Competition between grain growth and grain-size reduction in polar ice

J. Roessiger (1) , P. D. Bons (1) , A. Griera (2) , M. W. Jessell (3) , L. Evans (4) , M. Montagnat (5) , S. Kipfstuhl (6) , S. Faria (7) , I. Weikusat (6)

1 Institut für Geowissenschaften [Tübingen]
2 Departament de Geologia
3 LMTG - Laboratoire des Mécanismes et Transfert en Géologie
4 Australian Crustal Research Centre, School of Geosciences, Monash University
5 EDGe
6 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
7 GZG - Geowissenschaftliches Zentrum Göttingen

Static (or 'normal') grain growth, i.e. grain boundary migration driven solely by grain boundary energy, is considered to be an important process in polar ice. Many ice-core studies report a continual increase in average grain size with depth in the upper hundreds of metres of ice sheets, while at deeper levels grain size appears to reach a steady state as a consequence of a balance between grain growth and grain-size reduction by dynamic recrystallization. The growth factor k in the normal grain growth law is important for any process where grain growth plays a role, and it is normally assumed to be a temperature-dependent material property. Here we show, using numerical simulations with the program Elle, that the factor k also incorporates the effect of the microstructure on grain growth. For example, a change in grain-size distribution from normal to log-normal in a thin section is found to correspond to an increase in k by a factor of 3.5.

Domains: Geomorphology

J. Roessiger, P. D. Bons, A. Griera, M. W. Jessell, L. Evans, et al.. Competition between grain growth and grain-size reduction in polar ice. Journal of Glaciology, 2011, 57 (205), pp.942-948. ⟨10.3189/002214311798043690⟩. ⟨insu-00647437⟩