1. Department of Geography Durham University Durham DH1 3LE UK
2. Department of Geosciences University of Rhode Island Kingston Rhode Island 02881 USA
3. U.S. Geological Survey Pacific Coastal Marine Science Center Santa Cruz California 95060 USA
4. Department of Geology Cal Poly Humboldt 1 Harpst Street Arcata 95521 USA
5. U.S. Geological Survey Alaska Science Center Anchorage Alaska 99508 USA
6. Department of Mathematics and Statistics Maynooth University Kildare Ireland