| Summary: | Seven Magnavox MX1502 satellite receivers were used during the summers of 1980 and 1981 to obtain the movement of 22 stations at three locations on the ice sheet of interior Greenland. The research program was successful with only minor equipment problems. Severe weather conditions that delayed the servicing of the receivers and operator errors resulted in the loss of only a minor amount of data. Two receivers were located at stationary sites on the west coast of Greenland for the whole of both seasons. This allowed the short arc method to be used to obtain relative coordinates with higher precisions than are obtainable by point positioning. The stations on the ice sheet were located at an approximate latitude of 65 degrees North and crossed the southern dome of Greenland. The positions of the stations on the ice sheet were obtained with formal accuracies of better than 0.20 meters. However, the actual accuracies obtained were not this precise, particularly in the elevations. The station coordinates were obtained from the satellite data. From the coordinates, the station velocities, as well as ice sheet slopes, and the baseline lengths between the stations were calculated. Changes in the baseline lengths between 1980 and 1981 were used to calculate strain rates. The two stations that are nearest to the ice crest are not moving in the expected direction (northeast) but instead are moving in a direction slightly west of north. This indicates that the positions of the ice crest and the ice divide do not coincide. The other stations west of the ice divide are moving 50 to 75 degrees west of north. The stations east of the ice divide are moving 50 to 70 degrees east of north. The stations farther from the ice divide are moving more nearly east or west. The angle between the direction of maximum extension and the direction of motion is generally small with the direction of maximum extension more nearly east-west. Thus, there is no major surface shearing in the motion of the ice on either side of the ice divide. In two of the three areas studied, the minimum strain is compressive. The magnitude of the maximum strain and the velocities increase away from the ice divide and with increasing slope. NSF Grant DPP-8008356A01 NASA Research Grant NSG5265
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