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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 2
The Cryosphere, 8, 587-605, 2014
https://doi.org/10.5194/tc-8-587-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
The Cryosphere, 8, 587-605, 2014
https://doi.org/10.5194/tc-8-587-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Apr 2014

Research article | 08 Apr 2014

Fracture-induced softening for large-scale ice dynamics

T. Albrecht2,1 and A. Levermann2,1 T. Albrecht and A. Levermann
  • 1Earth System Analysis, Potsdam Institute for Climate Impact Research, Potsdam, Germany
  • 2Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany

Abstract. Floating ice shelves can exert a retentive and hence stabilizing force onto the inland ice sheet of Antarctica. However, this effect has been observed to diminish by the dynamic effects of fracture processes within the protective ice shelves, leading to accelerated ice flow and hence to a sea-level contribution. In order to account for the macroscopic effect of fracture processes on large-scale viscous ice dynamics (i.e., ice-shelf scale) we apply a continuum representation of fractures and related fracture growth into the prognostic Parallel Ice Sheet Model (PISM) and compare the results to observations. To this end we introduce a higher order accuracy advection scheme for the transport of the two-dimensional fracture density across the regular computational grid. Dynamic coupling of fractures and ice flow is attained by a reduction of effective ice viscosity proportional to the inferred fracture density. This formulation implies the possibility of non-linear threshold behavior due to self-amplified fracturing in shear regions triggered by small variations in the fracture-initiation threshold. As a result of prognostic flow simulations, sharp across-flow velocity gradients appear in fracture-weakened regions. These modeled gradients compare well in magnitude and location with those in observed flow patterns. This model framework is in principle expandable to grounded ice streams and provides simple means of investigating climate-induced effects on fracturing (e.g., hydro fracturing) and hence on the ice flow. It further constitutes a physically sound basis for an enhanced fracture-based calving parameterization.

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