Local Rates of Ice-Sheet Thickness Change in Greenland

The rate of ice-sheet thickness change is calculated for 10 sites in Greenland by comparing measured values of ice vertical velocity and snow-accumulation rate. Vertical velocities are derived from repeat surveys of markers using precision global positioning system techniques, and accumulation rates are determined from stratigraphic analysis of firn cores. The results apply to time-scales covered by the firn-core records, which in most cases are a few decades. A spectrum of thickness-change rates is obtained, ranging from substantial thinning to slow thickening. The sites where ice-sheet thinning is indicated are located near the ice-sheet margin or in outlet glacier catchments. Interior and high-elevation sites are predominantly in balance or thickening slowly. Uncertainties in the rates of thickness change are dominated by errors in the determination of accumulation rates. The results of this work are broadly comparable with regional estimates of mass balance obtained from the analysis of catchment input vs discharge

Devon Island Programs, 1968

Four field parties, studying glaciology, botany and ornithology, used the Arctic Institute's facilities on Devon Island during the summer of 1968. The botanical and ornithological studies were carried out from the Base Camp near Cape Sparbo, while the glaciological work was pursued from field camps on the ice cap and the Sverdrup Glacier. ..

Thickness Changes on Whillans Ice Stream and Ice Stream C, West Antarctica, Derived from Laser Altimeter Measurements

Repeat airborne laser altimeter measurements are used to derive surface elevation changes on parts of Whillans Ice Stream and Ice Stream C, West Antarctica. Elevation changes are converted to estimates of ice equivalent thickness change using local accumulation rates, surface snow densities and vertical bedrock motions. The surveyed portions of two major tributaries of Whillans Ice Stream are found to be thinning almost uniformly at an average rate of similar to 1 m a(-1). Ice Stream C has a complicated elevation-change pattern, but is generally thickening. These results are used to estimate the contribution of each surveyed region to the current rate of global sea-level rise

The Surface Mass-Balance of Marie Byrd Land, Antarctica: Data Interpretation and Application

The University Archives has determined that this item is of continuing value to OSU's history.A method is described to determine accurate and precise mass balance from bamboo poles at the surface of the ice sheet upstream from Byrd Station, Antarctica. The method includes corrections for snow and firn settling and for the migration of anchoring position along the pole. Methods for determining snow and firn densities from pits using sawed blocks (after Schytt 1958) are described. Although our sawed block data contain a systematic error, this technique provides much more precise densities than the snow sampler technique. We recommend an improved sawed block technique for future work. The surface mass-balance is largest near the ice crest and shows variations that are related to surface slope. The pattern is probably related to orographic precipitation from air masses originating in the Amundsen Sea and to katabatic winds. The importance of spatial surface mass-balance to deep core interpretation is discussed.National Science Foundation Grant GV-26137X3Office of Polar Programs Grant OPP 74-02716-A0

Analysis of the Byrd Station Strain Net, Antarctica

On cover: RF 2500.This report presents some results of field investigations relating to the study of glacier flow in Marie Byrd Land, Antarctica. The physical quantities necessary for a solution to the problem of the mode of flow of the continental ice sheet in the Ross glacial drainage basin are being sought by several principal lines of investigation: determination of surface strain rate and surface slope by analysis of precise surveys of the Byrd Station Strain Net that have been carried out by the Topographic Branch of the U.S. Geological Survey; determination of strain rate and temperature distribution at depth in the deep hole at Byrd Station drilled by the U.S. Army Cold Regions Research and Engineering Laboratory; determination of ice thickness and of glacier bed configuration and conditions by geophysical exploration, including seismic, gravimetric, magnetic and radio-echo sounding methods; analysis of the structure and dynamic physical properties of ice; and observation of snow deposition and metamorphosis and surface morphology in order to explain parts of the core from Byrd Station deep drill hole, and estimate the mass balance. Much of the material presented in the report is based upon observations made by field parties which were based at Byrd Station and operated in the region of the Byrd Station Strain Net, which lies between Byrd Station and the Ross-Amundsen ice divide, during the austral summers of 1967-68, 1969-70, 1971-72, and 1973-74.National Science Foundation Grants GA-1141, GA-14425 and GV-26137X