The Transformation of Trace Metal Distributions Across the Mackenzie Shelf and Through the Northwest Passage

Understanding the distributions of trace elements, like iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), barium (Ba), and vanadium (V) in the Arctic Ocean is motivated in part because they can modulate key biogeochemical rate processes as micronutrients and/or toxins for primary producers, and can serve as water‐mass tracers, revealing modification of Atlantic and Pacific endmembers during Arctic transit. Dissolved trace metal concentrations were measured in seawater in 2021 from the shelf of the Mackenzie River Delta and through the Northwest Passage of the Canadian Arctic Archipelago (CAA). A four‐dimensional linear mixing model, using salinity, Ba concentrations, and Arctic nitrate‐phosphate (ANP) endmembers, was applied to determine water mass distributions. This approach identifies sources and sinks of trace metals as waters move from the western Arctic through the Northwest Passage toward Baffin Bay, with implications for Arctic ecosystems and the properties of waters exported to the North Atlantic. Nutrient‐rich Pacific waters entering the western Arctic are modified by sedimentary inputs with transit over the Chukchi shelf. In particular, elevated Cd and Zn in upper halocline waters extend from the Chukchi shelf into the coastal Beaufort Sea, Mackenzie shelf, and Amundsen Gulf. During transit, waters are further modified by inputs from the Mackenzie River (Mn, Co, Ni, Cu), sea ice melt (Mn, Co, Fe, Cu), sediment resuspension on the Mackenzie Shelf (Fe, Pb) and riverine Cu inputs within the CAA.