Seawater dissolved samples were taken from the US GEOTRACES trace-metal clean rosette, or underway towfish system.\u00a0
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Methods for Fe, Zn, and Cd stable isotope and concentration analyses have been described in detail in previous manuscripts (Conway et al., 2016, 2013; Conway & John, 2014a, 2014b; T.M. Conway & John, 2015; Tim M Conway & John, 2015; John et al., 2018a, 2018b)). Briefly:
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Concentration measurements were made using an offline adaptation of the seaFAST-pico metal extraction system (Elemental Scientific Inc.) as described in Lagerstrom et al. (2013). Briefly, using the seaFAST, 10 mL aliquots of seawater were extracted onto Nobias PA1 chelating resin at pH ~ 6.5 with an ammonium acetate/acetic acid buffer, then eluted in 10% v/v nitric acid (HNO3). Metal concentrations were measured on a Thermo Fisher Element 2 HR-ICP-MS.
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Fe, Zn, Cd, Ni, Cu, and Pb concentrations were measured by isotope dilution. Recoveries for Ni were used to adjust the final concentrations of Mn and REEs.
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The accuracy of our analytical procedure was verified by analysis of a seawater reference material (GEOTRACES 2008 GS), for which good agreement with the reported consensus values were obtained.
Concentrations and stable isotope ratios of Fe, Zn, and Cd from the US GEOTRACES Arctic cruise GN01 (HLY1502) from August to October 2015. A subset of these data has been published in Zhang et al., 2019.