title: Freshwater fluxes in the Weddell Gyre: results from δ18O.
abstract: Full-depth measurements of δ(18)O 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 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.
authors.affiliation: British Antarctic Survey, Cambridge, UK School of Environmental Sciences, University of East Anglia, Norwich, UK p.j.brown@uea.ac.uk.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Brown
authors.affiliation: British Antarctic Survey, Cambridge, UK Scottish Association for Marine Science, Oban, UK.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Meredith
authors.affiliation: University of Southampton, National Oceanography Centre, Southampton, UK Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, USA.
authors.forename: Loïc
authors.initials: L
authors.lastname: Jullion
authors.affiliation: University of Southampton, National Oceanography Centre, Southampton, UK.
authors.forename: Alberto
authors.initials: A
authors.lastname: Naveira Garabato
authors.affiliation: National Oceanography Centre, Southampton, UK.
authors.forename: Sinhue
authors.initials: S
authors.lastname: Torres-Valdés
authors.affiliation: British Antarctic Survey, Cambridge, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Holland
authors.affiliation: NERC Isotope Geosciences Laboratory, Keyworth, UK Department of Geology, University of Leicester, Leicester, UK.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Leng
authors.affiliation: British Antarctic Survey, Cambridge, UK.
authors.forename: Hugh
authors.initials: H
authors.lastname: Venables
keywords: Antarctic Bottom Water; dense water export; freshwater cycle; oxygen isotope