The role of a liquid phase in the deformation behaviour of ice

Knowledge of the mechanical response of ice containing a liquid phase is important for modelling the flow of temperate glaciers. Laboratory experiments demonstrate that a few per cent of melt can have a large effect on ice viscosity (De la Chapelle etal., 1999). The role of the liquid phase is analysed by considering the reduction of the internal stress field induced by the mismatch of slip at grain boundaries. The deformation regime with n < 2 is extended toward high stresses when the water content increases. A much larger effect was observed in debris-laden ice by Echelmeyer & Zhonxiang (1987) and Cohen (2000). The presence of liquid films around particles even at low temperature would be at the origin of a strong decrease of ice viscosity. In this case, this large effect of interfacial water is not directly related to the volume of the liquid phase but rather to the surface area of particles. The liquid phase would contribute to the accommodation of slip by promoting some grain adjustment and preventing the formation of deformation inhomogeneities.

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