Shifting influences of Indian Ocean Dipole and western Pacific subtropical high on annual precipitation δ18O in southern East Asia

Clarifying relationships between stable oxygen isotope ratios in precipitation (δ¹⁸O_p) and atmospheric circulations including the Indian Ocean Dipole (IOD) and western Pacific subtropical high (WPSH) forms the basis of paleocirculation reconstructions. However, whether the IOD and WPSH modulate interannual variations of δ¹⁸O_p remains unclear. Here, we reveal the links between the IOD/WPSH and the annual δ¹⁸O_p in southern East Asia. We found that the IOD strongly influenced annual δ¹⁸O_p before 1999 by changes in moisture supply from different transport pathways and convection. However, the link became decoupled after 1999, resulting from the transition of the IOD from a symmetric to an asymmetric pattern. In contrast, significantly enhanced WPSH emerges as an important influence on annual δ¹⁸O_p after 1999. Therefore, the IOD and WPSH alternately influence interannual variation of δ¹⁸O_p around 1999. Our findings imply that signals of IOD and WPSH should be considered in different periods to better interpret paleoclimate records.