Both soluble and colloidal iron phases control dissolved iron variability in the tropical North Atlantic Ocean

• Main Authors: Jessica N Fitzsimmons, Edward A Boyle
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Mid-Atlantic Ridge; Antarc*; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1048.1850; http://boyle.mit.edu/%7Eed/pdfs/Fitzsimmons%282013%29GCA_125_539.pdf

Abstract The size partitioning of dissolved iron (dFe, <0.4 lm) into soluble (sFe, <0.02 lm) and colloidal (0.02 lm < cFe < 0.4 lm) phases was investigated at seven stations in the tropical North Atlantic Ocean, and the results are compared to the dFe size fractionation study of [sFe] = 0.42 ± 0.03 nmol/kg) and in the oxygen minimum zone (56% sFe; [sFe] = 0.65 ± 0.03 nmol/kg). Only at remineralization depths of stations with intermediate oxygen concentrations (100-110 lmol/kg) did colloidal Fe dominate (contributing 58% of dFe) , indicating that cFe may be serving as a conduit of dFe loss during mixing of high-Fe OMZ and low-Fe gyre waters. North Atlantic Deep Water (NADW) had a typical sFe concentration of 0.34 ± 0.05 nmol/kg. In the deepest samples composed of a NADW/Antarctic Bottom Water mixture where the bottom water may have attained a $0.1 nmol/kg hydrothermal Fe input during transit past the Mid-Atlantic Ridge, sFe did not increase coincidentally with dFe, indicating that any potential hydrothermal Fe contribution was colloidal. In general, the results of this study counter the previous hypothesis of