1. Byrd Polar Research Center,
2. Department of Geological Sciences,
3. Department of Geography, The Ohio State University, Columbus, OH 43210, USA.
4. Institute of Geography, Moscow, Russia.
5. Department of Geosciences, University of Massachusetts, Amherst, MA 01003–9297, USA.
6. Swiss Federal Institute for Environmental Science and Technology (EAWAG) Duebendorf, Switzerland.