Isotropic and Anisotropic Flow Relations for Ice Dynamics

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Abstract
A flow relation for the minimum strain-rates for isotropic ice is presented. This flow relation has been compiled from laboratory tests in shear and compression, and covers the temperature and stress ranges typical of natural ice masses. However, the ice in natural ice masses is mostly anistropic. Three cores drilled at Law Dome, Antarctica, are used as examples to illustrate some of the different anisotropies that develop in ice masses in relation to the stress configurations and accumulated strains. For the shear- or compression-stress configurations, anistropic flow rates can be derived as enhancements of the minimum isotropic flow rates for the particular stress, temperature, and stress configuration. For compression, this enhancement asymptotically approaches 3. For shear, the enhancement may be as high as 8. For combinations of shear and compression, further tests are required.