Biomarker Constraints on Indo-Pacific Warm Pool Temperature During the Late Pleistocene: The Role of Orbital Forcing

The Indo-Pacific Warm Pool (IPWP) exerts a major influence on global atmospheric circulation, yet the drivers of late Pleistocene IPWP sea surface temperature (SST) variability remain debated. To evaluate how IPWP temperature responds to different climate forcings, we present new SST records spanning the past 650 kyr based on three independent proxies— (Formula presented.), (Formula presented.), and Mg/Ca—from International Ocean Discovery Program Site U1482, located off northwestern Australia at the southernmost margin of the IPWP. Core top samples suggest that (Formula presented.) and Mg/Ca are biased toward austral summer, while (Formula presented.) is elevated under low-nutrient conditions. Down-core, all proxies exhibit coherent glacial–interglacial SST variations of ∼5 (Formula presented.) C, although (Formula presented.) is affected by nutrient stress during interglacials. The (Formula presented.) record shows relatively warm conditions during Marine Isotope Stage 6 compared to other glacial intervals, but this is not observed in the (Formula presented.) or Mg/Ca records. Total alkenone concentration, reflecting paleo-productivity, indicate enhanced productivity during glacial intervals and reduced productivity during interglacials. The SST proxy records are in phase with greenhouse gas and ice volume in the 100 and 41 kyr orbital bands, emphasizing tropical-high latitude climate coupling, while local precession forcing impacts seasonal SSTs. Productivity variations track both glacial-interglacial cycles and precession-driven changes in wind-driven upwelling and surface current intensity in the Indo-Pacific. Our regional synthesis highlights sea-level and shelf exposure as key drivers of IPWP SST patterns, with a more pronounced precession influence at the southern IPWP margin. Our findings demonstrate that both glacial-interglacial cycles and precession govern SST and productivity variations in the IPWP.