Geodetic Results of the Ross Ice Shelf Survey Expeditions, 1962–63 and 1965–66

Abstract

By means of modern geodetic observation techniques the ice movement along an east-west and a north-south profile across the Ross Ice Shelf, Antarctica, was measured during the two Antarctic summers, 1962–63 and 1965–66. 103 markers were placed on the 910 km long traverse. Distances were measured by tellurometer, and traverse angles by a precision theodolite between all consecutive markers, normally 8 to 9 km apart. For this type of observation method, six men distributed into three groups of two men each were necessary.The main part of the paper deals with data processing and with the computation of the ice movement. As the ice moves, the geometrical configuration of the traverse changes during the epoch of observation. For this “reduction to epoch” problem two methods are described in detail: (1) time reduction of observations, and (2) time reduction of positions. Between the two field journeys, only linear ice movement can be assumed. It is possible, however, to determine acceleration and curvature of the ice flow at all traverse points where the traverse angles differ considerably from 180°.The result of all computations is the field of velocity vectors along the traverse. Obvious characteristics are the rapid increase of velocity between the McMurdo Ice Shelf and Ross Ice Shelf, the uniform and nearly parallel movement in the middle of the ice shelf (maximum velocity 935 m year−1), the decrease of velocity along the north-south profile, and the systematic increase of divergence of the flow lines towards the ice margins. Careful study of the velocity vector field shows some deviations from an entirely uniform distribution.

The Recent Advance of the Ross Ice Shelf Antarctica

“…This advance was consistent with reports, estimates, and measurements of generally northward flow along the northern edge of the ice shelf (e.g. David, 1914;Mecking, 1928;Dorrer and others, 1969;Robin, 1975;Thomas and others, 1985). In addition, it is generally appreciated that "some segments of an ice shelf may yield icebergs at a more or less constant rate over a period of a few years, while other parts of the same shelf may experience only a single breakout in a decade or longer" (Swithinbank and Zumberge, 1965).…”

Investigation of Bottom Mass-Balance Rates by Electrical Resistivity Soundings on the Ross Ice Shelf, Antarctica

“…Unfortunately, the profiles at Q-13, closest to (about 90 km from) the ice front, are disturbed by local inhomogeneities, nevertheless, the best model fitted to the data, as well as the temperature measurements to a depth of 100 m, suggests no bottom melting. With an ice movement-rate here of the order of I km year-I (Dorrer and others, 1969), that would mean no measurable average melting over a few hundred kilometers up-stream from Q-I3. This is consistent with the estimate of Zumberge (1964), based on strain measurements, that the melt-rate decreases from about I m year-I near the ice front to zero at a distance of 80 km from the margin.…”

Ice-thickness Patterns and the Dynamics of the Ross Ice Shelf, Antarctica

“…Lennox-King Glacier also produces a continuous strong reflector. The direction of the flow lines has been interpreted not only from the zonation in the ice but also from actual measurements (Swithinbank, 1963;Dorrer and others, 1969;Thomas, 1976; personal communication from G . de Q .…”

“…To the west such correlation has not yet proven possible owing to the absence of clearly defined bands in the ice flowing from West Antarctica. The few flow lines shown in Figure 3, west of 0° grid longitude, are based on actual measurements of ice movement (Dorrer and others, 1969;Thomas, 1976) and the correlation ofa few specific features (e.g. the "steps" discussed below).…”