Multi-centennial ENSO-like variability response to solar activity during the holocene

Previous reconstructions suggest a possible correlation between solar and El Nino-Southern Oscillation (ENSO) on the centennial-millennial time scales, but the mechanism remains controversial. This study conducts Holocene transient simulations and finds a significant 350-500-year cycle of ENSO-like variability during the mid-late Holocene under solar activity forcing, supported by multiple reconstructions. This multi-centennial ENSO-like variability is caused by the solar-forced low-latitude process, not the high-latitude process or internal variability. When solar radiation increases, the subtropical Asian continent-Indian Ocean thermal contrast is enhanced, increasing precipitation over the India and Bay of Bengal, which generates easterly anomaly over the Indo-Pacific warm pool. Increased solar radiation also enhances the evaporation in the cloud-free regions of western North and South Pacific, and the moisture is transported to the Maritime Continent by easterly. This increases precipitation there and strengthens the easterly anomaly over the equatorial western Pacific, which triggers the La Nina-like state. The leading coupling process for the development of La Nina-like state is zonal advective and upwelling feedback, and poleward heat advection further amplifies the equatorial eastern Pacific cooling. Findings from this study suggests that a centennial-scale El Nino-like condition might occur under solar forcings if the forecast predicts a solar minimum at the end of the 21st century.