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Sci Adv. 2019 Apr 24;5(4):eaau1380. doi: 10.1126/sciadv.aau1380. eCollection 2019 Apr.

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

Author information

1
Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK.
2
British Geological Survey, The Lyell Centre, Edinburgh EH14 4AP, UK.
3
Department of Geography and Planning, Durham University, Durham DH1 3LE, UK.
4
Scottish Universities Environmental Research Centre, East Kilbride, Glasgow G75 0QF, UK.
5
Department of Geography, University of Liverpool, Liverpool L69 3BX, UK.
6
Department of Geography, University of Sheffield, Sheffield S10 2TN, UK.
7
School of Ocean Sciences, Bangor University, Menai Bridge LL59 5AB, UK.
8
NERC Radiocarbon Facility, East Kilbride, Glasgow G75 0QF, UK.
9
Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth SY23 3DB, UK.

Abstract

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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