This image shows the movement of the Lambert Glacier. The ice velocity vectors were obtained by using RADARSAT Synthetic Aperture Radar (SAR) imagery from the 2000 Antarctic Mapping Mission. Yellow represents the areas of no motion, which are either exposed land or stationary ice. The smaller confluent glaciers have generally low velocities, shown in green, of 100-300 meters (330-980 feet) per year, which gradually increase as they flow down the rapidly changing continental slope into the upper reaches of the faster flowing Lambert Glacier.
Most of the Lambert Glacier itself has velocities between 400-800 meters (1,310-2,620 feet) per year, with a slight slowing in the middle section. As the glacier extends across Amery Ice Shelf, velocities increase to 1000-1200 meters (3,280-3,937 feet) per year as the ice sheet spreads out and thins. Only a handful of in-situ velocity measurements have been previously reported of this huge glacier system. While the in-situ and radar-derived measurements appear to be qualitatively similar, the extent and accuracy of the new measurements are unprecedented and provide quantitative baselines for future comparisons. The ice velocities are obtained from pairs of images obtained 24 days apart, using a technique called radar interferometry. This technique enables a highly precise alignment of image pairs that provides accurate measurements of topography as well as surfaces that have changed or moved over the short time interval, including glaciers.
The Antarctic Mapping Mission is a joint project between NASA and the Canadian Space Agency. The project is led by Ohio State University in Columbus in partnership with the Alaska Synthetic Aperture Radar (SAR) Facility at the University of Alaska Fairbanks, NASA's Jet Propulsion Laboratory, Pasadena, Calif., and the Vexcel Corporation, Boulder, Colo. The Canadian Space Agency's RADARSAT-1 satellite carries a synthetic aperture radar, an imaging radar sensor that operates at C-band (5.3 GHz frequency) with horizontal transmit-horizontal receive polarization from an orbital altitude of about 800 kilometers (500 miles). The 1997 Antarctic Mapping Mission took place between Sept. 19 and Oct. 14 and mapped the entire Antarctic continent. The 2000 Antarctic Mapping Mission lasted from Sept. 3 to Nov. 4 and obtained complete coverage of Antarctica north of 82 degrees south latitude.
More information on the mission is available on the Internet at http://www-bprc.mps.ohio-state.edu/radarsat. Images associated with this release are available at http://www.jpl.nasa.gov/pictures/antarctica/ .
Information about the first Antarctic Mapping mission is available from this Candian Space Agency web site.
Image courtesy Canadian Space Agency/NASA/Ohio State University, Jet Propulsion Laboratory, Alaska SAR facility