Evidence of coupling in ocean‐atmosphere dynamics over the North Atlantic

Coupling between the ocean and the atmosphere is investigated in reanalysis data sets. Projecting the data sets onto a dynamically defined subspace allows one to isolate the dominant modes of variability of the coupled system. This coupled projection is then analyzed using multichannel singular spectrum analysis. The results suggest that a dominant low‐frequency signal with a 25–30 year period already mentioned in the literature is a common mode of variability of the atmosphere and the ocean. A new score for evaluating the internal nature of the common variability is then introduced, and it confirms the presence of coupled dynamics in the ocean‐atmosphere system that impacts the atmosphere at large scale. The physical nature of this coupled dynamics is then discussed. Key Points A coupled 25–30 year mode is present in the ocean‐atmosphere system This coupled mode is useful in extended‐range prediction The strength of the coupling and the predictability vary with the seasons