A publication in Nature Geoscience

Carbon sequestration by the biological pump is not exclusive to the deep ocean



A study carried out by Florian Ricour - as part of his joint thesis between the MAST laboratory at the University of Liège and the Villefranche-sur-Mer Oceanographic Laboratory (Sorbonne University, France) - shows that carbon sequestration by the biological pump is not restricted to the deep ocean and can occur at any depth in the water column. This study has been published in the journal Nature Geoscience.

T

he carbon sink formed by the ocean contains the equivalent of forty times the quantity of CO2 in the atmosphere. The biological carbon pump plays a key part in carbon sequestration by transporting organic carbon from the ocean surface to deep waters via three processes: the fall of organic particles into the water column, the vertical migration of organisms and physical circulation.

While it was thought that sequestration only occurred in the deep ocean, beyond a depth of 1,000 m, a study carried out by Florian Ricour as part of his joint thesis with the ULiège MAST laboratory (under the supervision of Marilaure Grégoire) and the Villefranche-sur-Mer Oceanographic laboratory, proposes a new scheme for sequestration by the biological pump. Our study shows that carbon sequestration can occur throughout the water column," explains Florian Ricour, the paper's first author. As a result, we have calculated that carbon sequestration fluxes by the biological pump on a timescale of a century would be up to six times higher than those estimated until now. This concept of 'continuous vertical sequestration (CONVERSE), therefore, shows that carbon sequestration on the scale of a century occurs above a depth of 1,000 metres in many oceanic regions.

This reassessment of carbon sequestration fluxes by the biological pump for at least 100 years using the CONVERSE method shows not only that these fluxes are higher than previously thought but also that vertical migration and physical circulation, which are generally neglected, make a significant contribution (20 to 30%). The century-scale carbon sequestration flux calculated by the CONVERSE method provides a new metric for the biological pump. This metric should be used in the future to diagnose changes in carbon sequestration fluxes in prognostic models of ocean biogeochemistry.

Biological pump ©Laetitia Drago

Illustration of the concept of continuous carbon sequestration by the biological pump. ©Laetitia Drago.

Scientific references

Ricour, F., Guidi, L., Gehlen, M. et al. Century-scale carbon sequestration flux throughout the ocean by the biological pump. Nat. Geosci. 16, 1105-1113 (2023). doi.org/10.1038/s41561-023-01318-9

Contact

Florian Ricour

Marilaure Grégoire

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