Modeling of deformation and recrystallisation microstructures in polar ice

Knowledge of the deformation mechanisms of polar ice is of crucial importance to predict the flow of polar ice caps and hence their influence on the global climate. Deformation of ice also impacts on one of the best climate record on Earth: the individual ice layers observed in deep ice cores. Microstructures form the main record of in situ deformation, by revealing the deformation processes that operate during the flow of an ice sheet. New microstructural analysis techniques developed at AWI now allow a much more detailed and extensive assessment of these microstructures than ever before.

Within this project, a start has been made with the numerical modelling of ice microstructures, using the comprehensive modelling platform "Elle". After updating and refining algorithms, Elle is now capable of simulating several of the main processes that occur in polar ice: recrystallisation, grain growth and crystal-plastic deformation. In the course of the project routines for two-phase materials will be adapted to model ice with bubbles or clathrates, and to model intracrystalline recovery. Results of systematic simulations will be compared quantitatively with theoretical analyses and the unique microstructure dataset available at AWI of several firn and ice cores (especially the EPICA–DML deep ice core). In particular we will critically reassess the role of grain boundary formation and migration that continually reworks the microstructure. The results of this project will improve our knowledge of the mechanical behaviour of polar ice and refine the analysis of climatic records, which are essential to ice sheet and climate modelling.



Fig.1: (a) FFT+Elle simulation of deformation of ice, compared to (b) experimentally deformed ice. Note the similarity in development of kink bands (FFT-module) and grain boundary migration (black arrows) and grain nucleation (red arrows), both simulated by Elle modules. Images kindly supplied by Griera4 and Montagnat (Grenoble)

Scientists

Paul Bons
Eberhard Karls Universität Tübingen

Sérgio H. Faria
Universität Göttingen, GZG

Sepp Kipfstuhl
AWI Bremerhaven

Jens Rößiger
Eberhard Karls Universität Tübingen

In cooperation with:
Ilka Weikhusat, AWI Bremerhaven
Albert Griera, Universitat Autònoma de Barcelona, Spain
Mark Jessell, Université de Toulouse, France
Lynn Evans, University of Melbourne, Australia

Research areas

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Publications

Rößiger J, et al., 2011. Competition between grain growth and grain size reduction in polar ice. Journal of Glaciology, in press

Rößiger J, Bons P, Griera A, Jessell M, Evans L, 2009. The effect of microstructure on grain growth rate, in particular in ice. Poster at DRT 2009 in Liverpool.

Homepage

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Research funding organisation

German Research Foundation

Project numbers: BO 1776/7
Funding period: 2009 – 2011