1. Scott Polar Research Institute, University of Cambridge, Cambridge, CB2 1ER, UK
2. Department of Anthropology, Stanford University, Stanford, CA 94305, USA
3. School of Archaeology and Ancient History, University of Leicester, Leicester LE1 7RH, UK
4. Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA
5. Climate Change Institute and School of Biology and Ecology, University of Maine, Orono, ME 04469, USA
6. Department of Earth and Environment, Franklin and Marshall College, Post Office Box 3003, Lancaster, PA 17604, USA
7. Department of Geological Sciences, California State University, Long Beach, California 90840, USA
8. Florence Bascom Geoscience Center, U.S. Geological Survey, Reston, Virginia 20192, USA
9. Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, Wales, SY23 3FL, UK
10. Department of Geography, University College London, Gower Street, London, WC1E 6BT, UK
11. Natural History Museum of Denmark, University of Copenhagen, Gothersgade 130, 1123 København K, Denmark
12. Department of Geography and Environmental Systems, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA