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Abstract The iodine to calcium ratio in carbonate (I/Ca) has been widely used to indicate ocean oxygenation level in the past. Given the volatility of iodine, I/Ca has been measured in alkaline solutions in previous studies. However, this limits the application of I/Ca with other element/Ca (El/Ca) proxies at the same time and in the same foraminifera because other El/Ca data are preferably analyzed in acidic solutions. This study assesses the reliability of I/Ca measurements in acidic solutions measured with other El/Ca as well as the effects of different sample pre‐treatments on measured foraminiferal I/Ca. Our results show that when samples are measured within hours of prepaparation, the pH of the final solution has an insignificant effect on I/Ca measurements of a carbonate reference material JCp‐1 and a multi‐element standard solution, consistent with the slow kinetics of iodine volatilization. We find, however, that low pH possibly reduces the measured I/Ca in foraminiferal tests in some samples. Our experiments also suggest a resolvable effect of reductive cleaning, yielding lower foraminiferal I/Ca compared to without reductive cleaning. The HNO₃concentration used to dissolve foraminiferal shells has a negligible effect. Despite the different solution pHs and cleaning and dissolving methods, our core top planktic I/Ca data are able to differentiate well‐oxygenated from oxygen‐depleted waters in the upper ocean, and after correcting for cleaning effect, our data are generally consistent with the published studies that analyzed I/Ca without reductive cleaning and in basic solutions. This study shows that measurements of I/Ca within hours of sample dissolutions yield reliable planktic I/Ca data, while also allowing the acquisition of other El/Ca values for paleoceanographic studies. 

Abstract The biogeochemical cycling of dissolved zinc (dZn) was investigated in the Western Arctic along the U.S. GEOTRACES GN01 section. Vertical profiles of dZn in the Arctic are strikingly different than the classic “nutrient‐type” profile commonly seen in the Atlantic and Pacific Oceans, instead exhibiting higher surface concentrations (~1.1 nmol/kg), a shallow subsurface absolute maximum (~4–6 nmol/kg) at 200 m coincident with a macronutrient maximum, and low deep water concentrations (~1.3 nmol/kg) that are homogeneous (sp.) with depth. In contrast to other ocean basins, typical inputs such as rivers, atmospheric inputs, and especially deep remineralization are insignificant in the Arctic. Instead, we demonstrate that dZn distributions in the Arctic are controlled primarily by (1) shelf fluxes following the sediment remineralization of high Zn:C and Zn:Si cells and the seaward advection of those fluxes and (2) mixing of dZn from source waters such as the Atlantic and Pacific Oceans rather than vertical biological regeneration of dZn. This results in both the unique profile shapes and the largely decoupled relationship between dZn and Si found in the Arctic. We found a weak dZn:Si regression in the full water column (0.077 nmol/μmol,r² = 0.58) that is higher than the global slope (0.059 nmol/μmol,r² = 0.94) because of the shelf‐derived halocline dZn enrichments. We hypothesize that the decoupling of Zn:Si in Western Arctic deep waters results primarily from a past ventilation event with unique preformed Zn:Si stoichiometries.