Glaciological Studies on the Ross Ice Shelf, Antarctica, 1973-1978

Abstract

The Ross Ice Shelf Geophysical and Glaciological Survey (RIGGS) yielded measurements of ice velocities, strain rates, accumulation rates, and 1O-m temperatures, which are presented in this paper. Near the grounding line between the ice shelf and the West Antarctic ice sheet, ice velocity ranges from a few meters per year to several hundred meters per year in ice streams. Ice velocity increases as the ice moves seaward, reaching more than 1 km yr-1 in the central portions of the ice front. Ice velocity at Little America V is double earlier estimates. An apparent increase in velocity along parts of the ice front between 1965 and 1975 may simply represent errors in the different estimates. Most of the drainage from West Antarctica into the Ross Ice Shelf flows down two major ice streams, each of which discharges more than 20 km3 of ice each year. Another of the West Antarctic ice streams, previously thought to be very active, is almost stagnant, with drainage rates that are less than half the total snow accumulation within its catchment area, which presumably is growing thicker. Measurement of strain rates is described in detail, and the significance of the various components of the strain rate and rotation rate tensors is discussed. The rate at which the ice shelf thins by creep increases towards the ice front, where the magnitude of vertical strain rates is determined by ice thickness. Intense convergence makes the vertical strain rate positive where major glaciers from the Transantarctic Mountains enter the ice shelf. In contrast, areas of sluggish ice dragged forward by neighboring fast ice streams, undergo rapid longitudinal extension and creep thinning. Accumulation rates from stake measurements support results from analysis of ice cores: values are lower than expected over much of the ice shelf. In a large part of the ice shelf near the West Antarctic ice sheet, 10-m temperatures are about 1°C higher than values that were obtained during the International Geophysical Year (1957–1958). Although this paper does not contain a detailed analysis of the results, there is a brief review of how they can be used to investigate various aspects of ice shelf dynamics.