Dilation of subglacial sediment governs incipient surge motion in glaciers with deformable beds

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1098/rspa.2020.0033. This is version 3 of this Preprint.

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Authors

Brent Minchew , Colin R. Meyer 

Abstract

Glacier surges are quasi-periodic episodes of rapid ice flow that arise from increases in slip-rate at the ice-bed interface. The mechanisms that trigger and sustain surges are not well-understood. Here, we develop a new model of incipient surge motion for glaciers underlain by sediments to explore how surges may arise from slip instabilities within a thin layer of saturated, deforming subglacial till. Our model represents the evolution of internal friction, porosity, and pore water pressure within the till as functions of the rate and history of shear deformation, and couples the till mechanics to a simple ice-flow model. Changes in pore water pressure govern incipient surge motion, with less-permeable till facilitating surging because dilation-driven reductions in pore-water pressure slow the rate at which till tends toward a new steady-state, thereby allowing time for the glacier to thin dynamically. The reduction of overburden (and thus effective) pressure at the bed caused by dynamic thinning of the glacier sustains surge acceleration in our model. The need for changes in both the hydromechanical properties of the till and thickness of the glacier creates restrictive conditions for surge motion that are consistent with the rarity of surge-type glaciers and their geographic clustering.

DOI

https://doi.org/10.31223/osf.io/t7xg3

Subjects

Earth Sciences, Glaciology, Physical Sciences and Mathematics

Keywords

glacier dynamics, glacier surges, granular mechanics

Dates

Published: 2020-01-22 15:08

Last Updated: 2020-05-01 21:04

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License

CC BY Attribution 4.0 International

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