Tracing water masses with 129I and 236U in the subpolar North Atlantic along the GEOTRACES GA01 section

• Published in: Biogeosciences
• Main Authors: Castrillejo, Maxi, Casacuberta, Núria, Christl, Marcus, Vockenhuber, Christof, Synal, Hans-Arno, García-Ibáñeza, Maribel I., Lherminier, Pascale, Sarthou, Géraldine, Garcia-Orellanac, Jordi, Masqué, Pere
• Other Authors: Department of Physics = Departement Physik ETH Zürich (D-PHYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), Institut de Ciencia i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona = Autonomous University of Barcelona = Universidad Autónoma de Barcelona (UAB), Institute of Biogeochemistry and Pollutant Dynamics ETH Zürich (IBP), Department of Environmental Systems Science ETH Zürich (D-USYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich)-Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Centro de Investigaciones Biológicas (CSIC), Consejo Superior de Investigaciones Cientificas = Spanish National Research Council (CSIC), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 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), Edith Cowan University (ECU), ANR-12-PDOC-0025,BITMAP,Biodisponibilité du fer et des métaux traces dans les particules marines(2012), 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-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: FUEL-REPROCESSING FACILITIES; WESTERN BOUNDARY CURRENT; STRAIT OVERFLOW WATER; DENMARK STRAIT; ARCTIC-OCEAN; NORDIC SEAS; DEEP-WATER; ANTHROPOGENIC U-236; GEOVIDE CRUISE; DEPTH PROFILE; ACL; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Arctic Ocean; Greenland; Denmark Strait; East Greenland; east greenland current; Iceland; Nordic Seas; North Atlantic
• Online Access: https://hal.science/hal-02322755; https://hal.science/hal-02322755/document; https://hal.science/hal-02322755/file/Castrillejo_etal_BG_2018.pdf; https://doi.org/10.5194/bg-15-5545-2018

International audience Pathways and timescales of water mass transport in the subpolar North Atlantic Ocean (SPNA) have been investigated by many studies due to their importance for the meridional overturning circulation and thus for the global ocean. In this sense, observational data on geochemical trac-ers provide complementary information to improve the current understanding of the circulation in the SPNA. To this end, we present the first simultaneous distribution of artificial 129 I and 236 U in 14 depth profiles and in surface waters along the GEOVIDE section covering a zonal transect through the SPNA in spring 2014. Our results show that the two tracers are distributed following the water mass structure and that their presence is largely influenced by the global fallout (GF) and liquid effluents discharged to northwestern European coastal waters by the Sellafield and La Hague nuclear reprocessing plants (NRPs). As a result, 129 I concentrations and 236 U/ 238 U atom ratios and 129 I/ 236 U atom ratios display a wide range of values: (0.2-256) ×10 7 at kg −1 (40-2350) ×10 −12 and 0.5-200, respectively. The signal from NRPs, which is characterised by higher 129 I concentrations and 129 I/ 236 U atom ratios compared to GF, is transported by Atlantic Waters (AWs) into the SPNA, notably by the East Greenland Current (EGC)/Labrador Current (LC) at the surface and by waters overflowing the Greenland-Scotland passage at greater depths. Nevertheless, our results show that the effluents from NRPs may also directly enter the surface of the eastern SPNA through the Iceland-Scotland passage or the English Channel/Irish Sea. The use of the 236 U/ 238 U and 129