日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 A (大気水圏科学) » A-OS 海洋科学・海洋環境

[A-OS12] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

2019年5月27日(月) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:伊藤 進一(東京大学大気海洋研究所)、平田 貴文(北海道大学地球環境科学研究院)、Enrique N Curchitser(Rutgers University New Brunswick)、Eileen E Hofmann(Old Dominion University)

[AOS12-P02] Revisiting vertical variations in stoichiometry during oceanic organic matter decomposition

*重光 雅仁1青山 道夫1土居 知将 1横川 太一1村田 昌彦1 (1.国立研究開発法人 海洋研究開発機構)

キーワード:栄養塩、化学量論比、有機物分解

Using the new global nutrient data set, we re-evaluate basin-wide stoichiometric ratios of remineralization estimated by Anderson and Sarmiento (1994) (hereinafter, AS94). For the same latitudinal ranges of the Atlantic, Indian and Pacific Oceans as in AS94, we construct one or two end-member mixing models on 14 neutral surfaces and estimate the stoichiometric ratios with a probabilistic approach. Unlike the results of AS94, significant vertical variations in the stoichiometry are found in the Atlantic and Pacific, while relatively constant stoichiometry with depth is found in the Indian Ocean, similar to AS94. The decreases in the C/P and –O2/P ratios with depth in the Atlantic could be caused via dark DIC fixation by chemoautotrophs in the deep waters. In the Pacific, changes in organic matter composition with depth would be the most important factor in the increases in stoichiometry with depth. In all the basins, the N/P ratios are probably affected by benthic denitrification, as in AS94. The P/C/-O2ratios (mean and 5thto 95thpercentile) are estimated to be 1/111(97 to 129)/155(149 to 163) in the depths below 2000 m of the Indian and Pacific Oceans, where DIC fixation and vertical change in organic matter composition have little influence on the stoichiometry estimates. We suggest that chemoautotrophic DIC fixation and the effect of change in organic matter composition with depth on the stoichiometry in waters above 2000 m should be considered for large-scale biogeochemical modeling and estimation of oceanic uptake of anthropogenic carbon from observational data.