Soraya Kaiser^1,2, Guido Grosse^1,3, Julia Boike^1,2 and Moritz Langer^1,2, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Permafrost Research, Potsdam, Germany, (2)Humboldt University of Berlin, Department of Geography, Berlin, Germany, (3)University of Potsdam, Institute of Geosciences, Potsdam, Germany