A Multi-Decade Tracer Study of the Circulation and Spreading Rates of Atlantic Water in the Arctic Ocean

In this contribution, we present tritium-3He (3H-3He) apparent ages and hydrographic data from 21 expeditions spanning 27 years of Arctic Ocean section work (1987-2013) to estimate flow paths and spreading velocities of the Atlantic Waters (AW) circulation on a pan-Arctic scale. Tracer data not only corroborate the well-organized cyclonic flow along the continental slope but also introduce a temporal dimension to these observations. Additionally, they provide insights into other circulation branches of the Atlantic layer, which are hypothesized to be influenced by deep submarine ridges. Tracer measurements indicate that mean spreading rates vary across different branches of the circulation pattern. Along the boundary current, spreading velocities range from approximately 0.7 to 1.5 cm s-1, with no significant difference observed between the waters of the two vertically stacked Atlantic branches. Within the limits of our method, tracer data support the hypothesis originally proposed by Rudels et al. (1994), -of stable pathways in the Atlantic Layer, influenced by topographic constraints.