Natural iron fertilization of the Atlantic sector of the Southern Ocean by continental shelf sources of the Antarctic Peninsula

Authors

  • Jeroen de Jong,

    1. Isotopes, Pétrologie, et Environnement, Département des Sciences de la Terre et de l'Environnement, Université Libre de Bruxelles, Brussels, Belgium
    2. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, Texel, Netherlands
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  • Véronique Schoemann,

    1. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, Texel, Netherlands
    2. Laboratoire d'Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium
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  • Delphine Lannuzel,

    1. Laboratoire d'Océanographie Chimique et Géochimie des Eaux, Département des Sciences de la Terre et de l'Environnement, Université Libre de Bruxelles, Brussels, Belgium
    2. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
    3. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia
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  • Peter Croot,

    1. Plymouth Marine Laboratory, Plymouth, UK
    2. Now at Earth and Ocean Sciences, National University of Ireland, Galway, Ireland
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  • Hein de Baar,

    1. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, Texel, Netherlands
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  • Jean-Louis Tison

    1. Laboratoire de Glaciologie, Département des Sciences de la Terre et de l'Environnement, Université Libre de Bruxelles, Brussels, Belgium
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Abstract

[1] In large parts of the Southern Ocean, primary production is limited due to shortage of iron (Fe). We measured vertical Fe profiles in the western Weddell Sea, Weddell-Scotia Confluence, and Antarctic Circumpolar Current (ACC), showing that Fe is derived from benthic Fe diffusion and sediment resuspension in areas characterized by high turbulence due to rugged bottom topography. Our data together with literature data reveal an exponential decrease of dissolved Fe (DFe) concentrations with increasing distance from the continental shelves of the Antarctic Peninsula and the western Weddell Sea. This decrease can be observed 3500 km eastward of the Antarctic Peninsula area, downstream the ACC. We estimated DFe summer fluxes into the upper mixed layer of the Atlantic sector of the Southern Ocean and found that horizontal advection dominates DFe supply, representing 54 ± 15% of the total flux, with significant vertical advection second most important at 29 ± 13%. Horizontal and vertical diffusion are weak with 1 ± 2% and 1 ± 1%, respectively. The atmospheric contribution is insignificant close to the Antarctic continent but increases to 15 ± 10% in the remotest waters (>1500 km offshore) of the ACC. Translating Southern Ocean carbon fixation by primary producers into biogenic Fe fixation shows a twofold excess of new DFe input close to the Antarctic continent and a one-third shortage in the open ocean. Fe recycling, with an estimated “fe” ratio of 0.59, is the likely pathway to balance new DFe supply and Fe fixation.

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