ERL Special Talk: Luke Zoet (University of Wisconsin)
Wednesday, October 24, 2018 at 3:00pm to 4:00pm
Building 54, 209
21 AMES ST, Cambridge, MA 02139
Processes of glacial slip over a deformable bed
Constitutive rules exist in various forms for glacier slip over a deformable substrate. Although experiments have generally shown that till behaves as a Coulomb material, in most models deformable beds are treated as viscous or viscoplastic fluids. In order to examine processes at the ice-bed interface, experiments have been conducted using a large diameter ring-shear device capable of sliding an annulus of ice with an outer diameter of 90 cm over a deformable till bed. These experiments have been used to explore the fundamental processes active at the ice-bed interface and better constrain glacier slip. Results indicate that a deformable bed exhibits rate dependence over a small range of shear stress values less than the yield strength of the till. At shear stresses equal to the yield strength, the bed shears in a thin layer near the ice-bed interface with resistance independent of slip velocity. During periods of stationary contact, the ice-bed interface strengthens logarithmically with time as the real area of contact between the ice and bed increases. These results provide the first experimental guidance for flow models that seek to include the combined effects of ice and till mechanics in a constitutive rule for basal slip.