Graduate School of Environmental Science, Hokkaido University, N10W8, Sapporo, 060-0810 Japan ; Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320 United States
Graduate School of Environmental Science, Hokkaido University, N10W8, Sapporo, 060-0810 Japan
Institute of Low Temperature Science, Hokkaido University, N19W8, Sapporo, 060-0819 Japan
Institute of Low Temperature Science, Hokkaido University, N19W8, Sapporo, 060-0819 Japan
Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320 United States
Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775-7320 United States