Preprints
https://doi.org/10.5194/tc-2021-224
https://doi.org/10.5194/tc-2021-224

  17 Sep 2021

17 Sep 2021

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

Can changes in ice-sheet flow be inferred from crystallographic preferred orientations?

Maria Gema Llorens1, Albert Griera2, Paul D. Bons3,4, Ilka Weikusat3,5, David Prior6, Enrique Gomez-Rivas7, Tamara de Riese3, Ivone Jimenez-Munt1, Daniel García Castellanos1, and Ricardo A. Lebensohn8 Maria Gema Llorens et al.
  • 1Geosciencies Barcelona CSIC, Lluis Sole i Sabaris s/n, 08028 Barcelona, Spain
  • 2Departament de Geologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
  • 3Department of Geosciences, Eberhard Karls University Tübingen, Wilhemstr. 56, 72074 Tübingen, Germany
  • 4China University of Geosciences, Beijing, China
  • 5Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Germany
  • 6Department of Geology, University of Otago, 362 Leith Street, Dunedin 9016. New Zealand
  • 7Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Martí i Franquès s/n, 08028 Barcelona, Spain
  • 8Theoretical Division. Los Alamos National Laboratory. Los Alamos, NM, 87545, USA

Abstract. Creep due to ice flow is generally thought to be the main cause for the formation of crystallographic preferred orientations (CPOs) in polycrystalline anisotropic ice. However, linking the development of CPOs to the ice flow history requires a proper understanding of the ice aggregate's microstructural response to flow transitions. In this contribution the influence of ice deformation history on the CPO development is investigated by means of full-field numerical simulations at the microscale. We simulate the CPO evolution of polycrystalline ice under combinations of two consecutive deformation events up to high strain, using the code VPFFT/ELLE. A volume of ice is first deformed under co-axial boundary conditions, which results in a CPO. The sample is then subjected to different boundary conditions (co-axial or non-coaxial) in order to observe how the deformation regime switch impacts on the CPO. The model results indicate that the second flow event tends to destroy the first, inherited fabric, with a range of transitional fabrics. However, the transition is slow when crystallographic axes are critically oriented with respect to the second imposed regime. Therefore, interpretations of past deformation events from observed CPOs must be carried out with caution, particularly, in areas with complex deformation histories.

Maria Gema Llorens et al.

Status: open (until 12 Nov 2021)

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Maria Gema Llorens et al.

Model code and software

ELLE Paul D Bons, Mark W Jessell, Albert Griera, Daniel Koehn, M-G Llorens, Enrique Gomez-Rivas, Ricardo A Lebensohn, Sandra Piazolo, Florian Steinbach, Jens Becker, Jens Roessiger, Tamara de Riese, Robyn Gardner, L Evans http://elle.ws/

Maria Gema Llorens et al.

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Short summary
Polar ice is formed by ice crystals, which form fabrics that are utilized to interpret how ice sheets flow. It is not clear whether fabrics result from the current flow regime or if they are inherited. To understand to what extent ice crystals can be reoriented when the ice flow conditions change, we simulate and evaluate multi-stage ice flow scenarios according to natural cases. We find that second deformation regimes normally overprint inherited fabrics, with a range of transitional fabrics.