Input and output fluxes of surface CO2 throughout the lower Cenozoic

Long-term Cenozoic climate trends result from changes in the geological carbon cycle and associated surface input and output CO₂ fluxes largely due to magmatic emissions and weathering of silicate minerals (Berner & Lasaga, 1989). Proxy records allow to detect absolute values of CO₂ in different reservoirs to define major Cenozoic climatic events (e.g., PETM, EECO or MECO). However, interpreting the proxy-based time history of surface CO₂ budget in terms of input and output CO₂ fluxes is critical to assess the responsible processes behind the surface-deep carbon exchange and associated long term climate trends. Here, we use a newly developed technique (Castrogiovanni et al., 2024) based on a reversible-jump Markov chain Monte Carlo algorithm (rj-McMC) to invert the CO₂ time series from the Proxy Integration Project (CENCO₂PIP) (Hönisch et al., 2023) and obtain estimates of the surface input and output CO₂ fluxes throughout the lower Cenozoic. We base the inversion on a general formulation of the geological carbon cycle and use the temperature time history from Hansen et al., 2023 as a further constraint to the inversion scheme. Results indicate a marked peak in the emission rate of CO₂ at ˜56 Ma (PETM), enhanced CO₂ emissions between 54-50 Ma (EECO) and at ˜40 Ma (MECO), whereas the output CO₂ term associated to weathering responds to such variations of the input CO₂ term. We conclude that magmatic CO₂ emissions related to the closure of the Neo-Tethyan ocean and opening of the Nort-East Atlantic Ocean played a key role in driving lower Cenozoic climate trends.

 

References

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Castrogiovanni, L., Sternai, P., Piana Agostinetti, N., & Pasquero, C. (2024). A reversible-jump Markov chain Monte Carlo algorithm to estimate paleo surface CO2 fluxes linking temperature to atmospheric CO2 concentration time series. Computers & Geosciences, 105838. https://doi.org/10.1016/J.CAGEO.2024.105838

Hansen, J. E., Sato, M., Simons, L., Nazarenko, L. S., Sangha, I., Kharecha, P., Zachos, J. C., von Schuckmann, K., Loeb, N. G., Osman, M. B., Jin, Q., Tselioudis, G., Jeong, E., Lacis, A., Ruedy, R., Russell, G., Cao, J., & Li, J. (2023). Global warming in the pipeline. Oxford Open Climate Change, 3 (1). https://doi.org/10.1093/OXFCLM/KGAD008

Hönisch, B., Royer, D. L., Breecker, D. O., Polissar, P. J., Bowen, G. J., Henehan, M. J., Cui, Y., Steinthorsdottir, M., McElwain, J. C., Kohn, M. J., Pearson, A., Phelps, S. R., Uno, K. T., Ridgwell, A., Anagnostou, E., Austermann, J., Badger, M. P. S., Barclay, R. S., Bijl, P. K., … Zhang, L. (2023). Toward a Cenozoic history of atmospheric CO2. Science, 382 (6675). https://doi.org/10.1126/SCIENCE.ADI5177/SUPPL_FILE/SCIENCE.ADI5177_SM.PDF