Iron Isotope Biogeochemical Cycling in the Western Arctic Ocean
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AbstractThe Arctic Ocean is unique, connecting the Atlantic and Pacific basins and being especially vulnerable to the impacts of a changing climate. Iron stable isotopes (56Fe) provide a unique window into the biogeochemical cycling of Fe in the Arctic. Here we present the first seawater 56Fe for the Western Arctic Ocean, from the 2015 U.S. GEOTRACES GN01 transect. Samples analyzed for 56Fe include seawater dissolved (<0.2m), soluble (<0.003m), and leachable particulate phases. Several key processes were explored using Fe isotopes, each characterized by a distinct combination of 56Fe and Fe concentrations. Input of Fe from reducing continental shelf sediments was characterized by high dissolved Fe concentrations (6.184.84nmol kg1) and low 56Fe (1.570.66). Riverine Fe input observed in the Transpolar Drift Current was characterized by high Fe concentrations corresponding to a riverine endmember Fe concentration of 19nM, and nearzero 56Fe (0.020.23) that was similar to that of average crustal material. The deep Arctic was mostly characterized by low Fe concentrations (0.330.14nmol kg1) and slightly higher 56Fe (0.050.30), except for samples taken near continental slopes that were affected by sedimentary Fe input with lower 56Fe, and in the Amundsen Basin which showed possible hydrothermal Fe input. Our data thus illuminate Fe biogeochemical cycling processes in the modern Arctic Ocean, and serve as a baseline for understanding how the Arctic Fe cycle responds to climate change.
