Quantitative Estimates of the Mass Flux and Ice Movement Along the Ice Edges in the Eastern and Southern Weddell Sea

Abstract

Data on the positions of ice edges in the eastern and southern Weddell Sea for the years 1980 to 1984 are presented. These data allow determination of apparent ice movements for the period under consideration, i.e. apparent advance rates and azimuths of ice-edge alteration during particular time intervals. The near-ice-edge movements thus determined are in good agreement with the ice movement as derived from interpretation of Landsat images and West Antarctic ice-stream flow patterns. The apparent areal growth of individual ice shelves in the Weddell Sea region can also be assessed. Together with estimates of near-ice-edge ice thicknesses, an apparent annual discharge rate can be computed. Our results for the Filchner-Ronne and the Brunt ice shelves amount to apparent calving rates of 60x1012, 91x1012 and 24x1012 kg/yr, respectively, which in the case of the Filchner-Ronne Ice Shelf is lower than previous estimates. Most of the major ice shelves in the Weddell Sea region show steadily advancing ice fronts during the period of observation. This has the consequence that the source region for icebergs during this time should be limited mainly to ice fronts in the eastern Weddell Sea. The present results support earlier contentions that large ice shelves undergo episodic, major calving events with frequencies well in excess of a few years, while smaller ice shelves are subject to more frequent calving, thus keeping the ice fronts close to equilibrium.