1. Oceanography and Climate Group, Institute of Marine Research, P. O. Box 1870, Nordnes, Bergen, Norway
2. Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, USA
3. Marine Mammal Group, Institute of Marine Research, Tromsø, Norway
4. Ocean Acoustics Group, Alfred-Wegener-Institute, Helmholtz-Center for Polar and Marine Research, Klussmannstrasse 3d, 27570 Bremerhaven, Germany