Amplification of the NTA's Impact on ENSO: The Important Modulation by VM

The springtime North Tropical Atlantic (NTA) sea surface temperature (SST) anomaly serves as a crucial extratropical precursor to the El Niño–Southern Oscillation (ENSO), helping to alleviate the spring predictability barrier of ENSO. While the influence of the NTA on ENSO has been gradually strengthening since the mid-20th century, this trend cannot be explained by global warming. This study reveals that the Victoria Mode (VM) in the North Pacific is the key driver of this intensification. Since the mid-20th century, the negative phase of the VM has progressively strengthened, which in turn has enhanced the coupled subtropical northeasterly trade winds. This enhancement has intensified air-sea coupling over the subtropical northeastern Pacific. Consequently, atmospheric anomalies excited by the spring NTA are now more likely to imprint significant SST anomalies onto this critical hub region in the subtropical northeastern Pacific. Through intensified local air-sea interactions, these anomalies are then further transmitted into the tropical Pacific, ultimately triggering ENSO events. Our findings demonstrate that the influence of the North Tropical Atlantic on the tropical Pacific is largely modulated by the background climatic state of the North Pacific.