日本地球惑星科学連合2021年大会

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セッション記号 A (大気水圏科学) » A-CC 雪氷学・寒冷環境

[A-CC26] アイスコアと古環境モデリング

2021年6月3日(木) 15:30 〜 17:00 Ch.13 (Zoom会場13)

コンビーナ:竹内 望(千葉大学)、阿部 彩子(東京大学大気海洋研究所)、植村 立(名古屋大学 環境学研究科)、川村 賢二(情報・システム研究機構 国立極地研究所)、座長:竹内 望(千葉大学)、植村 立(名古屋大学 環境学研究科)

15:30 〜 15:45

[ACC26-07] ドームふじ基地の日降水同位体比に大規模大気循環が与える影響: 同位体気候モデルMIROC5-isoを用いた研究

*木野 佳音1,2、岡崎 淳史3、Alexandre Cauquoin2、芳村 圭2 (1.東京大学大気海洋研究所、2.東京大学生産技術研究所、3.ペンシルバニア州立大学)


キーワード:気候モデル、水同位体、アイスコア、古気候プロキシ、南極

Thanks to water isotope records in polar ice cores, it has been possible to study past Earth’s climate variations at different time scales. However, the different contributions at regional and global scales determining the isotopic signal in these ice cores are still unclear. The observations at Dome Fuji Station, inland East Antarctica, and further analyses of weather situations have investigated the relationship between δ18O of daily precipitation (δ18Op) and the synoptic precipitation events, which are mostly accompanied by increased temperature [1,2], whereas the climatic understanding is not established.

One way to progress our understanding of the question is to make direct comparisons of isotopic data with simulation results from isotope-enabled General Circulation Models (GCMs). We here used such a model, the Japanese atmospheric GCM MIROC5-iso [3], and conducted a simulation with the horizontal winds nudged to the JRA-25 reanalysis [4] for 1981-2010. The simulation nicely reproduces the observed δ18Op at Dome Fuji, as well as the synoptic precipitation events.

We reveal that the large-scale atmospheric circulation variations, specifically related to the Southern Annular Mode, significantly affect the δ18Op at Dome Fuji during cold seasons (austral autumn, winter, and spring). This is because the advection of the warm air largely changes the local temperature and δ18Op, supporting previous studies [1]. However, in the austral summer, the contribution of the precipitation amounts relatively large for the variability of δ18Op, while temperature rise affects only a little the δ18Op signal.

Our result suggests the water isotopes in the ice cores do not capture the whole variations of local temperature, and precipitation events contribute to a warm bias in the cold seasons. Interpretation for past climate situations (e.g. Last Glacial Maximum) will be further investigated.

[1] Fujita and Abe, Geophys. Res. Lett., 33, L18503, 2006.
[2] Dittman et al., Atmos. Chem. Phys., 16, 6883-6900, 2016.
[3] Okazaki and Yoshimura, J. Geophys. Res. Atmos, 124, 8972–8993, 2019.
[4] Onogi et al., J. Meteor. Soc. Japan, 85(3), 369-432, 2007.