1. Department of Geodesy and Geoinformation, Research group Remote Sensing, Vienna University of Technology, Vienna 1040, Austria
2. Austrian Polar Research Institute, c/o Universität Wien, 1090 Vienna, Austria
3. Section Climate Change Impacts, ZAMG- Zentralanstalt für Meteorologie und Geodynamik, Vienna 1190, Austria
4. Hemholtz-Zentrum für Polar und Meeresforschung, Periglacial Research, Alfred Wegener Institute, Potsdam 14473, Germany