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

• Published in: Science Advances
• Main Authors: Bradwell, Tom, Small, David, Fabel, Derek, Smedley, Rachel K., Clark, Chris D., Saher, Margot H., Callard, S. Louise, Chiverrell, Richard C., Dove, Dayton, Moreton, Steven G., Roberts, David H., Duller, Geoff A. T., Ó Cofaigh, Colm
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Nature 2019
• Subjects: Ice Sheet; Ice Shelves
• Online Access: http://nora.nerc.ac.uk/id/eprint/524611/; https://nora.nerc.ac.uk/id/eprint/524611/1/eaau1380.full.pd.pdf; https://doi.org/10.1126/sciadv.aau1380

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.