Resolving Shelf Break Exchange Around the European Northwest Shelf

Shelf seas act as a significant sink of carbon within the global ocean. This occurs as carbon is exported beneath the permanent oceanic thermocline through the downwelling circulation across the shelf break. This downwelling circulation is quantified here using two regional ocean model configurations of the European northwest shelf, with differing resolution (7- and 1.5-km grid spacing). The dominant mechanisms and impact of model resolution are assessed along the length of the shelf break. The total downwelling circulation is stronger at higher resolution, due to an increased on-shelf transport at internal depths (20–150 m) and increased off-shelf transport at the base of the water column. At internal depths, these differences increase seasonally, influenced by stratification. Key processes in cross-shelf exchange only begin to be resolved at O(1 km), implying that global models currently used to assess the carbon cycles will be missing these processes.