[A-CC29] Ice cores and paleoenvironmental modeling

[ACC29-12] Microscopic analysis of insoluble particles in an ice core drilled on Trambau Glacier in Nepali Himalayas

*Fuki Konishi¹, Nozomu Takeuchi¹, Akane Tsushima¹, Nao Esashi², Ryu Uemura³, Sumito Matoba⁴, Iizuka Yoshinori⁵, Koji Fujita² (1.Chiba University, 2.Graduate School of Environmental Studies, Nagoya University, 3.Nagoya University, 4.Pan-Okhotsk Research Center, Institute of Low Temperature Science, Hokkaido University , 5. Institute of Low Temperature Science, Hokkaido University )

Insoluble particles in ice cores are used as proxies of the past environment and as indicators of annual layer boundary. Microscopic analyses of insoluble particles in an ice core from a Himalayan glacier were conducted. The ice core was drilled in 2019 at an altitude of 5860 m of a snowfield of Trambau Glacier in the Nepali Himalayas. The ice core was drilled from the surface the glacier down to 81 m in depth. In this study, the samples of 4-10 m in depth were analyzed. Microscopy revealed that the ice core contained various insoluble particles including pollens, mineral particles, algal cells and fungal spores. Pollen grains were morphologically identified into six taxa of plants: Pinus, Abies, Tsuga, Betula, Alnus, and Artemisa. The concentrations of pollen grains showed 12 distinct peaks in the depth range analyzed and they are most likely to represent spring layers. However, these peaks further contained various pollens types including those released in spring and autumn. The mixture of spring and autumn pollens suggests that the summer layers completely melted and run out. The concentration of mineral particles also showed several peaks, which coincided with those of the spring pollen. This is consistent with an increase of airborne dust from winter to spring. Snow algae were found in only three layers, but their concentration was much higher than pollen grains, suggesting that they grew in situ on the glacier in a certain conditions of melting season. As algal growth requires the certain length of growth period, the presence of algae may be indicative of intense summer melting or hiatus of annual layers. These results indicate that the total pollen concentration dispersed in spring is useful to determine the annual layer in this ice core.