The 226Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

• Published in: Biogeosciences
• Main Authors: Le Roy, Emilie, Sanial, Virginie, Charette, Matthew, van Beek, Pieter, Lacan, Francois, Jacquet, Stéphanie, Henderson, Paul, Souhaut, Marc, García-Ibáñez, Maribel, Catherine, Jeandel, Pérez, Fiz, Sarthou, Géraldine
• Other Authors: Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Department of Marine Chemistry and Geochemistry (WHOI), Woods Hole Oceanographic Institution (WHOI), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Spanish National Research Council (CSIC), 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 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)-Centre National de la Recherche Scientifique (CNRS), ANR-13-BS06-0014,GEOVIDE,GEOVIDE, Une étude internationale GEOTRACES le long de la section OVIDE en Atlantique Nord et en Mer du Labrador(2013), ANR-12-PDOC-0025,BITMAP,Biodisponibilité du fer et des métaux traces dans les particules marines(2012), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: RADIUM; PACIFIC; ACL; BARITE FORMATION; THORIUM ISOTOPES; ISOTOPE-DILUTION; ANTARCTIC OCEAN; BA CONCENTRATIONS; MARINE GEOCHEMISTRY; WATER MASSES; WESTERN MEDITERRANEAN SEA; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Antarctic; Antarctic Ocean; Canada; Greenland; Pacific; West European Basin; Antarc*; North Atlantic; Northeast Atlantic
• Online Access: https://hal.science/hal-02511004; https://hal.science/hal-02511004/document; https://hal.science/hal-02511004/file/Le%20Roy%20et%20al.%202018%20HAL.pdf; https://doi.org/10.5194/bg-15-3027-2018

International audience We report detailed sections of radium-226 (226 Ra, T 1/2 = 1602 years) activities and barium (Ba) concentrations determined in the North Atlantic (Portugal-Greenland-Canada) in the framework of the international GEO-TRACES program (GA01 section-GEOVIDE project, May-July 2014). Dissolved 226 Ra and Ba are strongly correlated along the section, a pattern that may reflect their similar chemical behavior. Because 226 Ra and Ba have been widely used as tracers of water masses and ocean mixing, we investigated their behavior more thoroughly in this crucial region for thermohaline circulation, taking advantage of the contrasting biogeochemical patterns existing along the GA01 section. We used an optimum multiparameter (OMP) analysis to distinguish the relative importance of physical transport (water mass mixing) from nonconservative processes (sedimentary, river or hydrothermal inputs, uptake by particles and dissolved-particulate dynamics) on the 226 Ra and Ba distributions in the North Atlantic. Results show that the measured 226 Ra and Ba concentrations can be explained by conservative mixing for 58 and 65 % of the samples, respectively , notably at intermediate depth, away from the ocean interfaces. 226 Ra and Ba can thus be considered conservative tracers of water mass transport in the ocean interior on the space scales considered here, namely, on the order of a few thousand kilometers. However, regions in which 226 Ra and Ba displayed nonconservative behavior and in some cases de-coupled behaviors were also identified, mostly at the ocean boundaries (seafloor, continental margins and surface waters). Elevated 226 Ra and Ba concentrations found in deep-water in the West European Basin suggest that lower Northeast Atlantic Deep Water (NEADWl) accumulates 226 Ra and Ba from sediment diffusion and/or particle dissolution during transport. In the upper 1500 m of the West European Basin, deficiencies in 226 Ra and Ba are likely explained by their incorporation in planktonic calcareous and ...