Southern Ocean control of silicon stable isotope distribution in the deep Atlantic Ocean
Table S1: Hydrographic parameters, nutrient concentrations, δ30Si values, and parameters related to the endmember contribution calculation for all samples. (6.361Kb)
Table S1: Hydrographic parameters, nutrient concentrations, δ30Si values, and parameters related to the endmember contribution calculation for all samples. (51Kb)
de Souza, Gregory F.
Reynolds, Ben C.
Saito, Mak A.
Gerringa, Loes J. A.
MetadataShow full item record
The fractionation of silicon (Si) stable isotopes by biological activity in the surface ocean makes the stable isotope composition of silicon (δ30Si) dissolved in seawater a sensitive tracer of the oceanic biogeochemical Si cycle. We present a high-precision dataset that characterizes the δ30Si distribution in the deep Atlantic Ocean from Denmark Strait to Drake Passage, documenting strong meridional and smaller, but resolvable, vertical δ30Si gradients. We show that these gradients are related to the two sources of deep and bottom waters in the Atlantic Ocean: waters of North Atlantic and Nordic origin carry a high δ30Si signature of ≥+1.7‰ into the deep Atlantic, while Antarctic Bottom Water transports Si with a low δ30Si value of around +1.2‰. The deep Atlantic δ30Si distribution is thus governed by the quasi-conservative mixing of Si from these two isotopically distinct sources. This disparity in Si isotope composition between the North Atlantic and Southern Ocean is in marked contrast to the homogeneity of the stable nitrogen isotope composition of deep ocean nitrate (δ15N-NO3). We infer that the meridional δ30Si gradient derives from the transport of the high δ30Si signature of Southern Ocean intermediate/mode waters into the North Atlantic by the upper return path of the meridional overturning circulation (MOC). The basin-scale deep Atlantic δ30Si gradient thus owes its existence to the interaction of the physical circulation with biological nutrient uptake at high southern latitudes, which fractionates Si isotopes between the abyssal and intermediate/mode waters formed in the Southern Ocean.
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Geochemical Cycles 26 (2012): GB2035, doi:10.1029/2011GB004141.
Showing items related by title, author, creator and subject.
Diatom silicon isotopes as a proxy for silicic acid utilisation : a Southern Ocean core top calibration Egan, Katherine E.; Rickaby, Rosalind E. M.; Leng, Melanie J.; Hendry, Katharine R.; Hermoso, Michael; Sloane, Hilary J.; Bostock, Helen; Halliday, Alex N. (Elsevier, 2012-08-11)Despite a growing body of work that uses diatom δ30Si to reconstruct past changes in silicic acid utilisation, few studies have focused on calibrating core top data with modern oceanographic conditions. In this study, a ...
Silicon isotopes indicate enhanced carbon export efficiency in the North Atlantic during deglaciation Hendry, Katharine R.; Robinson, Laura F.; McManus, Jerry F.; Hays, James D. (2013-11-11)Today's Sargasso Sea is nutrient-starved, except for episodic upwelling events caused by wind-driven winter mixing and eddies. Enhanced diatom opal burial in Sargasso Sea sediments indicates that silicic acid, a limiting ...
Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions Hendry, Katharine R.; Georg, R. Bastian; Rickaby, Rosalind E. M.; Robinson, Laura F.; Halliday, Alex N. (2010-02)The relative importance of biological and physical processes within the Southern Ocean for the storage of carbon and atmospheric pCO2 on glacial-interglacial timescales remains uncertain. Understanding the impact of ...