1. Department of Earth and Planetary Science; University of California; Santa Cruz California USA
2. School of Geography and Environmental Studies; University of Tasmania; Hobart Tasmania Australia
3. School of Civil Engineering and Geosciences; University of Newcastle; Newcastle upon Tyne UK
4. Scott Polar Research Institute; University of Cambridge; Cambridge UK
5. Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography; University of California, San Diego; La Jolla California USA