1. National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK.
2. National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, UK.
3. Departments of Earth Sciences and Geography, Durham University, Durham DH1 3LE, UK.
4. School of Environmental Sciences, University of Hull, Cottingham Road, Hull HU6 7RX, UK.
5. Formerly at Chevron Energy Technology Company, 6001 Bollinger Canyon Road, San Ramon, CA 94583, USA.
6. Department of Geography, Durham University, South Road, Durham DH1 3LE, UK.