1. Alfred Wegener Institute for Polar and Marine Research, Box 12 01 61, D-27515 Bremerhaven, Germany;
2. Institute of Marine Research, University of Hamburg, Troplowitzstr. 7, D-22529 Hamburg, Germany;
3. Bjerknes Center, Geophysical Institute, University of Bergen, Allégaten 70, N-5007 Bergen, Norway;
4. Norwegian Polar Institute, Polar Environmental Centre, N-9296 Tromsø, Norway.