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

Jill Sutton (1) , Gregory F. De Souza (2) , Maribel I. Garcia-Ibiliez (3, 4) , Christina L. de La Rocha (1)

1 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
2 Institute of Geochemistry and Petrology [ETH Zürich]
3 BCCR - Bjerknes Centre for Climate Research
4 CSIC - Consejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain]

The stable isotope composition of dissolved silicon in seawater (delta Si-30(DSi)) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40-60 degrees N) and Labrador Sea. Variations in delta Si-30(DSi) below 500 m were closely tied to the distribution of water masses. Higher delta Si-30(DSi) values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower delta Si-30(DSi) values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest delta Si-30(DSi) 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 delta Si-30(DSi) distribution is marked clearly by Labrador Sea Water (LSW), whose high delta Si-30(DSi) 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 delta Si-30(DSi) and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE delta Si-30(DSi) 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 delta Si-30(DSi) distribution.

Mots clés: ACL; southern-ocean; biogenic silica; marine diatoms; natural-waters; fractionation; labrador sea; hydrography; mediterranean outflow; deep-water masses; eastern equatorial pacific

Domaines: Biodiversité et Ecologie; Océan, Atmosphère

Jill Sutton, Gregory F. De Souza, Maribel I. Garcia-Ibiliez, Christina L. de La Rocha. The silicon stable isotope distribution along the GEOVIDE section (GEOTRACES GA-01) of the North Atlantic Ocean. Biogeosciences, 2018, 15 (18), pp.5663-5676. ⟨10.5194/bg-15-5663-2018⟩. ⟨hal-02651012⟩