1. School of Geographic Science Nantong University Nantong 226007 China
2. Alfred Wegener Institute Helmholtz Center for Polar and Marine Research Research Unit Potsdam Potsdam 14473 Germany
3. Kazan Federal University Kazan 420018 Russia
4. Institute of Geology and Mineralogy University of Cologne Cologne 50674 Germany
5. Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China
6. University of the Chinese Academy of Sciences Beijing 100049 China