Estimation of volume changes of mountain glaciers from ICESat data: an example from the Aletsch Glacier, Swiss Alps

Abstract. Worldwide estimation of recent changes in glacier volume is challenging, but becomes more feasible with the help of present and future remote sensing missions. NASA's Ice Cloud and Elevation Satellite (ICESat) mission provides accurate elevation estimates derived from the two way travel time of the emitted laser pulse. In this study two different methods were employed for derivation of surface elevation changes from ICESat records on example of the Aletsch Glacier. A statistical approach relies on elevation differences of ICESat points to a reference DEM while an analytical approach compares spatially similar ICESat tracks. Using the statistical approach, in the upper and lower parts of the ablation area, the surface lowering was found to be from −2.1 ± 0.15 m yr⁻¹ to −2.6 ± 0.10 m yr⁻¹ and from −3.3 ± 0.36 m yr⁻¹ to −5.3 ± 0.39 m yr⁻¹, respectively, depending on the DEM used. Employing the analytical method, the surface lowering in the upper part of the ablation area was estimated as −2.5 ± 1.3 m yr⁻¹ between 2006 and 2009. In the accumulation area both methods revealed no significant trend. The trend in surface lowering derived by the statistical method allows an estimation of the mean mass balance in the period 2003–2009 assuming constant ice density and a linear change of glacier surface lowering with altitude in the ablation area. The resulting mass balance was validated by a comparison to another geodetic approach based on the subtraction of two DEMs for the years 2000 and 2009. We conclude that ICESat data is a valid source of information on surface elevation changes and on mass balance of mountain glaciers.