1. Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
2. College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.
3. School of Environmental Studies, University of Ulster, Coleraine, Northern Ireland BT52 1SA, UK.
4. School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, British Columbia V8W 3P6, Canada.