6 Title: Process-based modeling of glacial till advection
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8 Anders Damsgaard(1), Jan A. Piotrowski(1), Ian Madden(2), Jenny Suckale(2), Kenny K. Sørensen(3)
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10 1: Department of Geoscience, Aarhus University, Denmark
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12 2: Department of Geophysics, Stanford University, CA, USA
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14 3: Department of Civil and Architectural Engineering, Aarhus University, Denmark
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16 Glacial flow can reshape the Earth surface through erosion and
17 deposition. Many past and present ice sheets lie on soft beds, and till
18 mobilization and transport is governed by the degree of basal coupling,
19 fluctuations in thermal state, subglacial hydrology, and the mechanics of
20 the basal till itself. Changes in basal topography due to ice movement
21 could theoretically feed back onto ice-flow dynamics. For example,
22 the buildup of sedimentary grounding-zone wedges at the marine termini
23 of ice streams may stabilize their position against local sea-level
24 change. However, modeling of subglacial till advection has previously
25 relied on fluid-like rheologies, which contrasts the now established
26 concensus of Mohr-Coulomb plasticity.
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28 In our work, we aim to improve the parameterization of till advection by
29 glacial flow. We compare a new continuum model for till against laboratory
30 consolidation and ring-shear experiments. We show how transient dynamics
31 in porosity and strength affect the mechanics under non-steady forcings,
32 such as glacier stick-slip or surge. We couple the till continuum model
33 to an ice-stream model, and demonstrate how till transport varies when
34 ice flows over simple soft-bed basal geometries, and affects ice-stream
35 sensitivity to external forcings.