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Abstract

While the influence of El Niño-Southern Oscillation (ENSO) on the tropical Atlantic has been well established, recent studies have suggested that sea-surface temperature (SST) anomalies in the tropical Atlantic can, in turn, excite ENSO events. The importance of this influence, however, remains uncertain, with a few recent studies suggesting that it is weak or even just a statistical artifact. Here we use numerical experiments with the GFDL CM 2.1 general circulation model (GCM) to shine new light on this issue. Our approach relies on a combination of perfect model hindcasts and pacemaker experiments, i.e., we restore SST to climatology in selected basins during perfect model hindcasts.The experiments show that developing ENSO events are not sensitive to SST anomalies in the tropical Atlantic. The decay of ENSO events, on the other hand, can be substantially accelerated by SST anomalies in the tropical Atlantic. Perhaps most strikingly, SST anomalies in both the equatorial and northern tropical Atlantic fail to develop when ENSO events are suppressed. The results suggest that, in the context of CM 2.1, the tropical Atlantic cannot initiate ENSO events. It does, however, play an important role in the termination of ENSO, and thus could be considered as a brake that is activated by ENSO itself.