Impact of the equatorial Atlantic on ENSO prediction in SEAS5-20C re-forecast

El Niño-Southern Oscillation (ENSO) is one of the most globally relevant modes of climate variability, playing a crucial role for tropical and extratropical seasonal predictions. During certain decades, specifically in the early and late 20th century, ENSO is coupled with the Atlantic Niño. Since the Atlantic Niño exhibits its maximum variability during the boreal summer (JJA), while ENSO peaks in winter (DJF), it has been shown that the Atlantic Niño can act as a predictor for ENSO in certain decades. This linkage operates on an interannual scale by alterations in the Atlantic Walker cell and, at decadal scales it has been related with changes in certain patterns, such as the Atlantic Multidecadal Variability (AMV), and an increase in pantropical oceanic variability. Nevertheless, further research on the mechanisms of this connection is needed.

This work analyzes this Atlantic-Pacific connection in SEAS5-20C, as well as the decadal and interannual mechanisms that underpin this connection. Furthermore, it discusses the influence of this connection on the decadal variability of ENSO and Atlantic Niño predictive skill. It is found that decadal changes in tropical basin interactions coincide with changes in the predictability of the tropical Atlantic and Pacific. These findings reveal how the connection between tropical basins is associated with improvements in ENSO and Atlantic Niño predictions.