[1] Nanjing Univ, Int Inst Earth Syst Sci, Nanjing 210023, Peoples R China
[2] Nanjing Univ, Jiangsu Prov Key Lab Geog Informat Sci & Technol, Nanjing 210023, Peoples R China
[3] Univ Copenhagen, Ctr Permafrost CENPERM, Dept Geosci & Nat Resource Management, Oster Voldgade 10, DK-1350 Copenhagen, Denmark
[4] British Antarctic Survey, Madingley Rd, Cambridge CB3 0ET, England
[5] Univ Copenhagen, Nat Hist Museum Denmark, Oster Farimagsgade 5, DK-1353 Copenhagen, Denmark