Cross‐Boundary Heat and Freshwater Transports by Mesoscale Eddies in the Western Subpolar North Atlantic

Abstract The boundary current of the North Atlantic Subpolar Gyre (SPG) is a crucial component of the meridional overturning circulation. Using 18 years (2002–2019) of satellite altimetry and hydrographic profiles, this study provides a comprehensive observational analysis of the role of mesoscale eddies in transporting heat and freshwater across the western boundary of the SPG from the Denmark Strait to Flemish Cap. The eddies are found to predominantly propagate westward across the gyre boundary, transporting water masses with thermohaline properties distinct from those of the adjacent boundary current. When vertically integrated, the eddy‐induced transports yield a net offshore‐bound heat flux of −0.28 ± 0.07 TW and a net onshore‐bound freshwater flux of −0.22 ± 0.05 mSv, respectively, contributing to the cooling and freshening of the boundary current. Distinct regional patterns emerge, with particularly strong offshore heat transport and onshore freshwater transport in the eastern Labrador Sea. These findings improve our understanding of eddy‐driven water mass transformation along the SPG boundary currents and provide context for their potential influence on larger‐scale North Atlantic circulation.