Aerophotographic interpretation of surface features and an estimation of ice discharge at the outlet of the Shirase drainage basin, Antarctica

Abstract

Aerophotographs taken by the Japanese Antarctic Research Expedition in 1962,1969,1975 and 1977 are analyzed to classify distinctive surface structures, katabatic wind regime at the terminus of the Shirase Glacier (70°S, 39°E), and ice discharge from the Shirase drainage basin is calculated as the sum of ice discharge from three subdivisional drainages with different flow velocities and ice thickness at their outlets. From the displacement of icebergs, the flow velocities of about 2500m・a^ and about 360m・a^ are obtained for the Shirase Glacier and the sheet flow in the west of the Shirase Glacier, respectively. Thicknesses of the icebergs near calving front are also obtained by the aerophotogrammetry. The total discharge from the Shirase drainage basin, 13.4 to 14.7×10^9t・a^, is reported to be more accurate than the values by other authors. Substracting the total discharge from the income previously reported by the other authors, the mass budget of the ice sheet in the basin is estimated to be -0.7 to -2.0×10^9t・a^ during the last several years.