| Summary: | As a new means of monitoring the flow velocities and grounding-line positions of ice streams, which are indicators of response of the Antarctic and Greenland ice sheets to climatic change or internal instability, the method of satellite radar interferometry (SRI) is here proposed and applied to the Rutford Ice Stream, Antarctica. The method uses phase comparison of the radar signal obtained for a pair of SAR images taken a few days apart to plot an interferogram which directly displays relative ground motions that have occurred in the time interval between images. The detection limit is about 1.5 mm for vertical motions and about 4 mm for horizontal motions in the radar beam direction. In the Rutford Ice Stream, SRI velocities agree fairly well with earlier ground-truth data over a longitudinal interval of 29 km; the comparison suggests a secular decrease in velocity of about 2 percent from 1978-80 to 1992.
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