Decoupling of speleothem δ18O from East Asian summer monsoon intensity across peak interglacials: Insights from the Last Interglacial and Holocene

Comparable speleothem δ 18 O values over eastern China during past four peak interglacials suggest similar East Asian summer monsoon (EASM) intensities, but large orbital insolation and land-sea thermal contrast variations highlight varying EASM intensities, supported by loess and marine records. To resolve this paradox, we focus on the Last Interglacial (∼127 ka) and Holocene (∼6 ka) using an isotope-enabled fully coupled climate model. Our model reproduces a stronger EASM but comparable speleothem δ 18 O values during the Last Interglacial relative to Holocene. The stronger EASM, driven by enhanced land-sea thermal contrast arising from a higher insolation, induces lighter precipitation δ 18 O over eastern China via the rainout process. However, this lighter signal is overwhelmed by heavier δ 18 O arising from moisture source location and composition changes, yielding slightly heavier δ 18 O over eastern China. Our results highlight speleothem δ 18 O values retain significant but incomplete sensitivity to the EASM intensity, which helps reconcile conflicting proxies for monsoon variability and comprehensively understand past monsoon dynamics.