1. Department of Geography, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
2. Environmental Studies, Freshwater Fisheries Laboratory, Pitlochry, Perthshire PH16 5LB, Scotland, U.K.
3. Geological Survey of Denmark and Greenland (GEUS), Department of Environmental History and Climate Change, Thoravej 8, DK-2400 Copenhagen NV, Denmark.
4. ENSIS—ECRC, University College London, 26 Bedford Way, London WC1H 0AP, U.K.