Deformation and recrystallization in polar ice sheets were studied via analysis of the structure along 2 deep ice cores. It was shown that the deformation of polar ice at low stresses involved intracrystalline slip, accommodated by grain-boundary migration. A deformation model was developed which was based upon an equilibrium between work-hardening and recovery. The decrease in dislocation density was attributed to grain-boundary migration that was associated with grain growth and to the formation of boundaries by recrystallization. The level of the dislocation density along the ice cores, according to the model, was about 1011/m2. This value agreed with data from the synchrotron X-ray diffraction of samples taken along the core. The deformation model could account for the deformation of polar ice at low stresses. A flow law with a stress exponent smaller than 2 could be related to the efficiency of grain boundary migration during recovery.

Rate Controlling Processes in the Creep of Polar Ice, Influence of Grain Boundary Migration Associated with Recrystallization. M.Montagnat, P.Duval: Earth and Planetary Science Letters, 2000, 183[1-2], 179-86