1. Leibniz Institute for Applied Geophysics, Stilleweg 2, 30655 Hannover, Germany
2. Institute of Geophysics and Meteorology, University of Cologne, Albertus-Magnus-Platz, D-50923 Cologne, Germany
3. GEOMAR Helmholtz Centre for Ocean Research, Wischhofstraße 1-3, 24148 Kiel, Germany
4. TU Bergakademie Freiberg, Institute of Geophysics and Geoinformatics, Gustav-Zeuner-Straße 12, 09599 Freiberg, Germany