[A-CC27] アイスコアと古環境モデリング

[ACC27-07] A 146 year record of atmospheric dust from Trambau Glacier ice core, Nepal Himalaya

*江刺 和音¹、對馬 あかね²、植村 立¹、的場 澄人³、飯塚 芳徳³、足立 光司⁴、木名瀬 健⁵、Kayastha Rijan B.⁶、藤田 耕史¹ (1.名古屋大学大学院環境学研究科、2.千葉大学大学院理学研究院、3.北海道大学低温科学研究所、4.気象庁気象研究所、5.海洋研究開発機構、6.カトマンズ大学)

キーワード：アイスコア、鉱物粒子、ヒマラヤ、山岳氷河

Mineral dust affects climate through direct radiative forcing by scattering and absorbing solar radiation in the atmosphere and by accelerating snow and ice melting through reduced albedo when deposited on snow surfaces. The concentration and composition of dust deposited on glaciers reflect the surface conditions of the source regions and atmospheric conditions during transportation. Dust records in ice cores provide insights into historical atmospheric and land surface environments. However, ice cores drilled in high-altitude Himalayan glaciers are limited. To investigate historical variations in dust concentration in the Himalayas, we conducted ice core drilling at an elevation of 5862m on the Trambau Glacier in the Rolwaling region of the Nepal Himalaya. The ice core, covering 146 years (1874-2019), was dated using seasonal variations in NO₃^- and Ca²⁺. The 81-m ice core was divided into 1637 samples (~5 cm interval), and dust concentration (particle size ranging from 0.6 to 10 µm) was measured using the Coulter Counter Multisizer ^TM3. Dust concentrations in the Trambau ice core shows a maximum concentration in the 1880s over the past 146 years, followed by a long-term increasing trend from 1890 to the present. This trend is consistent with the rate of increase in dust concentrations observed in nearby Himalayan ice cores. Furthermore, the dust concentration displays periodic fluctuations with a 20-30-year cycle, consistent with the Atlantic Multi-decadal Oscillation (AMO). This suggests a connection between the environmental changes (precipitation, temperature, and land surface conditions) in the dust source regions and AMO. Additionally, the moving correlation between dust and Ca²⁺ in the Trambau ice core also aligns with the phase of the AMO, indicating that the AMO may influence the composition of dust in the Trambau ice core.