This thesis uses ground-based, airborne and spaceborne elevation measurements to estimate elevation change and mass balance of glaciers and ice caps on the Svalbard archipelago in the Norwegian Arctic. Remote sensing data are validated against field measurements from annual campaigns at the Austfonna ice cap. A new and more accurate DEM of the ice cap is constucted by combining SAR interferometry with ICESat laser altimetry. The precision of the DEM is sufficient to correct ICESat near repeat-tracks for the cross-track topography such that multitemporal elevation profiles can be compared along each reference track. The calculated elevation changes agree well with more accurate elevation change data from airborne laser scanning and GNSS surface profiling. The average mass balance of Austfonna between 2002 and 2008 is estimated to -1.3 ± 0.5 Gt y-1, corresponding to an area-averaged water equivalent elevation change of -0.16 ± 0.06 m w.e. y-1. The entire net loss is due to a retreat of the tidewater fronts. Earlier time periods are difficult to assess due to limitations in the amount and quality of previous elevation data sets. Other Svalbard regions have been precisely mapped by aerial photogrammetry, so the ICESat profiles from 2003-2008 can be compared with existing topographic maps and DEMs from 1965-1990. The mass balance for this period is estimated to -9.7 ± 0.6 Gt y-1 (or -0.36 ± 0.02 m w.e. y-1), excluding Austfonna. Repeat-track ICESat data are also analysed for the entire Svalbard yielding an average 2003-2008 mass balance of -4.3 ± 1.4 Gt y-1 (or -0.12 ± 0.04 m w.e. y-1) when tidewater front retreat is not accounted for. The most accurate elevation change estimates are obtained using all available ICESat data in a joint regression where surface slope and elevation change are estimated for rectangular planes that are fitted to the data along each track. The good performance of the plane method implies that it can also be used in other Arctic regions where accurate DEMs typically are not available.
List of papers. Paper IV are removed from the thesis due to copyright restrictions.
Paper I Moholdt, G., and Kääb, A.:A new DEM of the Austfonna ice cap by combining differential SAR interferometry with ICESat laser altimetry. Polar Research 2012, 31, 18460 doi:10.3402/polar.v31i0.18460Creative Commons Attribution-Noncommercial 3.0 Unported License
Paper II Moholdt, G., Hagen, J. O., Eiken, T., and Schuler, T. V.: Geometric changes and mass balance of the Austfonna ice cap, Svalbard. The Cryosphere, 4, 21-34, 2010. doi:10.5194/tc-4-21-2010
Paper III Nuth, C., Moholdt, G., Kohler, J., Hagen, J. O. and Kääb A.: Svalbard glacier elevation changes and contribution to sea level rise. Journal of Geophysical Research - Earth Surface, 115, F01008, 16PP, 2010. Copyright (2010) American Geophysical Union doi:10.1029/2008JF001223
Paper IV Moholdt, G., Nuth, C., Hagen, J. O. and Kohler J.: Recent elevation changes of Svalbard glaciers derived from ICESat laser altimetry. Remote Sensing of Environment, 114, 2756-2767, 2010. doi:10.1016/j.rse.2010.06.008