1. College of Life and Environmental Sciences, University of Exeter, Exeter, UK
2. School of Physics and Astronomy, University of St Andrews, St Andrews, UK
3. School of Geosciences, University of Edinburgh, Edinburgh, UK
4. Scott Polar Research Institute, University of Cambridge, Cambridge, UK
5. Jackson School of Geosciences, University of Texas Institute for Geophysics, University of Texas at Austin, Austin, GE, USA