The Faroe Bank Channel Overflow (FBCO) supplies the densest and deepest limb of the Atlantic Meridional Overturning Circulation, which helps regulate Earth’s climate. Despite long-term monitoring of the FBCO, many aspects regarding the upstream sources and pathways of this dense water remain unclear. To advance our understanding of this, we analyze a composite high-resolution hydrographic and velocity dataset from four shipboard surveys conducted between August and October 2024, spanning the region from the Faroe Bank Channel northward to the Iceland and Greenland Seas. The quantification of overflow water transport reveals two major upstream pathways: one following the Mohn and Jan Mayen Ridges southward through the interior Nordic Seas, and another originating from the western boundary current system, crossing the Spar Fracture Zone on the northern Iceland slope and feeding the Iceland–Faroe Slope Jet. Estimates of surface water mass transformation using historical observations and reanalysis products suggest that the densest portion of the FBCO is produced in the Greenland Sea, whereas less dense overflow water is transformed along the boundary current system surrounding the Nordic Seas. Lagrangian particle-release experiments further indicate that dense water originating from the boundary current system supplies the pathway crossing the Spar Fracture Zone, while dense water produced in the Greenland Sea mainly feeds the pathways in the interior of the Nordic Seas. These results provide an updated view of the upstream sources, transformation regions, and advective pathways feeding the FBCO.

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