Assessing North Sea carbon and nutrient cycle responses to regional and global climate change

The North Sea is a very productive and heavily exploited continental shelf sea that absorbs considerable quantities of atmospheric CO₂. The fraction of absorbed CO₂ 1) flowing out towards the North Atlantic and 2) buried in sediments, is highly uncertain, rendering future changes of the system difficult to predict. As part of the NoSE (North Sea-Atlantic Exchange) project, this study focuses on the present-day and future roles of the North Sea within the wider carbon and biogeochemical systems of the Atlantic Ocean. Specifically, in this study we will assess the response of carbon and nutrient cycling in the North Sea and the adjacent North Atlantic Ocean to regional and global climate change.

            The carbon cycle configuration of state-of-the-art Earth System Model EC-Earth3, EC-Earth3-CC (atmosphere: IFS36r4; land surface: HTESSEL; Ocean: NEMO3.6; Sea ice: LIM3; Dynamic vegetation: LPJ-GUESS; Atmospheric composition: TM5; Ocean biogeochemistry: PISCES) was used to simulate both present-day (1981 – 2020) and future (2071 – 2100) climate, marine biogeochemistry, ocean primary production and nutrient distributions. Here, we present a validation of the EC-Earth3-CC present-day climatologies in the North Sea and adjacent parts of the North Atlantic Ocean, using existing observational datasets. We also compare the EC-Earth3-CC results to other global (CMIP6) and regional climate models to infer how EC-Earth3-CC biases compare to deficiencies in other models. Furthermore, we will address the response of the North Sea carbon and nutrient fluxes and budgets to regional and global climate change by comparing the present-day and future climatologies.

            This study will reveal new insights into the cycling of carbon and nutrients in the North Sea, their exchange with the Atlantic Ocean, and how these processes may evolve in the future.