Abstract
The general surface circulation of the Nordic Seas consists of poleward flowing relatively warm waters from the Atlantic and a return flow along the East Greenland Current with colder and fresher waters, along with transformed Atlantic waters sub-surface. The mid-depth circulation of the Nordic Seas, particularly the exchange between the various basins, however, has not been well studied, but is important for understanding the main pathways between dense water formation regions towards the overflows of the Greenland Scotland Ridge. The transformation of the water to denser and colder waters is important for dense water overflowing towards the North Atlantic and supplying the lower limb of the AMOC. Here we use Argo floats drifting at intermediate depths (1000 – 1500 m) to provide an overview of this mid-depth circulation. We found the highest velocities along the boundaries and in the Norwegian Sea along steep topography, while the velocities in the interior basins are lower. Floats generally remain within the basin they were deployed in unless they are entrained into the boundary current. This occurs primarily when the interior gyre circulation is close to the boundary, or where steep topography can cause instabilities. The exchanges across submarine ridges show certain preferred inter-basin pathways, except for the crossings between the Greenland and Lofoten Seas. This circulation shows similar features to the surface boundary current, but interior pathways are distinctly different and reveal the main pathways connecting the basins.