LAUSR

Abstract Downscaling simulations for emission scenario RCP8.5 with a regionally coupled ocean-atmosphere climate system model indicate a regime shift in the dynamics of Atlantic nutrient supply to the Northwest European Shelf. Reduced winter convection in the Northeast Atlantic leads to a substantial decrease in upper ocean nutrient concentrations. Yet, vertical mixing processes at the shelf break maintain a connection to nutrient-enriched subpycnocline water masses and decouple the nutrient supply to the shelf from upper ocean conditions in the North Atlantic. As a consequence, primary production on the shelf does not weaken as strongly as it was expected from declining nutrient concentrations in the open ocean. Furthermore, nutrient fluxes to the shelf become increasingly variable due to a positive feedback between the winter mixed layer depth near the shelf break and the density of the upper water column, making the productivity on the shelf more sensitive to the major modes of variability in the North Atlantic.