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Article Dans Une Revue Climate of the Past Année : 2009

Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum

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We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO 2 at the last glacial maximum (LGM). We examine 5 different re-alisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton physiology at the LGM. Measured changes in carbon-13 and carbon-14, as well as a qualitative reconstruction of the change in ocean carbon export are used to evaluate the results. Overall, we find that while a reduction in ocean ventilation at the LGM is necessary to reproduce carbon-13 and carbon-14 observations, this circulation results in a low net sink for atmospheric CO 2. In contrast, while biogeochemical processes contribute little to carbon isotopes, we propose that most of the change in atmospheric CO 2 was due to such factors. However, the lesser role for circulation means that when all plausible factors are accounted for, most of the necessary CO 2 change remains to be explained. This presents a serious challenge to our understanding of the mechanisms behind changes in the global carbon cycle during the geologic past.
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hal-02891933 , version 1 (28-07-2020)

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A. Tagliabue, L. Bopp, Didier M. Roche, N. Bouttes, J.-C. Dutay, et al.. Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum. Climate of the Past, 2009, 5 (4), pp.695-706. ⟨10.5194/cp-5-695-2009⟩. ⟨hal-02891933⟩
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