[A-CC26] Ice cores and paleoenvironmental modeling

[ACC26-11] Ice core drilling on a high-elevation accumulation zone of Trambau Glacier in the Nepal Himalaya

*Nao Esashi¹, Akane Tsushima², Ryu Uemura¹, Yoshinori Iizuka³, Sumito Matoba³, Koji Fujita¹ (1.Graduate School of Environmental Studies, Nagoya University, 2.Graduate School of Science, Chiba University, 3.Institute of Low Temperature Science, Hokkaido University)

We drilled an 81.2-m-long ice core in the accumulation area (5,860 m above sea level) of the Trambau Glacier, Rolwaling region, Nepal Himalaya, during October–November 2019. The drilling operation was conducted with a lightweight electro-mechanical drill system after two reconnaissance field expeditions in the post-monsoon seasons of 2017 and 2018, during which two shallow firn cores were drilled with a hand auger. The drill system and ice core samples were transported by helicopter at a high elevation of 6,000 m above sea level. A further challenging issue was the ice core transportation between Nepal and Japan, as no regular commercial flight was available for the frozen samples. The addition of dry ice imported from India immediately prior to leaving Nepal allowed the ice core samples to be successfully transported to a cold room in Japan, and remain in a frozen state. Stratigraphic observations during the drilling operation suggest the drill site has been affected by melting and refreezing. However, preliminary water stable isotope data in the shallow firn core indicate that the ice core preserves climatic signals during the past 150 yr.