The climatic drivers of tropical rainfall and atmospheric circulation in the late Pleistocene are still debated. Some studies suggest that tropical precipitation primarily responded to precession (23–19 ky cycle), whereas others propose that glacial-interglacial (100 ky) changes in ice sheets and sea level dominate. Here we re-examine orbital influences on tropical-to-subtropical precipitation isotopes using singular spectrum analysis to isolate leading oscillatory modes from proxy records across the Indo-Pacific Warm Pool (IPWP) and Asian monsoon domain. We find that the IPWP, Bay of Bengal, and South China Sea are dominated by the 100 ky glacial-interglacial mode of variability, whereas eastern China clearly follows precession, suggesting that precipitation isotopes over the mid-latitude Asian continent respond to different mechanisms than those in the IPWP or Indian and East Asian monsoon regions. This study demonstrates that glacial cycles, rather than changes in local insolation, are the dominant driver of Pleistocene IPWP hydroclimate.

Plain Language Summary

Reconstructions of past changes in rainfall, derived from cave deposits and ancient leaf waxes, provide an opportunity to understand how the tropical Indo-Pacific Warm Pool, located between southeast Asia and Australia, responds to large-scale changes in global climate. Here we statistically analyze five long records of rainfall and atmospheric circulation across the Warm Pool, the Indian and East Asian monsoon regions, and eastern China to isolate different external drivers of change between regions for the last 600,000 years. We find that the signal over eastern China is dominated by seasonal changes in solar radiation over mid-latitudes in the Northern Hemisphere, whereas the signal in the Warm Pool and monsoon regions are dominated by changes in sea level and high latitude ice sheet growth. This clear spatial difference in the external drivers of regional circulation changes suggests that the cave records from China do not exclusively reflect East Asian monsoon rainfall. Additionally, this study supports a strong connection between high and low latitude climates during the last several hundred thousand years.