日本地球惑星科学連合2023年大会

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[J] オンラインポスター発表

セッション記号 A (大気水圏科学) » A-AS 大気科学・気象学・大気環境

[A-AS07] 大気化学

2023年5月23日(火) 09:00 〜 10:30 オンラインポスターZoom会場 (3) (オンラインポスター)

コンビーナ:坂本 陽介(京都大学大学院地球環境学堂)、内田 里沙(一般財団法人 日本自動車研究所)、石戸谷 重之(産業技術総合研究所)、岩本 洋子(広島大学大学院統合生命科学研究科)

現地ポスター発表開催日時 (2023/5/22 17:15-18:45)

09:00 〜 10:30

[AAS07-P01] Interannual variations in delta(APO) and delta(Ar/N2) observed at four Japanese stations for the period 2012-2022

*石戸谷 重之1遠嶋 康徳2村山 昌平1丹羽 洋介2石島 健太郎3、菅原 敏4坪井 一寛3、青木 伸行1 (1.産業技術総合研究所、2.国立環境研究所、3.気象研究所、4.宮城教育大学)

キーワード:大気ポテンシャル酸素、大気中アルゴン濃度、年々変動

Atmospheric Potential Oxygen (APO=O2+1.1xCO2) (delta(APO)) varies due to air-sea O2, N2 and CO2 fluxes and fossil fuel O2 and CO2 fluxes, while atmospheric Ar/N2 ratio (delta(Ar/N2)) varies due only to air-sea Ar and N2 fluxes. It has been reported by past studies that seasonal and interannual variations in delta(APO) are driven mainly by the air-sea O2 and N2fluxes, although the air-sea CO2 and fossil fuel fluxes cause a secular delta(APO) trend (e.g. Tohjima et al., 2019; Ishidoya et al., 2021). As to the air-sea exchange, Ar and N2 fluxes are driven by solubility change, and O2 flux is driven by both solubility and biospheric changes. Therefore, it is expected that we can separate an interannual variation in delta(APO) due to the solubility change (delta(APO)therm) from that to the net marine biological activities (delta(APO)netbio) by a combined analysis of delta(APO) and delta(Ar/N2). We have conducted simultaneous observations of delta(APO) and delta(Ar/N2) at various observational sites, and the data longer periods than 10 years have been obtained at Tsukuba (36°N, 140°E), Hateruma Island (24°N, 124°E), Cape Ochiishi (43°N, 146°E), and Takayama (36°N, 137°E), Japan (updated from Ishidoya et al., 2021). The annual change rate of the average delta(APO)therm at the four sites, obtained by multiplying a coefficient of 0.9 derived from differences in the solubility in O2 and Ar (Weiss, 1970), was found to vary in phase with the Southern Oscillation Index (SOI) and the annual change rate of the global ocean heat content. On the other hand, the corresponding annual change rate of the average delta(APO)netbio, obtained by subtracting the rate of delta(APO)therm from delta(APO) (small contributions of the air-sea CO2 and fossil fuel fluxes are also subtracted based on a simulation using an atmospheric transport model), varied in opposite phase with SOI. These responses of delta(APO)therm and delta(APO)netbio to El Niño / La Niña events are qualitatively consistent with those expected from the simulations based on a community earth system model by Eddebbar et al. (2017).

Acknowledgements
We thank staff of Global Environmental Forum (GEF) for their works to collect the air samples at Hateruma and Ochiishi stations. This study was partly supported by the JSPS KAKENHI (grant nos. 22H05006, 19H01975 and 15H02814) and the Global Environment Research Coordination System from the Ministry of the Environment, Japan (grant nos. METI1454 and METI1953).

References
Eddebbar, Y. A., et al., Impacts of ENSO on air-sea oxygen exchange: Observations and mechanisms, Global Biogeochem. Cy., 31, 901–921, 2017.
Ishidoya, S., et al., Secular change in atmospheric Ar/N2 and its implications for ocean heat uptake and Brewer-Dobson circulation, Atmos. Chem. Phys., 21, 1357-1373, 2021.
Ishidoya, S., et al., Spatiotemporal variations of the delta(O2/N2), CO2 and delta(APO) in the troposphere over the Western North Pacific, Atmos. Chem. Phys., 22, 6953–6970, 2022.
Tohjima, Y., et al., Global carbon budgets estimated from atmospheric O2/N2 and CO2 observations in the western Pacific region over a 15-year period, Atmos. Chem. Phys., 19, 9269–9285, 2019.
Weiss, R. F., The solubility of nitrogen, oxygen and argon in water and seawater, Deep-Sea Res., 17, 721–735, 1970.