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  • Distributions, sources, and...
    Marsay, Chris M.; Barrett, Pamela M.; McGillicuddy, Dennis J.; Sedwick, Peter N.

    Journal of geophysical research. Oceans, August 2017, 20170801, Letnik: 122, Številka: 8
    Journal Article

    We report water column dissolved iron (dFe) and particulate iron (pFe) concentrations from 50 stations sampled across the Ross Sea during austral summer (January–February) of 2012. Concentrations of dFe and pFe were measured in each of the major Ross Sea water masses, including the Ice Shelf Water and off‐shelf Circumpolar Deep Water. Despite significant lateral variations in hydrography, macronutrient depletion, and primary productivity across several different regions on the continental shelf, dFe concentrations were consistently low (<0.1 nM) in surface waters, with only a handful of stations showing elevated concentrations (0.20–0.45 nM) in areas of melting sea ice and near the Franklin Island platform. Across the study region, pFe associated with suspended biogenic material approximately doubled the inventory of bioavailable iron in surface waters. Our data reveal that the majority of the summertime iron inventory in the Ross Sea resides in dense shelf waters, with highest concentrations within 50 m of the seafloor. Higher dFe concentrations near the seafloor are accompanied by an increased contribution to pFe from authigenic and/or scavenged iron. Particulate manganese is also influenced by sediment resuspension near the seafloor but, unlike pFe, is increasingly associated with authigenic material higher in the water column. Together, these results suggest that following depletion of the dFe derived from wintertime convective mixing and sea ice melt, recycling of pFe in the upper water column plays an important role in sustaining the summertime phytoplankton bloom in the Ross Sea polynya. Key Points Summertime dissolved and particulate iron concentrations are reported for all Ross Sea water masses and off‐shelf Circumpolar Deep Water Summertime inventories of dissolved iron and particulate trace elements are strongly influenced by high concentrations near the seafloor Surface water concentrations of bioavailable iron are approximately doubled if biogenic pFe is considered along with dFe concentrations