The north tropical Atlantic (NTA) displays significant sea surface temperature anomalies (SSTA) during the ENSO decaying spring. We find that this is not always true for El Niño with moderate intensity. Nearly half of the moderate El Niño cases are followed by the strong NTA SSTAs, but others are followed by the weak NTA SSTAs, indicating the uncertainty in the connection between the moderate El Niño and the NTA. Further analysis demonstrates that El Niño, which is accompanied by the strong (weak) Aleutian low leads to the strong (weak) NTA SSTAs, suggesting that the role of the Aleutian low must be considered to fully understand the El Niño–NTA connection.
Moreover, the decadal variability in the interannual relationship between ENSO and the NTA SSTA are also examined. We identify a largely weakened impact of ENSO on the SSTA concentrated over the northeast tropical Atlantic (NETA) after the mid-1980s, while the impacts on the SSTA over the northwest tropical Atlantic (NWTA) are stable during the whole period. Further analysis indicates that the decadal changes in the ENSO–NETA connection are due to the westward shift in the ENSO-related convection and teleconnections, resulting from the westward shift of Pacific Walker circulation, induced by the intensified zonal SST gradient over the equatorial Pacific after the mid-1980s.

ENSO,north tropical Atlantic SST,Interannual variability,interdecadal change