Trace Metal Biogeochemistry in the Nordic Seas: Arctic and Atlantic Water Inflows Determine (Micro)Nutrient Availability

Abstract

We present a data set of macronutrient and dissolved and total dissolvable trace metal concentrations collected in June 2012 across the Nordic Seas. Surface water and depth profiles of manganese, iron, cobalt, nickel, copper, zinc, phosphate, silicic acid, and NOx (nitrate + nitrite) reveal how warm saline Atlantic waters and cold fresh Arctic waters shape regional (micro)nutrient availability and phytoplankton growth conditions. At the surface, Arctic waters, depleted in NOx (3.44 ± 3.30 μM) but enriched in Si(OH)₄ (2.15 ± 1.42 μM) and dissolved trace metals (e.g., up to 1.03 nM dFe during peak to post-bloom), reach the western Nordic Seas via the Transpolar Drift and East Greenland Current. Conversely, the North Atlantic Current transports waters enriched in NOx (up to 10.7 μM) to the surface high-latitude North Atlantic (HLNA) and eastern Nordic Seas. These contrasting inputs create distinct nutrient-deficiency regimes: The western Nordic Seas were N deficient, whereas the HLNA and eastern Nordic Seas showed Fe deficiency following the spring bloom. Benthic flux and internal cycling processes, including remineralization and scavenging, further shape (micro)nutrient distributions in the deep waters, in addition to their pre-formed supply in water mass formation regions. The (micro)nutrient fluxes across the Greenland-Scotland Ridge, combined with reported estimates from the Fram Strait and Barents Sea Opening, highlight the Nordic Seas as a transitional region in mediating (micro)nutrient exchange between the Arctic Ocean and HLNA. Future changes in Arctic export may alter elemental stoichiometry in the Nordic Seas, with implications for primary production and biogeochemical cycling.