Subduction of carbon, nitrogen, and oxygen in the northeast Atlantic

• Published in: Journal of Geophysical Research
• Main Authors: Karleskind, Pierre, Lévy, Marina, Mémery, Laurent
• Other Authors: Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), CNRS-INSU (POMME and TWISTED programs)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: POMME experiment; phytoplankton bloom; mode water; carbon pump; flux; export; envir; geo; Northeast Atlantic
• Online Access: https://doi.org/10.1029/2010JC006446; https://hal.univ-brest.fr/hal-00634525/file/JGR-Karlesking-2011.pdf; https://hal.univ-brest.fr/hal-00634525

International audience Northeast Atlantic mode waters (NEAMW) are formed by subduction in a region known to be a strong sink of atmospheric CO2. This study investigates the biological and physical carbon pumps involved in this sink. For that purpose, we estimate the annual transfer of carbon, nitrogen, and oxygen from the surface into the ocean interior through NEAMW subduction. Our estimates are based on a model simulation constrained with data collected during the Programme Océan Multidisciplinaire Méso Echelle (POMME). We found that subduction accounts for a large proportion of carbon export below the mixed layer in the POMME region (38°N-45°N, 16°W-22°W). Fifty percent of labile organic carbon is exported by the biological pump and 50% by subduction; 98% of the total carbon flux below the mixed layer is due to carbon subduction, essentially in the form of dissolved inorganic carbon and of more refractory dissolved organic matter. This is because they are the dominant pools of carbon and are passing through the winter mixed-layer depth gradient that characterizes the region. Our results emphasize that the net export of carbon represents a small fraction of the fluxes of carbon across the mixed layer through the processes of subduction and obduction. Moreover, our results indicate that NEAMW subduction occurs before the spring bloom. This implies that NEAMW is mostly subducted with end-winter characteristics with, in particular, relatively high nutrient content. This reflects a relative inefficiency in nutrient utilization and contrasts with subtropical mode waters, which are subducted during the bloom and are thus relatively poor in nutrients when they are subducted.