Abstract
<title>Abstract</title> <p>Observational studies have found that the El Niño-Southern Oscillation (ENSO) significantly affects the North Atlantic atmospheric circulation in the early winter season (November-December), favouring seasonal-mean circulation anomalies that project onto the East Atlantic Pattern (EAP). Recent analyses have found that this teleconnection has changed across different epochs, which has relevant implications for seasonal predictability in the North Atlantic and Europe. However, these analyses were solely based on observations, and the limited length of the instrumental period poses a heavy constraint on a robust assessment of whether this multidecadal variability is indeed significant and what its underlying dynamical mechanisms are. In this study, we address these two important questions by using long pre-industrial control simulations, which allow us to overcome the constraints related to small sample sizes in the observations. Our results show a significant chance that the multidecadal variability of the ENSO-EAP teleconnection is not explained just by sampling variability, but is likely driven by dynamical mechanisms. While the analysis of individual models reveals a high degree of uncertainty in the teleconnection and the mechanisms driving its multidecadal variability, changes in the tropical Indian Ocean convection, PDO phase and background state of the jet stream emerge as potential mechanisms explaining the non-stationarity of the teleconnection. These results enhance our understanding of seasonal variability and predictability in the North Atlantic and Europe.</p>