Spatiotemporal Variations of Asian Summer Monsoon Subsystems During the Late Miocene‐Early Pliocene

Abstract The Asian summer monsoon plays an important role in the Southeast Asia climate, which is affected by both the East Asian summer monsoon (EASM) and the South Asian summer monsoon (SASM) subsystems. However, the spatiotemporal evolution of the Asian summer monsoon subsystems remains unclear between the late Miocene and early Pliocene. Here, biomarkers and environmental magnetic proxies from Ocean Drilling Program Site 1143 are used to reconstruct the 8.5–4 Ma paleohydrological evolution of Southeast Asia, which indicates a gradual wetter climate from 8.5 to 5.3 Ma and an overall drying climate since 5.3 Ma. The declined atmospheric CO 2 during the late Miocene facilitated the intensification of SASM, leading to its emergence as the prevailing monsoon system in Southeast Asia. In the early Pliocene, warming of the eastern equatorial Pacific promoted the western Pacific subtropical high to shift westward, which led to a prevailing EASM in Southeast Asia. Our findings improve the understanding of the behavior of EASM and SASM subsystems and their underlying mechanisms during the late Miocene‐early Pliocene.