Preprints
https://doi.org/10.5194/tc-2021-81
https://doi.org/10.5194/tc-2021-81

  31 Mar 2021

31 Mar 2021

Review status: this preprint is currently under review for the journal TC.

Geometric Controls of Tidewater Glacier Dynamics

Thomas Frank1,2, Henning Åkesson3,4, Basile de Fleurian1, Mathieu Morlighem5, and Kerim H. Nisancioglu1,6 Thomas Frank et al.
  • 1Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
  • 2Department of Physical Geography, Stockholm University, Sweden
  • 3Department of Geological Sciences, Stockholm University, Sweden
  • 4Bolin Centre for Climate Research, Stockholm, Sweden
  • 5Department of Earth System Science, University of California, Irvine, USA
  • 6Centre for Earth Evolution and Dynamics, University of Oslo, Oslo, Norway

Abstract. Retreat of marine outlet glaciers often initiates depletion of inland ice through dynamic adjustments of the upstream glacier. The local topography of a fjord may promote or inhibit such retreat, and therefore fjord geometry constitutes a critical control on ice sheet mass balance. To quantify the processes of ice-topography interactions and enhance the understanding of the dynamics involved, we analyze a multitude of topographic fjord settings and scenarios using the Ice-sheet and Sea-level System Model (ISSM). We systematically study glacier retreat through a variety of artificial fjord geometries and quantify the modeled dynamics directly in relation to topographic features. We find that retreat in an upstream widening or deepening fjord does not necessarily promote retreat, but conversely, may stabilize a glacier because converging ice flow towards a constriction enhances lateral shear. An upstream narrowing or shoaling fjord, in turn, may promote retreat since fjord walls or bed provide little stability to the glacier where ice flow diverges. Furthermore, we identify distinct quantitative relationships directly linking grounding line discharge and retreat rate to fjord topography, and transfer these results to a long-term study of the retreat of Jakobshavn Isbræ. These findings offer new perspectives on ice-topography interactions, and give guidance to an ad-hoc assessment of future topographically induced ice loss based on knowledge of the upstream fjord geometry.

Thomas Frank et al.

Status: open (until 26 May 2021)

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Thomas Frank et al.

Thomas Frank et al.

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Short summary
The shape of a fjord can promote or inhibit glacier retreat in response to climate change. We conduct experiments with a synthetic setup under idealized conditions in a numerical model to study and quantify the processes involved. We find that friction between ice and fjord is the most important factor, and that it is possible to directly link ice discharge and grounding line retreat to fjord topography in a quantitative way.