Arctic and Antarctic Research Institute, Bering Street 38, 199397 St. Petersburg, Russia

St. Petersburg State University, Faculty of Geography and Geoecology, 10 line V.O., 33, 199178, St. Petersburg, Russia

Water and Environmental Research Center, Institute of Northern Engineering, 306 Tanana Drive, Duckering Room 437, University of Alaska Fairbanks, Fairbanks, Alaska 99775-5860, USA

Department of Geosciences, University of Massachusetts, P.O. Box 35820, Amherst, MA 01003-5820, USA

St. Petersburg State University, Faculty of Geography and Geoecology, 10 line V.O., 33, 199178, St. Petersburg, Russia

Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg, 14471 Potsdam, Germany

Institute of Applied Geology, Technical University of Berlin, Ackerstrasse 76, Sek ACK 1-1, 13355 Berlin, Germany