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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 18
Biogeosciences, 15, 5663-5676, 2018
https://doi.org/10.5194/bg-15-5663-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: GEOVIDE, an international GEOTRACES study along the OVIDE...

Biogeosciences, 15, 5663-5676, 2018
https://doi.org/10.5194/bg-15-5663-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 21 Sep 2018

Research article | 21 Sep 2018

The silicon stable isotope distribution along the GEOVIDE section (GEOTRACES GA-01) of the North Atlantic Ocean

Jill N. Sutton1, Gregory F. de Souza2, Maribel I. García-Ibáñez3,4, and Christina L. De La Rocha5,a Jill N. Sutton et al.
  • 1Université de Brest, UMR 6539 CNRS/UBO/IRD/Ifremer, LEMAR, IUEM, 29280, Plouzané, France
  • 2ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstrasse 25, 8092 Zurich, Switzerland
  • 3Uni Research Climate, Bjerknes Centre for Climate Research, Bergen 5008, Norway
  • 4Instituto de Investigaciones Marinas, IIM-CSIC, Eduardo Cabello 6, 36208 Vigo, Spain
  • 5independent researcher
  • aformerly at: Université de Brest, UMR 6539 CNRS/UBO/IRD/Ifremer, LEMAR, IUEM, 29280, Plouzané, France

Abstract. The stable isotope composition of dissolved silicon in seawater (δ30SiDSi) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40–60°N) and Labrador Sea. Variations in δ30SiDSi below 500m were closely tied to the distribution of water masses. Higher δ30SiDSi values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower δ30SiDSi values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest δ30SiDSi values were observed in the deep and abyssal eastern North Atlantic, where dense southern-sourced waters dominate. The extent to which the spreading of water masses influences the δ30SiDSi distribution is marked clearly by Labrador Sea Water (LSW), whose high δ30SiDSi signature is visible not only within its region of formation within the Labrador and Irminger seas, but also throughout the mid-depth western and eastern North Atlantic Ocean. Both δ30SiDSi and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE δ30SiDSi distribution thus provides a clear view of the direct interaction between subpolar/polar water masses of northern and southern origin, and allow examination of the extent to which these far-field signals influence the local δ30SiDSi distribution.

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The silicon stable isotope distribution determined from samples collected from the North Atlantic Ocean indicates that water mass subduction and circulation are the dominant processes controlling the distribution of dissolved silicon in this region. In addition, these data provide a clear view of the direct interaction between northern and southern water masses and the extent to which the silicon isotope composition of these silica-poor waters is influenced by hydrography.
The silicon stable isotope distribution determined from samples collected from the North...
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