日本地球惑星科学連合2023年大会

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[J] 口頭発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS09] 生物地球化学

2023年5月23日(火) 13:45 〜 15:00 105 (幕張メッセ国際会議場)

コンビーナ:福島 慶太郎(福島大学農学群食農学類)、木庭 啓介(京都大学生態学研究センター)、大河内 直彦(海洋研究開発機構)、山下 洋平(北海道大学 大学院地球環境科学研究院)、座長:木庭 啓介(京都大学生態学研究センター)、福澤 加里部(北海道大学北方生物圏フィールド科学センター)

13:45 〜 14:00

[MIS09-01] 太平深層に分布する深海熱水由来の熱成炭素

*山下 洋平1,2、森 雄太郎2、小川 浩史3 (1.北海道大学 大学院地球環境科学研究院、2.北海道大学 大学院環境科学院、3.東京大学 大気海洋研究所)

キーワード:海洋、熱水、溶存有機物、熱成炭素、溶存黒色炭素

Pyrogenic carbon, a byproduct of biomass and fossil fuel combustion, is an important component in global carbon cycle because it can be stored on Earth’s surface for centuries to millennia. A part of pyrogenic carbon become dissolvable with oxidation. The dissolvable fraction of pyrogenic carbon is called dissolved black carbon (DBC). DBC is known to occur ubiquitously in the ocean. Although recent studies clarified that DBC in the deep ocean is removed via sorption onto sinking particles, the DBC cycle and budget in the ocean have not been well constrained. In particular, the missing source has been suggested by imbalance of the budget in the ocean. Deep hydrothermal vents are suggested to be a possible source of thermogenic DBC, but little is known about the distribution of hydrothermal DBC in the deep ocean. Here, we show the basin-scale distributions of DBC along two transects in the eastern Pacific Ocean. The concentration and condensation degree of deep ocean DBC at the sites close to the Eastern Pacific Rise were higher than those at the other sites, suggesting that highly condensed DBC was derived from hydrothermal systems and transported over long distances. The hydrothermal DBC concentration was quantified as a deviation from the linear relationship between the DBC concentration and apparent oxygen utilization previously observed in the central and western Pacific Ocean. The deviation was linearly correlated with excess 3He, a tracer of hydrothermal input, confirming the hydrothermal origin of the DBC. Our tentative estimate of global hydrothermal DBC fluxes, 1.6–9.7 TgC/year, corresponded to 8.9 to 53.9% of the riverine DBC flux to the ocean.