Dissolved Cd, Co, Cu, Fe, Mn, Ni, and Zn in the Arctic Ocean

• Published in: Journal of geophysical research. Oceans 2021-09, Vol.126 (9), p.n/a
• Main Authors: Gerringa, L. J. A., Rijkenberg, M. J. A., Slagter, H. A., Laan, P., Paffrath, R., Bauch, D., Rutgers van der Loeff, M., Middag, R.
• Format: Article
• Language: English
• Subjects: Arctic Ocean; Basins; Biological activity; Cadmium; Climate change; Cobalt; Continental slope; Convection; Copper; Deep water; dissolved metals; Drift; Expeditions; Geophysics; GEOTRACES; Heavy metals; Icebreakers; Iron; Manganese; Metal concentrations; Metals; Nickel; Nutrients; Oceans; Organic matter; Particulate flux; Residence time; Residence time distribution; River water; Rivers; Scavenging; Silicates; Surface water; Temperature rise; Trace metals; Water discharge; Zinc
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2021JC017323

During the Polarstern (PS94) expedition, summer 2015, part of the international GEOTRACES program, sources and sinks of dissolved (D) Cd, Co, Cu, Fe, Mn, Ni, and Zn were studied in the central Arctic Ocean. In the Polar Surface Water in which the TransPolar Drift (TPD) is situated, salinity and δ18O derived fractions indicated a distinct riverine source for silicate DCo, DCu, DFe, DMn, and DNi. Linear relationships between DMn and the meteoric fraction depended on source distance, likely due to Mn‐precipitation during transport. In the upper 50 m of the Makarov Basin, outside the TPD core, DCo, DMn, DNi, DCd, and DCu were enriched by Pacific waters, whereas DFe seemed diluted. DCo, DFe, DMn, and DZn were relatively high in the Barents Sea and led to enrichment of Atlantic water flowing into the Nansen Basin. Deep concentrations of all metals were significantly lower in the Makarov Basin compared to the Nansen and Amundsen, the Eurasian, Basins. The Gakkel ridge hydrothermal input and higher continental slope convection are explanations for higher metal concentrations in the Eurasian Basins. Although scavenging rates are lower in the Makarov Basin compared to the Eurasian Basins, the residence time is longer and therefore scavenging can decrease the dissolved concentrations with time. This study provides a baseline to assess future change, and additionally identifies processes driving trace metal distributions. Our results underline the importance of fluvial input as well as shelf sources and internal cycling, notably scavenging, for the distribution of bio‐active metals in the Arctic Ocean. Plain Language Summary Of the oceans on our planet, the Arctic Ocean is subject to the most rapid climate change. The temperature rise, increases the discharge of Arctic river water, rich in nutrients, dissolved metals and organic matter. The transpolar drift (TPD), transports this water over the Arctic Ocean toward the Atlantic Ocean. In the present study we describe the dissolved concentrations of biologically active trace metals cadmium, cobalt, copper, iron, manganese, nickel, and zinc in the central Arctic Ocean during an expedition with the ice breaker Polarstern. Our results showed that rivers bring iron, cobalt, copper, iron, manganese, nickel into the Arctic Ocean, transported further by the TPD. In the deep waters, deeper than 1,500–2,000 m, there is a significant difference in the concentrations of all metals between the Eurasian and the American–Canadian sid