Ice sheet motion and topography from radar interferometry

Both topography and motion information are present in repeat pass ERS-1 interferograms over ice sheets, We demonstrate that the topography is separable from the surface displacement field when a sequence of radar images are available, If the velocity field is constant over the time span of observation, the topography can be derived from differential interferograms formed from sequential observations, With this measurement, a pure displacement field can then be obtained by removal of the topographic contribution to the interferometric phase at each pixel, Further, we discuss how the vertical and horizontal components of displacement affect the interferometrically-derived motion field, We illustrate our approach with four successive (3-day repeat) ERS-1 images of a flow feature in northeastern Greenland.