A change in the relationship between ENSO and the South Atlantic Subtropical Dipole in the past four decades

Abstract. This study investigates the relationship between sea surface temperature (SST) in the subtropical Atlantic Ocean, as represented by the Southern Atlantic Subtropical Dipole (SASD), and SST in the tropical Pacific Ocean, identified by the El Niño-Southern Oscillation (ENSO). Our analysis reveals a significant inverse correlation between the SASD and Niño indices over a century, with multi-decadal variability that contradicts weak simultaneous correlations previously reported in the literature. The study also highlights a strengthening of their inverse correlations in the most recent two decades compared to the preceding two decades, which can be attributed to the shift in ENSO regime from more frequent eastern Pacific El Niño to central Pacific El Niño around the turn of the century. This shift helps set the stage for changes in convective activity in the critical region (20° S–40° S, 180°–140° W) of the central South Pacific Ocean, triggering wavetrains that propagate along different paths and ultimately contributing to different southern Atlantic subtropical high (SASH) and changes in anomalous SST patterns in the subtropical Atlantic Ocean. These findings advance our understanding of the interactions between South Atlantic and Pacific SST variations, which strongly influence rainfall patterns particularly in South America and southern Africa and may improve sub-seasonal to seasonal precipitation predictions in these regions.