Subglacial sediment flux

Collaborators: Luke Zoet (advisor), Natasha Morgan-Witts, Anders Damsgaard, Jenny Suckale, Ian Madden, John Menzies, Kasia Warburton, Peter Sobel, Neal Lord

Rapid motion of many glaciers and ice streams occurs by ice sliding over soft sediment beds. This sediment moves in response to stress exerted by the overriding ice, influencing rates of erosion and generating subglacial landforms over a range of timescales. Many questions surround the physical processes that control this deformation due to the difficulty of studying it directly in the field. I tackle this uncertainty with my collaborators by simulating glacier slip in the lab with a custom cryogenic ring shear apparatus. I use a variety of techniques, including image processing to track sediment motion and detailed analysis of the sediment micromorphology and fabric, to link the deformation in the till bed to specific glaciological controls. Results from these experiments are being used to inform numerical models of subglacial sediment flux coupled to an ice sheet flow model.

Sediment deformation during glacier slip in a cryogenic ring shear experiment.

Grain displacements estimated from a photographic time series of deforming till bed

Schematic and images of the cryo-ring shear device
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Freeze-on of subglacial sediments

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Estimating subglacial effective pressure with active seismics