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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/tc-2018-212
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2018-212
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 Nov 2018

Research article | 07 Nov 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).

Buoyant forces promote tidewater glacier iceberg calving through large basal stress concentrations

Matt Trevers1, Antony J. Payne1, Stephen L. Cornford1,2, and Twila Moon3 Matt Trevers et al.
  • 1Centre for Polar Observation and Modelling, School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
  • 2Department of Geography, Swansea University, Swansea, SA2 8PP, UK
  • 3National Snow and Ice Data Center, University of Colorado, Boulder, CO 80309-0449 USA

Abstract. Iceberg calving parameterisations currently implemented in ice sheet models do not reproduce the full observed range of calving behaviours. For example, though buoyant forces at the ice front are known to trigger full-depth calving events on major Greenland outlet glaciers, a multi-stage iceberg calving event at Jakobshavn Isbræ is unexplained by existing models. To explain this and similar events, we propose a notch-triggered rotation mechanism whereby a relatively small subaerial calving event triggers a larger full-depth calving event due to the abrupt increase in buoyant load and the associated stresses generated at the ice-bed interface. We investigate the notch-triggered rotation mechanism by applying a geometric perturbation to the subaerial section of the calving front in a diagnostic flowline model of an idealised glacier snout, using the full-Stokes, finite element method code Elmer/Ice. Different sliding laws and water pressure boundary conditions are applied at the ice-bed interface. Water pressure has a big influence on the likelihood of calving, and stress concentrations large enough to open crevasses were generated in basal ice. Significantly, the location of stress concentrations produced calving events of approximately the size observed, providing support for future application of the notch-triggered rotation mechanism in ice-sheet models.

Matt Trevers et al.
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Latest update: 15 Nov 2018
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Short summary
Iceberg calving is a major factor in the retreat of outlet glaciers of the Greenland Ice Sheet. Massive block overturning calving events occur at major outlet glaciers. A major calving event 2009 was triggered by the release of a smaller block of ice from above the waterline. Using a numerical model, we investigate the feasibility of this mechanism to drive large calving events. We find that relatively small perturbations induce forces large enough to open cracks in ice at the glacier bed.
Iceberg calving is a major factor in the retreat of outlet glaciers of the Greenland Ice Sheet....
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