1. Division of Earth‐System Sciences Korea Polar Research Institute 26 Songdomirae‐ro Yeonsu‐gu Incheon 21990 South Korea
2. Kochi Institute for Core Sample Research JAMSTEC B200 Monobe Nankoku Kochi 783‐8502 Japan
3. Center for Computational Astrophysics National Astronomical Observatory of Japan 2‐21‐1 Osawa Mitaka Tokyo 181‐8588 Japan