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Abstract:
The East Asian Summer Monsoon (EASM) exhibits complex meridional precipitation patterns that shape regional hydrological cycles and societal vulnerability. However, the long-term evolution of these patterns remains poorly understood due to the complexity and uncertainties associated with paleoclimate proxies. Here, we reconstruct Holocene EASM rainfall patterns by compiling 59 speleothem δ18O records with transient isotope-enabled climate model simulations (iCESM) using the Eigen Microstate Approach (EMA). Our results show that the tripole mode of summer precipitation in eastern China underwent a reorganization during the Holocene. Throughout the Holocene, orbitally-induced asymmetric warming across the Indo-Pacific Warm Pool weakened the Walker Circulation and the Pacific–Japan teleconnection. Crucially, a systematic southward shift of the East Asian Westerly Jet blocked the intensified late-Holocene western north pacific subtropical high (WNPSH), forcing its anomalous westward extension. This high to low latitude interplay subsequently locked moisture convergence over the Yangtze River Basin, leading to a progressively narrower central anomaly of the precipitation tripole mode and eventually forming the modern tripole spatial pattern. Precipitation δ18O retains the basic spatial pattern of regional precipitation variability, while changes in moisture source contributions and transport pathways progressively reduce the contribution of the dipole mode and enhance the contribution of the tripole mode. These findings help to resolve the spatiotemporal complexity of Holocene monsoon precipitation evolution and highlight the potential of precipitation δ18O as a tracer for reconstructing the spatiotemporal evolution of East Asian hydroclimate.
