Interactive forces of temperature and topographic uplift shaped the East Asian monsoon rainfall evolution since the Oligocene

<p>The debate concerning the long-term evolution of the East Asian summer monsoon (EASM) and its governing mechanisms persists, often attributed to either the uplift of the Tibetan Plateau or global temperature changes. This disagreement arises from the scarcity of comprehensive, high-resolution monsoon records. Utilizing continuous sedimentary records from the South China Sea and a weathering-rainfall-temperature regression model, we have quantified the evolution of EASM rainfall in South China since 30 Ma. Our findings indicate that, apart from a notable and sustained increase in monsoon rainfall between approximately 21 and 13 Ma, rainfall patterns generally mirrored global temperature trends, suggesting that global climate change was the primary controlling factor. Based on model simulations, we attribute the anomalous enhanced EASM during ~21‒13 Ma primarily to the dominant influence of the major uplift of the Himalaya-Tibetan Plateau, with temperature effects playing a limited background role. This topographic change disrupted the close coupling between temperature and rainfall, resulting in a relatively humid and habitable East Asia despite the ongoing global cooling trend since the late Miocene. This study clearly disentangles the roles of long-term temperature regulation and the short-term impacts of Himalaya-Tibetan Plateau uplift on the evolution of the EASM since 30 Ma.</p>