a third mechanism, backstress triggered failure, that can occur if and when an ice shelf is no longer able to withstand stress imposed by pinning points. In most circumstances, pinning points are essential for ice-shelf stability, but as ice shelves thin and weaken, the concentration of backstress in damaged ice upstream of a pinning point may provide the seeds of their demise.