"The project proposed here aims at improving the dynamical understanding of the subpolar gyre circulation in the North Atlantic Ocean. The primary research tools are numerical modeling and state-of-the-art statistical and physical analyses.Advance in this field is important because the subpolar gyre is a key region for decadal climate variability and therefore related to many changes that impact human societies and economies in this region. Demand for improved decadal predictions has increased in recent years. Many research institutions are currently designing elaborate numerical prediction systems for climate services. However, the performance of climate models with respect to the subpolar gyre has not been investigated yet. Previous work suggests large differences in the simulated dynamics and variability, limiting the prediction skill.We propose the first time intercomparison of this circulation system in comprehensive climate models. Moreover, we will perform specifically designed experiments with coupled and uncoupled climate models to investigate how decadal climate variability is generated by atmosphere-ocean exchanges, and to quantify the importance of different physical fluxes and different regions. In order to make our results available and facilitate their application, they will be conceptualized in a mathematical model, a minimal prediction system. This mechanistic understanding complements large numerical prediction efforts at partner institutions.The project is motivated by a novel understanding of historic climate changes that the applicant developed during his doctoral studies. We will take this idea as a promising starting point, scrutinize the underlying dynamics and develop this approach into a useful model of climate variability. The applicant will receive complementary training in the necessary skills. He will also improve his educational and outreach skills for which the host is exceptionally well prepared."