Anatomy of the Marine Ice Cliff Instability
Abstract
Ice sheets grounded on retrograde beds are susceptible to disintegration through a process called the marine ice sheet instability. This instability results from the dynamic thinning of ice near the grounding zone separating floating from grounded portions of the ice sheet. Recently a new instability called the marine ice cliff instability has been proposed. Unlike the marine ice sheet instability, the marine ice cliff instability is controlled by the brittle shear failure of ice and thus has the potential to result in much more rapid ice sheet collapse than is possible in the marine ice sheet instability. Here we explore these processes using a model where ice obeys the usual power-law creep rheology of intact ice up to a yield strength. Above the yield strength, we introduce a separate weaker rheology that incorporates quasi-brittle failure along pre-existing faults and fractures. We first tested the model by applying it to study the formation of rifts in ice shelves. These experiments shows that wide rifts localize along the shear margins and portions of the ice shelf where the stress exceeds the yield strength. These rifts decrease the buttressing capacity of the ice shelves, but can also extend to become the detachment boundary of icebergs. Next, application of the model to idealized glaciers shows that for grounded glaciers, failure localizes near the terminus in "serac" type slumping events followed by buoyant calving of the submerged portion of the glacier. Subsequently, the combination of flow and failure causes the glacier to thin towards buoyancy forming a floating ice tongue consisting of yielded ice—similar to what is currently observed at Jakobshavn Glacier in Greenland. Overall, this flexible approach to combining flow and failure yields provides a promising method of simulating the large-scale failure of glaciers and ice shelves that provides insight into both the marine-ice-cliff instability failure and rifting of ice shelves.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C33A..01B
- Keywords:
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- 0726 Ice sheets;
- CRYOSPHEREDE: 0728 Ice shelves;
- CRYOSPHEREDE: 0730 Ice streams;
- CRYOSPHEREDE: 0798 Modeling;
- CRYOSPHERE