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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 (similar to 1.1 nmol/kg), a shallow subsurface absolute maximum (similar to 4-6 nmol/kg) at 200 m coincident with a macronutrient maximum, and low deep water concentrations (similar to 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/mu mol, r(2) = 0.58) that is higher than the global slope (0.059 nmol/mu mol, r(2) = 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.

Plain Language Summary The Arctic Ocean is an understudied ocean basin that is already experiencing rapid changes as a result of climate change. Understanding nutrient sources and sinks in the Arctic is critical to predicting how the nutrient supply to Arctic organisms might change upon future climate change. Zinc is a micronutrient that, while not limiting to most photosynthesizing ocean plankton, does play a role in modulating the community composition of these primary producers. We measured dissolved zinc distributions in the Western Arctic Ocean for the first time and found them to be strikingly different from the classic "nutrient-type" profile of other ocean basins. Only over the shallow continental margin did biological zinc cycling dominate its distribution; otherwise, zinc was determined mostly by mixing between Atlantic and Pacific incoming waters, without biological overprinting. Additionally, the largest zinc source was from the regeneration of zinc-rich cells in sediment porewaters over the Chukchi shelf, and this zinc was transported far offshore in the Arctic halocline. Surprisingly, typical zinc sources such as rivers, atmospheric inputs, and especially deep regeneration were insignificant in the Arctic.