EGU23-12553, updated on 26 Feb 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

At the bottom of ice streams: unraveling the physics of sliding onset through a glacier-scale field experiment

Elisa Mantelli1, Reinhard Drews2, Olaf Eisen3, Daniel Farinotti4, Martin Luethi5, Laurent Mingo6, Dustin Schroeder7, and Andreas Vieli5
Elisa Mantelli et al.
  • 1University of Tasmania, IMAS, Australia (
  • 2Department of Geosciences, University of Tübingen, Tübingen, Germany
  • 3Alfred Wegener Institute, Bremerhaven, Germany
  • 4VAW, ETH Zürich, Zürich, Switzerland
  • 5Department of Geography, University of Zurich, Zurich, Switzerland
  • 6Blue System Integration Ltd., Vancouver, Canada
  • 7Departments of Geophysics and Electrical Engineering, Stanford University, Stanford (CA), USA

Fast ice stream flow at speeds of hundreds to thousands of meters per year is sustained by sliding at the ice sheet base, whereas slow flow outside of ice streams is characterized by limited-to-no basal sliding. In this sense, the transition from no sliding to significant sliding exerts a key control on ice stream flow. The detailed physical processes that enable the onset of basal sliding are somewhat debated, but laboratory experiments, recent theoretical work, and a handful of direct observations support the notion of sliding initiating below the melting point as a result of regelation and premelting. 

In this contribution we describe a recently funded glacier-scale field experiment that has been designed to advance the understanding of sliding onset physics by testing the hypothesis that sliding starts below the melting point. The experiment will take place at the Grenzgletscher (Swiss Alps), which is known to have a cold-based accumulation region and a temperate-based ablation region. Our work will involve extensive surface geophysics (radio echo sounding, terrestrial radar interferometry, radar thermal tomography) aimed at identifying the sliding onset region. This work will guide the site selection for a subsequent borehole study of englacial deformation that is meant illuminate the relation between sliding velocity and basal temperature. The borehole work will allow us to test systematically the hypothesis that sliding starts below the melting point through an extended region of temperature-dependent sliding, and possibly to advance the formulation of temperature-dependent friction laws that are used to describe the onset of sliding in ice flow models.

The focus of this contribution will be specifically on the experimental design - how it is informed by existing theory and observations, and how it will support theoretical and ice flow modeling advances, at the glacier scale and beyond.

How to cite: Mantelli, E., Drews, R., Eisen, O., Farinotti, D., Luethi, M., Mingo, L., Schroeder, D., and Vieli, A.: At the bottom of ice streams: unraveling the physics of sliding onset through a glacier-scale field experiment, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-12553,, 2023.