Trace element concentrations in the water column of the Canadian Arctic Ocean measured from the CCGS Amundsen in 2009, 2019, 2021, 2022 and 2024

Trace metals in the ocean, including iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb) and vanadium (V), may act as micronutrients or toxins to marine phytoplankton and thereby directly impact primary productivity. In the western Canadian Arctic, the chemical composition of Pacific- and Atlantic-derived waters are modified during transport over the Mackenzie shelf and through the Northwest Passage. Remineralization in sediments on the Chukchi shelf enriches the concentrations of dissolved Cd and Zn – a signature that can be detected in open waters of the Beaufort Sea as well as the Amundsen Gulf. Over the Mackenzie shelf, sediment resuspension acts as a source of Fe and Pb, and the Mackenzie River plume additionally provides high concentrations of most trace metals; however, this does not translate to effective trace metal transport to the Beaufort Sea’s interior. Through the Canadian Arctic Archipelago (CAA), other sources including small rivers, sea ice, and snow are found to supply trace metals to surface waters, further modifying trace metal concentrations as water is transported eastward. Waters entering the eastern Canadian Arctic via Nares Strait and Parry Channel are found to retain the Chukchi shelf signature of Zn, Cd, and Ni, while these enhanced concentrations dissipate over shallow passages prior to entering Baffin Bay. Other trace metal sources in this eastern corridor include glacial meltwater, particularly in Nares Strait and the North Water Polynya immediately south of this passage, while sea ice melt and meteoric water runoff are found to have less significance relative to the western CAA. Estimates of trace metal flux indicate greatest transport of trace metals into Baffin Bay from Nares Strait, followed by the West Greenland Current in eastern Davis Strait, and finally Lancaster Sound. Flux estimates through Davis Strait indicate the Canadian Arctic is a source of Mn, Co, Ni, Cu, Zn, Cd, Pb, Ba and V to the Atlantic, while Fe export via the Baffin Current is equivalent to Fe import via the West Greenland Current.