Properties and Effects of Mesoscale Eddies in the Eurasian Basin of the Arctic from a Model Simulation at 1-km Resolution

Mesoscale eddies are widespread in the Arctic Ocean affecting circulation, stratification, the transport of heat and salt, and consequently sea ice melt. We detect and track coherent eddies in a 1-km resolution Arctic Ocean simulation using the unstructured-mesh Finite volumE Sea ice-Ocean Model (FESOM2). Their spatial and seasonal distributions are analyzed, and quasi-3D eddy composites are used to quantify their influence on the water column, surface heat fluxes, and sea ice.

Eddy formation is highest along topographic features and the boundary current, with eddy sizes roughly corresponding to the local Rossby radius. Anticyclonic eddies are larger and more energetic than cyclonic eddies and can lift warm, saline Atlantic Water toward the surface, which increases the vertical heat flux and can cause localized basal sea ice melt. Cyclonic eddies, by contrast, mainly transport cold surface water downward and have little impact on the surface heat budget or sea ice. Edd-induced anomalies are strongest in Fram Strait, weaken downstream, and are larger beneath pack ice than in the marginal ice zone. These results are consistent with an eddy-ice pumping mechanism, where ocean-sea ice stress enhances vertical transport and contributes to eddy decay. Overall, the analysis shows that mesoscale eddies play an important role in the vertical exchange of heat in the Eurasian Arctic making them an important factor in the ongoing Atlantification of the Arctic Ocean. Since the role of eddies is expected to become even more important in the future, adequately representing them in model simulations will be necessary, despite the high resolution and computational cost required to resolve them.