[M-IS14] 生物地球化学

[MIS14-02] 海洋における溶存黒色炭素の除去過程

*山下 洋平^1,2、中根 基裕²、森 雄太郎²、西岡 純^3,2、小川 浩史⁴ (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.北海道大学 低温科学研究所、4.東京大学 大気海洋研究所)

キーワード：熱成炭素、海洋溶存有機物、溶存黒色炭素

Pyrogenic carbon (PyC), a byproduct of biomass and fossil fuel combustion, may control the climate because it can be stored on Earth’s surface for centuries to millennia. PyC produced on land is transferred to the ocean through riverine inputs and atmospheric deposition. Dissolvable BC, often denoted as dissolved BC (DBC), ubiquitously occurs in the ocean, and the ocean possibly acts as an ultimate PyC sink. Currently, however, we lack a full understanding of PyC cycling on Earth’s surface because the fate of DBC in the ocean has not been constrained. Here, we show the first basin-scale distribution of DBC in the Pacific Ocean and find that the DBC concentrations in the deep Pacific decrease along with deep-ocean meridional circulation. The DBC concentration is negatively correlated with apparent oxygen utilization, a proxy of the integrated flux of sinking particles, in the deep Pacific, implying that DBC is removed from the deep ocean to abyssal sediments through adsorption onto sinking particles. The burial flux of DBC to abyssal sediments is estimated to be 0.040–0.085 PgC yr-1, corresponding to 15–33% of the global PyC produced by landscape fires and 1.5–3.3% of the anthropogenic CO2 uptake by the ocean.