Rapid fragmentation of Thwaites Eastern Ice Shelf
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Published:2022-06-27
Issue:6
Volume:16
Page:2545-2564
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Benn Douglas I., Luckman AdrianORCID, Åström Jan A., Crawford Anna J.ORCID, Cornford Stephen L.ORCID, Bevan Suzanne L.ORCID, Zwinger ThomasORCID, Gladstone RupertORCID, Alley Karen, Pettit ErinORCID, Bassis Jeremy
Abstract
Abstract. 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.
Funder
Natural Environment Research Council Academy of Finland
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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