title: Dynamic recrystallization during deformation of polycrystalline ice: insights from numerical simulations.
abstract: 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'.
authors.affiliation: Department of Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany maria-gema.llorens-verde@uni-tuebingen.de.|Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Maria-Gema
authors.identifier: http://orcid.org/0000-0002-6148-2600
authors.initials: MG
authors.lastname: Llorens
authors.affiliation: Departament de Geologia, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Albert
authors.initials: A
authors.lastname: Griera
authors.affiliation: Department of Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany.|Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Steinbach
authors.affiliation: Department of Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Bons
authors.affiliation: School of Geosciences, University of Aberdeen, Aberdeen, UK.
authors.forename: Enrique
authors.identifier: http://orcid.org/0000-0002-1317-6289
authors.initials: E
authors.lastname: Gomez-Rivas
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Jansen
authors.affiliation: Department of Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Roessiger
authors.affiliation: Material Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Lebensohn
authors.affiliation: Department of Geosciences, Eberhard Karls University Tübingen, Tübingen, Germany.|Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Ilka
authors.identifier: http://orcid.org/0000-0002-3023-6036
authors.initials: I
authors.lastname: Weikusat
keywords: dynamic recrystallization; ice microstructure; ice rheology; non-basal activity; strain hardening