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The vertical distribution of iron stable isotopes in the North Atlantic near Bermuda

John, Seth G. and Adkins, Jess (2012) The vertical distribution of iron stable isotopes in the North Atlantic near Bermuda. Global Biogeochemical Cycles, 26 . Art. No. GB2034. ISSN 0886-6236.

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Seawater dissolved iron isotope ratios (δ^(56)Fe) have been measured in the North Atlantic near Bermuda. In a full-depth profile, seawater dissolved δ^(56)Fe is isotopically heavy compared to crustal values throughout the water column (δ^(56)Fe_(IRMM-014) = +0.30‰ to +0.71‰). Iron isotope ratios are relatively homogenous in the upper water column (between +0.30‰ to +0.45‰ above 1500 m), and δ^(56)Fe increases below this to a maximum of +0.71‰ at 2500 m, decreasing again to +0.35‰ at 4200 m. The δ^(56)Fe profile is very different from the iron concentration profile; in the upper water column [Fe] is variable while δ^(56)Fe is relatively constant, and in the deeper water column δ^(56)Fe varies while [Fe] remains relatively constant. The δ^(56)Fe profile is also not well correlated with other hydrographic tracers in the North Atlantic such as temperature, salinity, or the concentrations of oxygen, phosphate, silica, and CFC-11. The dissimilarity between δ^(56)Fe profiles and profiles of [Fe] and other hydrographic tracers shows that Fe isotope ratios provide a unique sort of information about ocean chemistry, and they suggest that Fe isotopes may therefore be a valuable new tool for tracing the global sources, sinks, and biogeochemical cycling of Fe.

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Adkins, Jess0000-0002-3174-5190
Additional Information:© 2012 American Geophysical Union. Received 27 January 2011; accepted 2 May 2012; published 15 June 2012. Thanks to all who helped and participated on the Geotraces Intercalibration I cruise, especially Chief Scientist Greg Cutter, Ed Boyle, Geoffrey Smith, and the captain and crew of the R/V Knorr.
Subject Keywords:iron; isotopes; marine; seawater
Record Number:CaltechAUTHORS:20120711-132003222
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Official Citation:John, S. G. and J. Adkins (2012), The vertical distribution of iron stable isotopes in the North Atlantic near Bermuda, Global Biogeochem. Cycles, 26, GB2034, doi:10.1029/2011GB004043.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32361
Deposited By: Jason Perez
Deposited On:11 Jul 2012 20:55
Last Modified:24 Feb 2020 10:30

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