Flow of Antarctic ice under high hydrostatic pressures

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Main results obtained in this project are summarized as follows.1. Plastic deformation of Antarctic ice at temperatures near melting point and under high hydrostatic presures (1). The dependence of strain rate on stress was not effected by temperature and hydrostatic pressure. (2). Hydrostatic pressure caused the softening of ice crystals. (3). The strain rate at temperatures near melting point increased compared with that extraporated from low temperature region.2. Behavior of lattice defects which influence the deformation of ice (1). The process of deformation of ice cryatals was determined by selfinterstitials which were interstitial water molecules and influenced climb motion of dislocations in ice. (2). X-ray analysis of deformed ice crystals under high hydrostatic pressures indicated that the pressure dependence of diffusion coefficient of ice was the same as that of the deformation rate.3. Air-hydrate single crystals in ice Air-hydrate crystals of which the size was about 10 - 100 m existed in ice sheet deeper than 1000m. The crystal is considered to affect the flow of ice sheets. (1). Air-hydrate crystal could be nucleated artificially in a tank made for a special high hydrostatic pressure experiments. The number of nucleated crystals depended on total air content in ice and the nucleation rate depended on temperature. (2). X-ray analysis of Air-hydrate crystals revealed that the structure of air-hydrate crystals was belong to " structure II " of hydrate crystals and determined the position of O_2 and N_2 molecules in cages of hydrate.