The water vapor source in Central Asia (CA) during the middle Miocene Climatic Optimum (MMCO) is debated. We investigated the Duolebulejin (DLB) section in the Junggar Basin, dated to 18.8–13.2 million years ago (Ma), to reconstruct the history of the vegetation using analyses of multiple indices including pollen, soil organic matter carbon isotopes (δ¹³C_SOM) and magnetic susceptibility (MS). Results reveal a significant regional C₄ vegetation expansion during 15.5–14.0 Ma, which was linked to a shift in the configuration of precipitation, manifested by higher seasonality and more summer precipitation under a climatic context conducive to the growth of C₄ plants. The water vapor trajectory revealed by paleobotanical data from Eurasia, together with other paleoclimate records, suggests that the synchronous intensification of the Indian summer monsoon (ISM) may have been responsible for this shift. Combining with climate simulations and other evidence, we argue that the summer precipitation pattern in CA during the warming middle Miocene was modulated by the ISM via the monsoon-westerly interactions at high and low latitudes.

中新世中期气候最佳 (MMCO) 期间中亚 (CA) 的水汽来源存在争议。我们调查了准噶尔盆地多勒布勒金 (DLB) 剖面，可追溯到 18.8-1320 万年前 (Ma)，通过分析包括花粉、土壤有机质碳同位素 (δ 13 C SOM) 在内的多个指标来重建^植被的_历史) 和磁化率 (MS)。结果显示，在 15.5–14.0 Ma 期间区域 C ₄植被显着扩张，这与降水结构的变化有关，表现为在有利于 C 4 生长的气候背景下更高的季节性和更多的夏季_降水植物。来自欧亚大陆的古植物学数据揭示的水汽轨迹以及其他古气候记录表明，印度夏季风 (ISM) 的同步增强可能是造成这种转变的原因。结合气候模拟和其他证据，我们认为中新世变暖期间 CA 的夏季降水模式是由 ISM 通过高纬度和低纬度的季风-西风相互作用调制的。