大気中酸素濃度の精密測定に基づくグローバル炭素収支の推定(企画総説「地球化学の最前線」)

概要

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Observation of the change in atmospheric O_2 concentration, combined with atmospheric CO_2 observation, provides complementary information about the global carbon cycle. This is based on the fact that O_2 and CO_2 fluxes are tightly coupled during terrestrial photosynthesis, respiration, and fossil fuel and biomass burning, but are less or decoupled during the sea-air gas exchanges. Especially, the long-term O_2 changes can be used to partition the sequestration of fossil fuel CO_2 release between ocean and terrestrial biosphere. In this review, we examine the parameters used for the partitioning calculation, including - O_2: C exchange ratios for the terrestrial photosynthesis/respiration and fossil fuel burning. In early atmospheric O_2 studies, the net oceanic O_2 flux was assumed to be zero because of the low solubility of O_2 in seawater in comparison with that of CO_2. However, recent studies have suggested that the upper-ocean warming, reducing the solubility of O_2 and the oceanic ventilation, causes net oceanic O_2 outgassing. We also review approaches to estimate the net oceanic O_2 fluxes. Finally, using the updated fossil CO_2 emission estimates and recently reported warming rates of the global upper ocean, we recalculate the ocean and terrestrial carbon sinks based on the previously reported atmospheric O_2 observations.
日本地球化学会の論文
2010-08-25