1. University of Oslo, UiO, P.O. Box 1072, Blindern, N-0316 Oslo, Norway;
2. The University Centre in Svalbard, UNIS, P.O. Box 156, N-9171 Longyearbyen, Norway;
3. Center for International Climate and Environmental Research - Oslo, Cicero, P.O. Box 1129, Blindern, N-0318 Oslo, Norway;
4. Norwegian Polar Institute, NPI, Polar Environmental Centre, N-9296 Tromsø, Norway;
5. Stockholm University, SE-106 91 Stockholm, Sweden