Inter‐Basin Interaction Between Variability in the South Atlantic Ocean and the El Niño/Southern Oscillation

Abstract

AbstractOceanic variability that interacts with the El Niño/Southern Oscillation (ENSO) has been well identified in most ocean basins; however, the effect of variability over the South Atlantic (SA) on the ENSO is unknown. This study demonstrates that dominant mode of subtropical SA sea surface temperature (SST) variability during the boreal winter, referred to as the South Atlantic Subtropical Dipole (SASD), contributes to occurrence of an El Niño a year later. During a positive SASD, low‐tropospheric anticyclonic circulation anomalies over the mid‐latitude SA reduce convective activities over southeastern South America. The low‐tropospheric divergence anomalies associated with the reduced convection attenuate the occurrence of South American Low‐Level Jet, and moisture supply is directed along the South Atlantic Convergence Zone (SACZ). The increased precipitation over the SACZ leads to an anomalous surface easterly that lowers the SST over the equatorial Atlantic and eventually modulates the zonal Walker circulation, thereby favoring El Niño development.