Below is my recorded talk for the American Geophysical Union 2021 Fall Meeting. Full abstract:
Title: Process-based modeling of glacial till advection
Anders Damsgaard(1), Jan A. Piotrowski(1), Ian Madden(2), Jenny Suckale(2), Kenny K. Sørensen(3)
1: Department of Geoscience, Aarhus University, Denmark
2: Department of Geophysics, Stanford University, CA, USA
3: Department of Civil and Architectural Engineering, Aarhus University, Denmark
Glacial flow can reshape the Earth surface through erosion and deposition. Many past and present ice sheets lie on soft beds, and till mobilization and transport is governed by the degree of basal coupling, fluctuations in thermal state, subglacial hydrology, and the mechanics of the basal till itself. Changes in basal topography due to ice movement could theoretically feed back onto ice-flow dynamics. For example, the buildup of sedimentary grounding-zone wedges at the marine termini of ice streams may stabilize their position against local sea-level change. However, modeling of subglacial till advection has previously relied on fluid-like rheologies, which contrasts the now established concensus of Mohr-Coulomb plasticity.
In our work, we aim to improve the parameterization of till advection by glacial flow. We compare a new continuum model for till against laboratory consolidation and ring-shear experiments. We show how transient dynamics in porosity and strength affect the mechanics under non-steady forcings, such as glacier stick-slip or surge. We couple the till continuum model to an ice-stream model, and demonstrate how till transport varies when ice flows over simple soft-bed basal geometries, and affects ice-stream sensitivity to external forcings.
Slides and video: