Warm Phase of AMV Damps ENSO Through Weakened Thermocline Feedback

Interactions between ocean basins affect El Niño–Southern Oscillation (ENSO), altering its impacts on society. Here, we explore the effect of Atlantic Multidecadal Variability (AMV) ENSO behavior using idealized experiments performed with NCAR-CESM1 model. Comparing warm (AMV+) to cold (AMV−) AMV conditions, find that sea surface temperature (SST) anomalies are reduced by ∼10% and precipitation shifted west during Niño east La Niña. Using Bjerknes stability index, attribute reduction in variability a weakened thermocline feedback boreal autumn. In AMV+, Walker circulation trade winds strengthen over tropical Pacific, increasing background zonal SST gradient. The changes shift westwards, wind stress more confined west. We suggest ENSO-wind decrease strength east, eventually reducing growth rate.