Continental shelves are important sources of iron (Fe) in the land-dominated Arctic Ocean.To understand the export of Fe from the Arctic to Baffin Bay (BB) and the North Atlantic, we studied the alteration of the Fe signature in waters transiting the Canadian Arctic Archipelago (CAA). During its transit through the CAA, inflowing Arctic Waters from the Canada Basin become enriched in Fe as result of strong sediment resuspension and enhanced sediment-water interactions (non-reductive dissolution). These high Fe waters are exported to BB, where approximately 10.7 kt of Fe are delivered yearly from Lancaster Sound. Furthermore, if the two remaining main CAA pathways (Jones Sound and Nares Strait) are included, this shelf environment would be a dominant source term of Fe (dFe + pFe: 26-90 kt y −1 ) to Baffin Bay. The conservative Fe flux estimate (26 kt y −1 ) is 1.7-38 times greater than atmospheric inputs, and may be crucial in supporting primary production and nitrogen fixation in BB and beyond.

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This study addresses an important knowledge gap in the distribution of lead (Pb) in the Arctic Ocean, by presenting dissolved Pb concentrations from samples collected during the GEOTRACES Canadian cruise in 2015. Dissolved Pb showed an increase in concentration from the Canada Basin toward Baffin Bay and the Labrador Sea. Canada Basin was the most isolated region from anthropogenic Pb inputs with low background concentrations (1.4−6.2 pmol kg −1 ) across most of the basin, although higher Pb features from the advection of Pacific-derived waters and sea ice meltwater were present. Likewise, high-Pb peaks (13.5−26.6 pmol kg −1 ) along narrow isopycnal surfaces (σ θ , 27.4−27.6) in Baffin Bay were attributed to the advection of North Atlantic waters spreading a high-Pb signature into the bay, contrasting with the low values (2.5−7.4 pmol kg −1 ) present in the mixed layer, Arctic and Baffin Bay deep waters. The Labrador Sea, largely influenced by the recirculation of North Atlantic waters, had the highest Pb concentrations (∼17−34 pmol kg −1 ) measured in this study. The Canadian Arctic Archipelago (CAA) represents a transition environment influenced by Arctic waters imprinting a low-Pb signature in the western CAA and the southern side of Parry Channel, while Baffin Bay waters prevailed in the eastern CAA recirculating westward along the northern side of Parry Channel and progressively losing their relatively high Pb signature. Extremely low concentrations were measured in Canada Basin and CAA waters, which reflect the remoteness of this region from anthropogenic inputs as well as the old ventilation age of deep waters' masses, providing a baseline for assessing future Pb studies. Finally, we successfully integrate modeling data with field observations demonstrating that dissolved lead, due to its distinctive anthropogenic signature in North Atlantic waters, can be a useful complementary tracer of water masses in the Canadian Arctic Ocean.

Biogeochemical cycles in the Arctic Ocean are sensitive to the transport of materials from continental shelves into central basins by sea ice. However, it is difficult to assess the net effect of this supply mechanism due to the spatial heterogeneity of sea ice content. Manganese (Mn) is a micronutrient and tracer which integrates source fluctuations in space and time while retaining seasonal variability. The Arctic Ocean surface Mn maximum is attributed to freshwater, but studies struggle to distinguish sea ice and river contributions. Informed by observations from 2009 IPY and 2015 Canadian GEOTRACES cruises, we developed a three‐dimensional dissolved Mn model within a 1/12° coupled ocean‐ice model centered on the Canada Basin and the Canadian Arctic Archipelago (CAA). Simulations from 2002 to 2019 indicate that annually, 87%–93% of Mn contributed to the Canada Basin upper ocean is released by sea ice, while rivers, although locally significant, contribute only 2.2%–8.5%. Downstream, sea ice provides 34% of Mn transported from Parry Channel into Baffin Bay. While rivers are often considered the main source of Mn, our findings suggest that in the Canada Basin they are less important than sea ice. However, within the shelf‐dominated CAA, both rivers and sediment resuspension are important. Climate‐induced disruption of the transpolar drift may reduce the Canada Basin Mn maximum and supply downstream. Other micronutrients found in sediments, such as Fe, may be similarly affected. These results highlight the vulnerability of the biogeochemical supply mechanisms in the Arctic Ocean and the subpolar seas to climatic changes.

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