Topography of streaklines on an Antarctic ice shelf from photoclinometry applied to a single Advanced Land Imager (ALI) image

We investigate the usefulness of the experimental Advanced Land Imager instrument onboard the Earth Observing 1 satellite and a shape-from-shading technique to study streaklines (flow stripes) on the Amery Ice Shelf, Antarctica. Local variations in brightness in the image are directly related to surface topography because the snow surface reflectivity is mostly uniform. Image brightness values are combined with Sun position and streakline orientation to calculate surface topography to centimeter-level vertical precision. The amplitude of the streaklines is typically 1-2 m, and spacing is on the order of 1 km. The streaklines show complex along-flow changes in cross-sectional shape that we interpret to be effects from temporal changes in grounding line dynamics and decay of ice topography due to flow. Cross-sectional areas of the streaklines are calculated at various points along flow to investigate morphological evolution. The study area subscene covers a 28 km /spl times/ 90 km area and covers /spl sim/350 years of ice flow..