| Meserve Glacier, Antarctica, was used as a natural laboratory for research on the effective viscosity of subfreezing polycrystalline ice, and on the interaction of cold-based glaciers with their beds. A tunnel was excavated through basal layers of this glacier, which allowed sampling of ice for subsequent measurements of physical and chemical properties and allowed in-situ measurements of ice deformation and glacier sliding.; Analyses of deformation reveal a direct dependence of strain rate on crystal size, which reflects an important role for grain-size-sensitive deformation mechanisms such as grain boundary sliding. The sensitivity of strain rate to chemical impurity content and rock particle content is found to be very low. Variations of crystal size probably are an important control on shear enhancement in the ice sheets. The enhanced shear strain rate inferred from tilt of the Dye 3 borehole can be explained as a result of combined fabric and crystal size variations.; I infer that interactions between Meserve glacier and its bed are influenced by the presence of liquid water films at ice-rock interfaces despite the low temperature of -17°C. Such films allow slip at ice-rock interfaces and cause in-situ segregation of ice into clean lenses amidst dirty layers. Using slip rate and bed surface roughness measurements I infer la liquid film thickness of at least tens of nanometers. Such films should generally be present in polar glaciers, and will have a thickness controlled by soluble impurities and temperature. Analyses of gas and isotopic composition of basal ices reveal that entrainment of bed material into this glacier actively occurs without bulk freeze-on and conventional regelation. Cold-based glaciers have the capacity to striate and erode their beds, and to create glacial landforms.; I reinterpret the clear and persistent relationship between d18O and dD of polar precipitation, which allows isotopic composition to be an important tool for studying glacier-bed interactions and deuterium excess measurements on ice cores to reveal subtropical paleoclimate. I argue that the isotopic composition of precipitation is determined by water-vapor equilibrium to temperatures as low as -35°C. This implies deuterium excess is not sensitive to cloud supersaturation. |
