Tropical Atlantic modulation of the ENSO teleconnection to the North Atlantic

The El Niño-Southern Oscillation (ENSO) teleconnection towards the Tropical North Atlantic (TNA) represents a robust response, where sea surface temperatures (SST) are positively correlated with ENSO. Following the peak of TNA SST anomalies (SSTAs) in the decaying phase of ENSO, the TNA can influence the local Walker circulation, creating a Rossby Wave Source (RWS) over the Caribbean region in boreal spring and summer. Additionally, when combined with the Pacific SSTAs, this Walker cell perturbation forms the Pacific-Caribbean Dipole (PCD), acting predominantly in the developing phase of ENSO and impacting the North Atlantic European (NAE) region. However, the influence of the TNA SSTAs on the Caribbean RWS and resulting NAE perturbation in the decaying phase of ENSO remains unclear. Thus, we use a series of sensitivity experiments with a simplified atmospheric general circulation model to determine how the TNA modulates the inter-basin teleconnection and how this modulation can influence the NAE response. We find that the NAE region is modulated by the TNA SSTA and Caribbean region in the boreal spring and summer. In boreal spring, a propagating Rossby wave train modulates the NAE region, while in boreal summer, the influence is nonlinear and tends to strengthen ENSO’s influence in the NAE region. Overall, our analysis presents a deeper understanding of the inter-basin Walker cell interactions in the decaying phase of an ENSO event and the TNA’s modulation of the teleconnection to the NAE region.