Science Collected Works - Theses
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ItemNo Preview AvailableThe east Antarctic ice: from ice sheet flow to iceberg dissolution( 1987)This thesis investigates the question of the state of balance, mass budget and dynamics of a large section of the East Antarctic Ice Sheet. The distribution and dissolution of icebergs originating from the icesheet outflux is also determined. Comparison of field measurements collected from oversnow traversing, with balance calculations determined by computer modelling studies, shows that the ice sheet is not likely to be significantly out of balance (i.e. by more than ±10%). By assuming that it is in balance, the ratio of average column velocity to surface velocity is determined to be 0.89. Analysis of the mean strain-rate versus down slope shear-stress indicates values of the commonly used power flow law parameters to be n = 3.2 and k1 = 0.023 bar -n s-1. For the basal ice and high shear zone ice the value of k1 is shown to be k1 = 0.055 bar -n s-1. Comparison of the same results with laboratory work suggests temperatures of the basal ice to be between -5° C and -10° C. The outflux of ice between longitude 90° E and 150° E is estimated to be be 389 km3a-1. Analysis of iceberg size frequency distributions from shipboard observations reveals that Antarctic icebergs (less than 1000m in horizontal dimension) have a median life before breakage, of 0.2 years. This is significantly lower than previously thought. The mean melt rate is estimated to be 0.12 md-1 which agrees broadly with previous laboratory studies for water temperatures averaging + 1°C. More accurate data on iceberg calving, movement and dissolution is required to adequately assess discrepencies from balance computed by ice sheet accumulation and flow studies. Comparison of field measurements collected from oversnow traversing, with balance calculations determined by computer modelling studies, shows that the ice sheet is not likely to be significantly out of balance (i.e. by more than ±10%). By assuming that it is in balance, the ratio of average column velocity to surface velocity is determined to be 0.89. Analysis of the mean strain-rate versus down slope shear-stress indicates values of the commonly used power flow law parameters to be n = 3.2 and k1 = 0.023 bar -n s-1. For the basal ice and high shear zone ice the value of k1 is shown to be k1 = 0.055 bar -n s-1. Comparison of the same results with laboratory work suggests temperatures of the basal ice to be between -5° C and -10° C. The outflux of ice between longitude 90° E and 150° E is estimated to be be 389 km3a-1. Analysis of iceberg size frequency distributions from shipboard observations reveals that Antarctic icebergs (less than 1000m in horizontal dimension) have a median life before breakage, of 0.2 years. This is significantly lower than previously thought. The mean melt rate is estimated to be 0.12 md-1 which agrees broadly with previous laboratory studies for water temperatures averaging + 1°C. More accurate data on iceberg calving, movement and dissolution is required to adequately assess discrepencies from balance computed by ice sheet accumulation and flow studies.
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ItemGlaciological studies made at Wilkes base and on the Antarctic Icecap between Wilkes and Vostok, in 1962( 1964)During 1962 data were collected at Wilkes Base, Antarctica and between Wilkes Base and Vostok, 850 miles inland, on snow accumulation rates and sub-surface ice temperatures. These data have been used in conjunction with information on ice thicknesses to calculate theoretical temperature profiles throughout the icecap, and the validity of these calculations examined by comparison with known temperatures. A method of preparation of plastic replicas of snow crystals and drift snow particles was studied, and the knowledge gained utilised to obtain accurate replicas of drift snow particles inland from Wilkes. Particle size frequency distributions of the drift particles were studied using the plastic replicas for measurement purposes.