AtlantECO Deliverable - D06.6 - Report on the quantification, mechanisms and impacts of the carbon export in the Atlantic Ocean

Le résumé fourni par la source

This report explores the complexities of carbon export at the Atlantic scale, incorporating in situ observations and numerical models, with a focus on the Benguela region that was chosen as a target area for AtlantECO. A major challenge is the lack of a unified definition of carbon export due to differing methodologies. The report recommends reporting relative values, emphasizing transfer efficiency in the mesopelagic layer. Seasonal variations significantly influence carbon cycling, with mixing and advective transport playing crucial roles. In particular, mixing significantly enhances the transfer efficiency compared to estimates using the gravitational pump flux alone. The analysed deep sediment trap data reveal substantial seasonal flux variations, while BGC-Argo estimates suggest lower export levels than reported in the literature likely due to mixing-driven variability. The Benguela system poses unique challenges for reconciling carbon export estimates. The Lagrangian approach demonstrated that mesoscale processes and the migratory biogeochemical pump influence organic matter transport, with most remineralization occurring near the 200 m isobath. AtlantECO’s new coupled physical-biogeochemical model based on NEMO-BFM enhances the understanding of Benguela’s carbon cycling. The work considers the paradox of the Benguela acting as a CO₂ sink despite its productivity. Long-term organic carbon flux data suggest significant lateral transport across the western boundary into the South Atlantic, confirming the basin-scale contribution of the Benguela region despite the paradox. This report underscores the necessity of methodological harmonization in carbon export studies, highlighting the importance of improved observational constraints and refined modelling approaches to better quantify regional and basin-scale carbon dynamics.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.