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Speaker: Luke Zoet, Associate Professor, Department of Geosciences, University of Wisconsin- Madison

Host: Ginny Catania

Title: Determining how glaciers deform their beds

Abstract: Many fast-moving glaciers move atop beds made of deformable sediments (till), and deformation of these subglacial sediments during basal slip shapes the beds and regulates glacier flow. The resultant sediment flux impacts glacier dynamics and rates of subglacial erosion over a range of timescales, but its fundamental dependencies are not well understood. Using a cryogenic ring shear device, we conducted experiments to investigate the effects of both effective stress and slip speed on rates of till transport. We find a near-linear relationship between sediment flux and slip speed, but a non-monotonic, double-valued dependency of sediment flux on effective stress. Deformation primarily occurred in a thin shear band near the ice sole, the thickness of which could vary with both parameters.