Freshwater fluxes in the Weddell Gyre: results from δ18O

• Published in: Nature Geoscience
• Main Authors: Brown, Peter J., Meredith, Michael P., Jullion, Loïc, Naveira Garabato, Alberto C., Torres-Valdés, Sinhue, Holland, Paul, J. Leng, Melanie, Venables, Hugh
• Other Authors: University of East Anglia Norwich (UEA), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), 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), National Oceanography Centre Southampton (NOC), University of Southampton, University of Leicester
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Southern Ocean; Weddell; Antarc*; Ice Sheet; Sea ice
• Online Access: https://hal.science/hal-01255782; https://doi.org/10.1038/ngeo102

International audience Full-depth measurements of δ18O from 2008 to 2010 enclosing the Weddell Gyre in the Southern Ocean are used to investigate the regional freshwater budget. Using complementary salinity, nutrients and oxygen data, a four-component mass balance was applied to quantify the relative contributions of meteoric water (precipitation/glacial input), sea-ice melt and saline (oceanic) sources. Combination of freshwater fractions with velocity fields derived from a box inverse analysis enabled the estimation of gyre-scale budgets of both freshwater types, with deep water exports found to dominate the budget. Surface net sea-ice melt and meteoric contributions reach 1.8% and 3.2%, respectively, influenced by the summer sampling period, and −1.7% and +1.7% at depth, indicative of a dominance of sea-ice production over melt and a sizable contribution of shelf waters to deep water mass formation. A net meteoric water export of approximately 37 mSv is determined, commensurate with local estimates of ice sheet outflow and precipitation, and the Weddell 2 Gyre is estimated to be a region of net sea-ice production. These results constitute the first synoptic benchmarking of sea-ice and meteoric exports from the Weddell Gyre, against which future change associated with an accelerating hydrological cycle, ocean climate change and evolving Antarctic glacial mass balance can be determined.