Dynamic recrystallization during deformation of polycrystalline ice: insights from numerical simulations

The flow of glaciers and polar ice sheets is controlled by the highly anisotropic rheology of ice crystals that have hexagonal symmetry (ice lh). To improve our knowledge of ice sheet dynamics, it is necessary to understand how dynamic recrystallization (DRX) controls ice microstructures and rheolog...

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Published in:Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences physical, and engineering sciences, 2017-02, Vol.375 (2086), p.20150346-20150346
Main Authors: Llorens, Maria-Gema, Griera, Albert, Steinbach, Florian, Bons, Paul D., Gomez-Rivas, Enrique, Jansen, Daniela, Roessiger, Jens, Lebensohn, Ricardo A., Weikusat, Ilka
Format: Article
Language:English
Subjects:
Boundary conditions
Computer simulation
Deformation
Deformation mechanisms
Dynamic Recrystallization
Glaciers
Ice crystals
Ice Microstructure
Ice Rheology
Ice sheets
Localization
Maxima
Non-Basal Activity
Plastic deformation
Recrystallization
Rheological properties
Rheology
Shear
Simulation
Slip
Strain Hardening
Strain rate
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Summary:The flow of glaciers and polar ice sheets is controlled by the highly anisotropic rheology of ice crystals that have hexagonal symmetry (ice lh). To improve our knowledge of ice sheet dynamics, it is necessary to understand how dynamic recrystallization (DRX) controls ice microstructures and rheology at different boundary conditions that range from pure shear flattening at the top to simple shear near the base of the sheets. We present a series of two-dimensional numerical simulations that couple ice deformation with DRX of various intensities, paying special attention to the effect of boundary conditions. The simulations show how similar orientations of c-axis maxima with respect to the finite deformation direction develop regardless of the amount of DRX and applied boundary conditions. In pure shear this direction is parallel to the maximum compressional stress, while it rotates towards the shear direction in simple shear. This leads to strain hardening and increased activity of non-basal slip systems in pure shear and to strain softening in simple shear. Therefore, it is expected that ice is effectively weaker in the lower parts of the ice sheets than in the upper parts. Strain-rate localization occurs in all simulations, especially in simple shear cases. Recrystallization suppresses localization, which necessitates the activation of hard, non-basal slip systems. This article is part of the themed issue ‘Microdynamics of ice’.
ISSN:1364-503X
1471-2962
DOI:10.1098/rsta.2015.0346