[1] Beijing Normal Univ, Coll Global Change & Earth Syst Sci, Beijing 100875, Peoples R China
[2] Univ Lapland, Arctic Ctr, FIN-96100 Rovaniemi, Finland
[3] Natl Oceanog Ctr, Liverpool L3 5DA, Merseyside, England
[4] Univ Copenhagen, Niels Bohr Inst, Ctr Ice & Climate, DK-2100 Copenhagen, Denmark