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 fill this gap by assimilating data from the MOSAiC drift expedition into a ‘state-of-the-art’ biogeochemical model, implemented as well in an Earth System Model (ESM). nuArctic will investigate the remineralization of organic matter, a pivotal process that connects the near surface and the deeper ocean. Remineralization modulates the biogeochemical cycling of key ecological substances such as nutrients, oxygen and carbon. In particular, nuArctic will increase the understanding of the remineralization of nutrients and its feedbacks with the ecosystem functioning (i.e annual primary production, planktonic assemblage composition). Our advances in the modelling of remineralization will (1) produce a pan-Arctic nutrient and carbon budget for the last 4 decades and (2) increase the robustness of projections of the Arctic Ocean’s primary productivity and ability to act as a carbon sink into the future.