日本地球惑星科学連合2023年大会

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[E] 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-CG 大気海洋・環境科学複合領域・一般

[A-CG35] グローバル炭素循環の観測と解析

2023年5月26日(金) 09:00 〜 10:30 オンラインポスターZoom会場 (1) (オンラインポスター)

コンビーナ:市井 和仁(千葉大学)、Patra Prabir(Research Institute for Global Change, JAMSTEC)、伊藤 昭彦(国立環境研究所)

現地ポスター発表開催日時 (2023/5/25 17:15-18:45)

09:00 〜 10:30

[ACG35-P01] Global carbon budgets for a recent two decadal period based on atmospheric O2 and CO2 observations in the western Pacific region

*遠嶋 康徳1笹川 基樹1中岡 慎一郎1寺尾 有希夫1坪井 一寛2、向井 人史1町田 敏暢1 (1.国立環境研究所、2.気象研究所)

キーワード:全球炭素収支、大気中酸素、大気中二酸化炭素

We present global ocean and land carbon sequestration rates for a recent two decadal period based on measurements of the atmospheric O2/N2 ratio and CO2 mole fractions of air samples collected in the western Pacific region. The air samples have been collected into glass flasks at Hateruma Island (HAT; lat. 24.1°N, long. 123.8°E) since July 1997, at Cape Ochi-ishi (COI; lat. 43.2°N, long. 145.5°E) since December 1999, at Minamitorishima (MNM; lat. 24.3°N, long. 154.0°E) since September 2011, and onboard cargo ships on regular roundtrip cruises to North America and to New Zealand/Australia since December 2001. Combining the O2/N2 ratio and CO2 mole fraction, we computed a value of atmospheric potential oxygen (APO=O2+β×CO2) for each sample, where β represents the −O2/CO2 exchange ratios for the land biosphere. The partitioning of the global ocean and land carbon sinks were evaluated by solving simultaneous budget equations of the APO and the atmospheric CO2. In accordance with the previous study (Tohjima et al., 2019), we used the global CO2 data derived from the NOAA/ESRL observation network and net ocean O2 outgassing flux estimated from the change in the ocean heat content (0-2000m). Note that we corrected O2/N2 data of this study for the difference in the span sensitivity from the gravimetric scale (Aoki et al., 2021) and used a value of 1.05 for β.
The resulting average global ocean and land carbon sequestration rates for the 22-year period from 2000 to 2021 were 2.9 ± 0.7 PgC yr−1 and 1.4 ± 1.0 PgC yr−1, respectively. To examine the temporal trend in the sequestration rates, we computed those for an interval of 5-year period, which effectively reduced apparent variations in the sequestration rates derived probably from the imbalances between seasonal ocean O2 outgassing and ingassing fluxes. The consecutive 5-year ocean sequestration rates showed an increasing trend at a rate of 0.08 ± 0.01 PgC yr−2 during 2001-2019. In contrast, the relatively large land sequestration rate of 1.9 ± 0.3 PgC yr−1 during 2004-2013 decreased to that of 1.3 ± 0.3 PgC yr−1 during 2014-2019.