Rate-and-state friction explains glacier surge propagation

Kjetil Thøgersen,Thomas Vikhamar Schuler,Adrien Gilbert,Anders Malthe-Sørenssen

doi:10.1038/s41467-019-10506-4

Kjetil Thøgersen, Thomas Vikhamar Schuler + Show 2 more

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https://doi.org/10.1038/s41467-019-10506-4

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Journal: Nature Communications	Publication Date: Jun 27, 2019
Citations: 51	License type: open-access

Affiliation: University of Oslo

Abstract

The incomplete understanding of glacier dynamics is a major source of uncertainty in assessments of sea-level rise from land-based ice. Through increased ice discharge into the oceans, accelerating glacier flow has the potential to considerably enhance expected sea-level change, well ahead of scenarios considered by the IPCC. Central in our incomplete understanding is the motion at the glacier bed, responsible for flow transients and instabilities involving switches from slow to fast flow. We introduce a rate-and-state framework for the transient evolution of basal shear stress, which we incorporate in glacier simulations. We demonstrate that a velocity-strengthening-weakening transition combined with a characteristic length scale for the opening of subglacial cavities is sufficient to reproduce several previously unexplained features of glacier surges. The rate-and-state framework opens for new ways to analyze, understand and predict transient glacier dynamics as well as to assess the stability of glaciers and ice caps.

Highlights

The incomplete understanding of glacier dynamics is a major source of uncertainty in assessments of sea-level rise from land-based ice
We introduce a novel rate-and-state formulation for the transient evolution of basal shear stress for glaciers sliding over rigid bedrock
We demonstrate that a transition from velocitystrengthening to velocity-weakening friction combined with a characteristic length scale for the evolution of subglacial cavities is sufficient to capture the onset and propagation of glacier surges, including a traveling surface bulge, the relation between ice velocity and propagation velocity as well as the time-dependent evolution of basal shear stress

Summary

Introduction

The incomplete understanding of glacier dynamics is a major source of uncertainty in assessments of sea-level rise from land-based ice. Central in our incomplete understanding is the motion at the glacier bed, responsible for flow transients and instabilities involving switches from slow to fast flow. The rate-and-state framework opens for new ways to analyze, understand and predict transient glacier dynamics as well as to assess the stability of glaciers and ice caps. The perhaps most striking example of transient glacier dynamics is the onset and propagation of glacier surges, where ice flow velocities can increase by orders of magnitude for a period of time. Glacier surges have even been shown to act as precursors to catastrophic glacier collapse[8] In such cases it is crucial to understand what controls rapid transitions between slow and fast flow. The front of such expanding surge region is recognized as a transition from low to high surface velocities[13,14,21,22,23], and the down-glacier propagation of this front manifests as a characteristic traveling surface bulge[13]

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