Glacial-Interglacial Shifts Dominate Tropical Indo-Pacific Hydroclimate During the Late Pleistocene

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 reexamine 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 drivers of Pleistocene IPWP hydroclimate.