[DLS] Jeremy Brooks (UW- Madison)

“A Glacier Slip Law Incorporating Debris-Bed Friction”

Fast-flowing glaciers primarily move by slip at their base. Ice-sheet models use a “slip law” which relates slip velocity to other variables. The chosen form of the slip law strongly affects predictions of ice-sheet mass loss and future sea-level rise. Despite decades of research, there is no agreement on which form of the slip law is appropriate. Slip laws assume that ice at the base of the glacier is “clean” (without rock debris), but observations suggest that it is “dirty” (debris- or sediment-rich) in most glacial environments. Here, we investigate the influence of debris-rich basal ice on the physics of glacier slip using laboratory experiments and numerical ice-flow models. We conduct experiments under realistic glaciological conditions to directly quantify the slip law, finding that debris-bed friction increases the magnitude of basal drag and alters the functional form of the slip law compared to clean ice conditions. We propose a new slip law incorporating debris-bed friction, and validate this slip law using ice-flow model simulations conducted using realistic rough glacier bed topography. Then, we conduct large-scale ice-sheet model simulations using the debris-bed friction slip law. Results suggest that incorporating debris-bed friction can substantially affect predictions of ice-sheet retreat, but the magnitude of the effect is largely dependent on poorly-constrained parameter values. To improve predictions of sea-level rise, future work is needed to characterize the physical conditions at the ice-bed interface, which will inform the choice of the slip law used in ice-sheet models.

EAPS Department Lecture Series —

Weekly talks aimed to bring together the entire EAPS community, given by leading thinkers in the areas of geology, geophysics, geobiology, geochemistry, atmospheric science, oceanography, climatology, and planetary science. Runs concurrently with class 12.S501.

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