Global simulations of ocean-sea ice-biogeochemistry model FESOM2.1-REcoM3 with eddy-permitting grid resolution and terrigenous inputs in the Arctic Ocean

Project: Towards a better understanding of the nutrient cycles in the ‘new’ Arctic Ocean and implications for future primary productivity and carbon export - The Arctic is warming more than twice as fast as temperate regions due to anthropogenic Climate Change, and summer sea-ice is expected to vanish by the middle of the century. In this context, we hypothesize that Arctic marine primary productivity will increase due to sea-ice loss until the limitation of nutrients (nitrate in particular) outweighs the benefits of higher light availability. The available upper ocean “nutrient stocks” that get replenished in winter determine to a large extent the annual primary production. However, the quantity of nutrients remineralized in the Arctic Ocean is unknown, leading to an unbalanced budget - i.e. a ‘missing source’ of nitrate remains to be discovered. This glaring gap in our understanding is mainly due to the extreme scarcity of nutrient data, especially during the ‘polar night’ in winter and from the mesopelagic ‘twilight zone’ (in ~100-1000 m depth). The objective of the nuArctic project is to address this knowledge gap by testing the hypothesis that terrigenous inputs drive key feedbacks in the Arctic Ocean's carbon and nutrient cycles—primarily through the remineralization of organic matter, a critical process linking surface and deep ocean layers.

nuArctic has been funded by the BMBF (project 03F0918A). Computing resources were provided by the North-German Supercomputing Alliance (HLRN) project hbk00083. This work has also received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 820989 (project COMFORT; https://comfort.w.uib.no/). COMFORT aims to assess tipping points in the coupled cycles of carbon, oxygen, and nutrients in the ocean for determining and achieving safe operating spaces.
Summary: nuArctic aims at increasing our understanding of the remineralization of nutrients and carbon in the Arctic Ocean and its feedbacks with the Earth System, i.e. the capacity of the Arctic Ocean to be productive and to act as a carbon sink into the future. To do so, the project is proposing modeling advances to increase the robustness of model projections. This project includes global model simulations with the global multi-resolution Finite Volume Sea Ice-Ocean Model (FESOM version 2.1) coupled to the Regulated Ecosystem Model (REcoM version 3, Gürses et al. 2024). For this project, model simulations include a representation of terrigenous inputs from both rivers and coastal erosion and were run from 1970-2100 on a model grid with eddy-permitting (4.5 km) resolution at pan-Arctic scale. The ocean-only model simulations were forced at the ocean surface with 3-hourly atmospheric output from the AWI Climate Model (Semmler et al. 2020). The project includes model experiments under four “Shared Socioeconomic Pathways” emission scenarios, a control run and sensitivity experiments. This work lead to the publication of Oziel et al. 2025 ("Climate change and terrigenous inputs decrease the efficiency of the future Arctic Ocean’s biological carbon pump » in 2025 in Nature Climate Change) which comprises a detailed description of the methods, model experiments and setups but also a publication of the source code and post-processing scripts (Oziel, 2024).