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Normal grain growth experiments were performed using polycrystalline ice samples with and without air bubbles. The bubble-free polycrystalline ice was prepared by a special sample preparation technique that employed a phase change method. The ice samples with air bubbles were prepared from a mixture of ice powder and pure distilled water using conventional methods. The temperature dependencies of the rate of grain growth were measured in artificial polycrystalline ice samples with and without air bubbles. The average grain growth exponent n of the ice with bubbles was much greater than the theoretical value of 2, while that of bubble-free ice was close to 2. The activation energy for the grain boundary migration of bubble-free ice was 110–120 kJ mol −1 , whereas that of the ice with bubbles was between 40 and 70 kJ mol −1 . The observation of the microscopic images of samples and analyses of the evolution of bubble size distribution and location during grain growth revealed that small air bubbles are caught and swept by moving grain boundaries and a coalescence of bubbles occurs. This indicates that the slow grain boundary migration of ice with bubbles is controlled by the migration of air bubbles dragged by grain boundary migration.

The deformation behavior of the individual grains which constitute polycrystalline ice has been observed in situ during plane strain deformation using thin, columnar-grained specimens. The relationship between the c-axis orientation and the strain of individual grains was examined. It was found that the strain of an individual grain was proportional to the geometric factor for the crystallographic orientation of the grain (the Schmid factor for the slip direction), to the local mean strain surrounding the grain and inversely proportional to the local mean Schmid factor. Moreover, the local mean strain was proportional to the fourth power of the local mean Schmid factor. From these results it is derived that the strain rate for steady state flow of polycrystalline ice is proportional to the fourth power of the mean value of the Schmid factor of each grain in the aggregate.

A new formulation of the flow law of polycrystalline ice was derived for an rbitrary c-axis orientation fabric pattern. The rate factor of the flow law is given by a geometrical factor that can be calculated with c-axis fabric data and stress condition. A theoretical calculation combining this flow law with a lattice rotation model by intracrystalline slip in the constituent grains predicts the development of characteristic fabric patterns observed in many laboratory experiments and in the field. According to this flow model of polycrystalline ice, if significant recrystallization does not occur uniaxial compression makes the ice body harder with increasing strain, whereas simple shear makes the ice body softer with strain. This may significantly affect ice sheet dynamics.