Premium
The vertical distribution of iron stable isotopes in the North Atlantic near Bermuda
Author(s) -
John Seth G.,
Adkins Jess
Publication year - 2012
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2011gb004043
Subject(s) - seawater , water column , biogeochemical cycle , hydrography , oceanography , isotope , water mass , salinity , environmental chemistry , geology , stable isotope ratio , scavenging , chemistry , biochemistry , physics , quantum mechanics , antioxidant
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.