1. British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
2. Norwegian Geotechnical Institute, Postboks 3930 Ullevål Stadion, 0806 Oslo, Norway
3. Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK
4. Department of Geology, Centre for Arctic Gas Hydrate, Environment and Climate, UiT – The Arctic University of Norway, N-9037 Tromsø, Norway