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Ice-stream demise dynamically conditioned by trough shape and bed strength.

Bradwell, Tom and Small, David and Fabel, Derek and Smedley, Rachel K. and Clark, Chris C. and Saher, Margot H. and Callard, S. Louise and Chiverrell, Richard C. and Dove, Dayton and Moreton, Steven G. and Roberts, David H. and Duller, Geoff A.T. and Ó Cofaigh, Colm (2019) 'Ice-stream demise dynamically conditioned by trough shape and bed strength.', Science advances., 5 (4). eaau1380.


Ice sheet mass loss is currently dominated by fast-flowing glaciers (ice streams) terminating in the ocean as ice shelves and resting on beds below sea level. The factors controlling ice-stream flow and retreat over longer time scales (>100 years), especially the role of three-dimensional bed shape and bed strength, remain major uncertainties. We focus on a former ice stream where trough shape and bed substrate are known, or can be defined, to reconstruct ice-stream retreat history and grounding-line movements over 15 millennia since the Last Glacial Maximum. We identify a major behavioral step change around 18,500 to 16,000 years ago—out of tune with external forcing factors—associated with the collapse of floating ice sectors and rapid ice-front retreat. We attribute this step change to a marked geological transition from a soft/weak bed to a hard/strong bed coincident with a change in trough geometry. Both these factors conditioned and ultimately hastened ice-stream demise.

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Publisher statement:Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).
Date accepted:07 March 2019
Date deposited:01 May 2019
Date of first online publication:24 April 2019
Date first made open access:01 May 2019

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