Am. Geophys. Union Fall Mtng: Collapse of Thwaites Eastern Ice Shelf by intersecting fractures

[eppur_se_muova]

C34A-07 - Collapse of Thwaites Eastern Ice Shelf by intersecting fractures. (Invited)

Wednesday, 15 December 2021
15:25 - 15:34
Convention Center - Room 211-213

Abstract
The Thwaites Eastern Ice Shelf (TEIS) buttresses one third of Thwaites Glacier. Removal of TEIS has the potential to increase the contribution of Thwaites Glacier to sea level rise by up to 25%. Recent research shows that the ice shelf is losing its grip on a submarine shoal that acts as a pinning point and the shear margin that separates TEIS from the Thwaites Glacier Tongue has extended, further weakening the TEIS connection to the pinning point. A sequence of Sentinel-1 radar imagery shows that parallel wing and comb cracks have recently formed rifts at high angles to the main shear margin and are propagating into the central part of the ice shelf at rates as high as 2km per year. We use satellite data, ground-penetrating radar, and GPS measurements to suggest that final collapse of Thwaites Glacier’s last remaining ice shelf may be initiated by intersection of rifts with hidden basal crevasse zones within as little as 5 years.

The central part of TEIS has no obvious surface crevasses and smooth surface topography, except for the surface expression of a pronounced basal channel aligned parallel to ice flow. Despite this smooth surface, ground-penetrating radar shows a weak zone of thin ice and complex basal topography, including numerous basal crevasses, that is not in local hydrostatic equilibrium. This local disequilibrium suggests the presence of elevated vertical shear stresses that further weaken this critical part of the ice shelf. GPS stake network observations show no measurable regional strain in the horizontal plane because large-scale flow is being accommodated by the lateral shear margin.

In the near future, the propagating rifts are likely to intersect this weak zone, triggering rifting along the basal crevasses and, subsequently, along the basal channel and a into secondary set of basal crevasses on the eastern side of the basal channel. This ``zigzag’’ rift sequence would disconnect the main flow from the influence of the pinning point (and compressive arches) and will ultimately lead to a complete disintegration of the ice shelf.



Plain-language Summary
The Thwaites Eastern Ice Shelf is the floating terminus of the Thwaites Glacier, one of the fastest changing glaciers in Antarctica and contributing as much as 4% of global sea level rise today. This floating ice shelf is stabilized offshore by a marine shoal and acts as a dam to slow the flow of ice off the continent into the ocean. If this floating ice shelf breaks apart, the Thwaites Glacier will accelerate and its contribution to sea level rise will increase by as much as 25%. Over the last several years, satellite radar imagery shows many new fractures opening up. Similar to a growing crack in the windshield of a car, a slowly growing crack means the windshield is weak and a small bump to the car might cause the windshield to suddenly break apart into hundreds of panes of glass. We have mapped out weaker and stronger areas of the ice shelf and suggest a “zig-zag” pathway the fractures might take through the ice, ultimately leading to break up of the shelf in as little as 5 years, which result in more ice flowing off the continent.

First Author
P
Erin C Pettit
Oregon State University
Authors
W
Christian Wild
Oregon State University
A
Karen Alley
University of Manitoba
M
Atsuhiro Muto
The Pennsylvania State University
T
Martin Truffer
University of Alaska Fairbanks
B
Suzanne Louise Bevan
Swansea University
B
Jeremy N Bassis
University of Michigan
C
Anna Crawford
University of St Andrews
S
Ted A Scambos
University of Colorado, Boulder
B
Doug Benn
University of St Andrews

Scientific Team
ITGC TARSAN Team