Carbon dynamics of the Weddell Gyre, Southern Ocean

• Published in: Global Biogeochemical Cycles
• Main Authors: Brown, Peter, J., Jullion, Loïc, Landschützer, Peter, Bakker, Dorothee C. E., Naveira Garabato, Alberto C., Meredith, Michael P., Torres-Valdés, Sinhue, Watson, Andrew J., Hoppema, Mario, Loose, Brice, Jones, Elizabeth, M., Telszewski, Maciej, Jones, Steve, D., Wanninkhof, Rik
• Other Authors: National Oceanography Centre Southampton (NOC), University of Southampton, 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), 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), University of East Anglia Norwich (UEA), Nathional Oceanography Centre, British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI), Helmholtz-Gemeinschaft = Helmholtz Association, University of Rhode Island, University of Rhode Island (URI), Royal Netherlands Institute for Sea Research (NIOZ), International Ocean Carbon Coordination Project, NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML), National Oceanic and Atmospheric Administration (NOAA), European Project: GOCE-511176-1
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Southern Ocean; Weddell Sea; Weddell
• Online Access: https://hal.science/hal-01254978; https://hal.science/hal-01254978/document; https://hal.science/hal-01254978/file/Global%20Biogeochem%20Cy_Brown_2015.pdf; https://doi.org/10.1002/2014GB005006

International audience The accumulation of carbon within the Weddell Gyre and its exchanges across the gyre boundaries are investigated with three recent full-depth oceanographic sections enclosing this climatically important region. The combination of carbon measurements with ocean circulation transport estimates from a box inverse analysis reveals that deepwater transports associated with Warm Deep Water (WDW) and Weddell Sea Deep Water dominate the gyre's carbon budget, while a dual-cell vertical overturning circulation leads to both upwelling and the delivery of large quantities of carbon to the deep ocean. Historical sea surface pCO 2 observations, interpolated using a neural network technique, confirm the net summertime sink of 0.044 to 0.058 ± 0.010 Pg C yr À1 derived from the inversion. However, a wintertime outgassing signal similar in size results in a statistically insignificant annual air-to-sea CO 2 flux of 0.002 ± 0.007 Pg C yr À1 (mean 1998–2011) to 0.012 ± 0.024 Pg C yr À1 (mean 2008–2010) to be diagnosed for the Weddell Gyre. A surface layer carbon balance, independently derived from in situ biogeochemical measurements, reveals that freshwater inputs and biological drawdown decrease surface ocean inorganic carbon levels more than they are increased by WDW entrainment, resulting in an estimated annual carbon sink of 0.033 ± 0.021 Pg C yr À1. Although relatively less efficient for carbon uptake than the global oceans, the summertime Weddell Gyre suppresses the winter outgassing signal, while its biological pump and deepwater formation act as key conduits for transporting natural and anthropogenic carbon to the deep ocean where they can reside for long time scales.