CHANGE DETECTION ON ALASKA NORTH SLOPE USING REPEAT-PASS ERS-1 SAR IMAGES

Measurements of the C-band (wavelength = 5 cm) radar cross section of an area in the Brooks Range foothills on the North Slope of Alaska usi ng images from the ER-S-1 satellite show significant temporal changes. These changes are strongly correlated with elevation and hillslope or ientation and are greatest on some of the elevated areas and weaker in river drainages. By constructing ''difference images'' using various image pairs, and by analyzing climatological and hydrological data fro m the site, we conclude that the radar backscatter changes are largely due to changes in soil and vegetation liquid water content induced by freeze/thaw events. The correlation with topography in the difference images arises from the dependence of vegetation, organic layer thickn ess, and volumetric water content on hillslope position and orientatio n. These results demonstrate the viability of radar backscatter intens ity comparisons using repeat-pass images as a means of change detectio n.