Unveiling the impacts of winter Atlantic Niño/Niña on the ENSO decay pace

El Niño-Southern Oscillation (ENSO) is the pronounced interannual variability with tremendous impacts on global climates. As varying ENSO decay pace results in significantly different climate impacts, understanding the factors responsible for ENSO decay is vital for improving the prediction of ENSO evolution and its climate effects. Here we show the sea surface temperature (SST) variability peaking in boreal winter over the equatorial Atlantic, dubbed as winter Atlantic Niño/Niña, regulates ENSO decay pace via modulating trans-basin Walker circulation. Both observational analyses and pacemaker experiments demonstrates that El Niños concurrent with preceding winter Atlantic Niño would decay rapidly, while those with a winter Atlantic Niña tend to decay slowly. Analogously, La Niñas would undergo a prolonged attenuation following a winter Atlantic Niño but evanish rapidly following a winter Atlantic Niña. Our results highlight the winter Atlantic Niño/Niña as a crucial factor modulating ENSO decay pace, offering valuable insights for improving seasonal forecasts of ENSO phase transition.