One intriguing element of the atmospheric dynamics at mid-latitudes is the presence of low-frequency variability at interannual and decadal time scales. The most well known index reflecting this dynamics is the North Atlantic Oscillation. The origin of such a dynamics is however difficult to isolate. Is it an intrinsic feature of the atmosphere variability only, or is it associated with the coupling with the slow dynamics of the ocean in the extratropics, or maybe related to the remote coupling with the Tropical Pacific? These questions are addressed in this seminar through the analysis of the dynamics of a reduced-order coupled ocean-atmosphere system. An example of solution of this system is shown at https://av.tib.eu/media/18552