Investigations of the glacier surface properties and ice velocity of the south Patagonian icefield from synthetic aperture radar (SAR)

Shuttle imaging radar C/X band synthetic aperture radar (SIR-C/X-SAR) views of the South Patagonian Icefield in southern Chile and Argentina demonstrate the ability of spaceborne multiparameter radar to detect climatically driven changes in the snow and ice conditions on glaciers, observe the effects of weather on the glacier surface, and measure the ice velocity. The SIR-C/X-SAR system aboard space shuttle Endeavor acquired images during two 11-day missions in April and October 1994. The radar signatures of differing snow and ice conditions are distinctive and homogeneous over large areas of the ice fields and are interpreted by correlating the radar characteristics with elevation of the snow and ice surfaces and with changes in the meteorological conditions. We are able to define four "radar glacier zones": The spatial changes in the radar glacier zones between April and October are consistent with colder temperatures recorded in October, producing drier snow conditions at lower elevations than in April.; SIR-C/X-SAR imaged a portion of the SPI for five successive days during both the April and October missions. A significant meteorological event occurred during each mission, including a major storm in April and a sharp temperature decrease in October. Ground station and satellite meteorological, and hydrological data are combined with the daily X-SAR images to interpret changes in glacier surface conditions caused by meteorological events. The changes in the radar-defined glacier zones due to the April precipitation event are subtle while the October temperature drop causes significant backscatter increases. Our results suggest that trends in HPS glacier surface and near surface conditions observable from spaceborne SARs are not significantly masked by precipitation events.; Interferometric synthetic aperture radar (InSAR) data of a portion of the Hielo Patagonico Sur (HPS), Chile were collected over a four day span in October 1994 and used to generate an ice velocity map. The three outlet glaciers in the radar scene act as ice streams within the icefield flanked by slower moving ice. A flow divide between two of the glaciers is mapped by locating a narrow band of near-zero ice velocity. Horizontal ice surface velocity profiles calculated along flowlines show there is a high degree of spatial variability in velocity along the center-lines with velocities reaching over 2.5 m/day. Longitudinal strain rates, calculated from these velocities, at the locations of the initiation of crevassing agree with theoretical values computed for ice fracture under longitudinal tension.