Aufeis in the Ivishak River, Alaska, mapped from satellite radar interferometry

Aufeis deposits form every year on many rivers on the North Slope of Alaska; and, through repeated episodes of overflow and freezing, they may reach a thickness of more than 3 m. The presence of aufeis in a drainage basin tends to stabilize river discharge in the same way as a glacier does, by providing melt water during hot dry periods. This distribution of aufeis deposits along the rivers is discontinuous because of variations in channel geometry and under-ice water supply, and monitoring their growth during the winter is generally impractical. However, experiments using satellite radar interferometry (SRI) to map changes in the extent of aufeis near the junction of the Ivishak and the Echooka Rivers in the northern Brooks Range during the winter have produced promising results. Interferograms of the area were made from pairs of images acquired by the European Space Agencyʹs First Earth Remote Sensing Satellite in January through March 1994. The results indicate that aufeis deposits can be mapped on interferograms as areas in river valleys in which the radar phases are poorly correlated and radar backscatter values frequently change. The ability of SRI in monitoring subtle winter aufeis processes fills a major gap in the study of aufeis by remote sensing.