A surface and volume scattering retracking algorithm for ice sheet satellite altimetry

An algorithm based on a combined surface and volume scattering model that is used to retrack individual altimeter waveforms from the ice sheets is developed. Because the combined model is nonlinear, an iterative least-squares procedure is used to fit the combined model to the return waveforms. This retracking algorithm can be used to assess the accuracy of elevations produced by current retracking algorithms, which do not account for subsurface volume scattering. This is extremely important if repeated altimeter elevation measurements are to be used to accurately detect changes in the mass balance of the ice sheets. In addition, by analyzing the distribution of the model parameters over large portions of the ice sheet, quantitative estimates of regional and seasonal variations in the near-surface properties of the ice sheets can be obtained