Shelf–Fjord Exchange Regulated by Recirculating Greenland Meltwater in Glacial Troughs

The Greenland Ice Sheet is rapidly losing mass due to climate warming, contributing significantly to global sea level rise and altering ocean circulation and ecosystems. Yet, the processes controlling interactions between glacial fjords and the adjacent continental shelf and slope are not fully understood, particularly the role of bathymetric troughs in modulating water exchange between the fjords and boundary current system. Here we present high-resolution shipboard, reanalysis, and numerical model data across several deep troughs in West Greenland, revealing a recurring anticyclonic recirculation of glacial meltwater within the inner Uummannaq trough, which isolates the glacial fjord from subsurface Atlantic Water inflow and thus limits oceanic heat penetration. This circulation—driven by seasonal meltwater discharge and modulated by wind forcing—contrasts with the adjacent Jakobshavn trough, where more efficient exchange prevents such retention. The presence of recirculating freshwater correlates with enhanced nutrient concentrations and isotopic signatures, suggesting broader biogeochemical impacts. Analogous recirculation patterns are also present in some East Greenland fjords where ice loss has been comparatively reduced. Our findings emphasize the critical role of fjord-shelf topography and regional dynamics in modulating Greenland’s glacial melting, freshwater export, and nutrient delivery, highlighting the need for improved representation of these processes in climate models.