1. National Research Council Canada, Montreal H4P 2R2, Quebec, Canada
2. Greenland Climate Research Centre, Greenland Institute of Natural Resources, Nuuk 3900, Greenland
3. Department of Estuarine and Delta Systems, Royal Netherlands Institute of Sea Research, Utrecht University, Yerseke 4401 NT, The Netherlands
4. Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Copenhagen 1871, Denmark