The Footprint of the 11-Year Solar Cycle in Northeastern Pacific SSTs and Its Influence on the Central Pacific El Niño

Applying statistical analyses to reanalysis products during the period 1900–2018, this study finds the 11-year solar cycle to have a significant correlation with sea surface temperature (SST) variations in the Northeastern Pacific. The solar influence is first manifested and amplified in the lower stratosphere, which then alters the strength of Hadley circulation in the troposphere. Lastly, the changes in the sinking branch of the Hadley circulation modulate surface heat fluxes to give rise to the SST footprint. The footprint has a structure similar to that of the Pacific meridional mode (PMM) that is known to be an important trigger of the central Pacific (CP) type of the El Niño-Southern Oscillation (ENSO). The 11-year solar cycle is thus shown to contribute to the slow modulation of the CP ENSO and, in particular, to be associated with more CP El Niño (La Niña) events during the active (inactive) phase of the cycle.