Seasonality of downward carbon export in the Pacific Southern Ocean revealed by multi-year robotic observations

• Published in: Nature Communications
• Main Authors: Lacour, Léo, Llort, Joan, Briggs, Nathan, Strutton, Peter, G, Boyd, Philip, W
• Other Authors: Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Barcelona Supercomputing Center - Centro Nacional de Supercomputacion (BSC-CNS), National Oceanography Centre Southampton (NOC), University of Southampton, University of Tasmania Hobart (UTAS), L.L. was supported by a European Union’s Horizon 2020 Marie Sklodowska-Curie grant (no. 892653). Visits by L.L. to IMAS/UTas were supported by the Australian Research Council Special ResearchInitiative for Antarctic Gateway Partnership (Project ID SR140300001), the Australian Research Council Centre of Excellence for Climate System Science (Project ID B0018492), and the UTas visiting scholar program. J.L. was supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 754433. N.B. was supported by a European Research Council Consolidator Grant (GOCART, agreement number 724416). P.S. was supported by the Australian Research Council Centre of Excellence for Climate Extremes (Project ID CE170100023). P.W.B. was funded by the Australian Research Council by Laureate Fellowship FL160100131. We thank the Argo Data Management team (ADMT) and the BGC-Argo Data Management team (BGC ADMT). The specific float used in this study was funded by the ARC SRI for Antarctic Gateway Partnership (Project ID SR140300001).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Carbon cycle; Marine biology; [SDE]Environmental Sciences; Pacific; Southern Ocean
• Online Access: https://hal.science/hal-04018961; https://hal.science/hal-04018961v1/document; https://hal.science/hal-04018961v1/file/Lacour2023-Nature_Communications.pdf; https://doi.org/10.1038/s41467-023-36954-7

International audience At high latitudes, the biological carbon pump, which exports organic matter from the surface ocean to the interior, has been attributed to the gravitational sinking of particulate organic carbon. Conspicuous deficits in ocean carbon budgets challenge this as a sole particle export pathway. Recent model estimates revealed that particle injection pumps have a comparable downward flux of particulate organic carbon to the biological gravitational pump, but with different seasonality. To date, logistical constraints have prevented concomitant and extensive observations of these mechanisms. Here, using yearround robotic observations and recent advances in bio-optical signal analysis, we concurrently investigated the functioning of two particle injection pumps, the mixed layer and eddy subduction pumps, and the gravitational pump in Southern Ocean waters. By comparing three annual cycles in contrasting physical and biogeochemical environments, we show how physical forcing, phytoplankton phenology and particle characteristics influence the magnitude and seasonality of these export pathways, with implications for carbon sequestration efficiency over the annual cycle.