Miocene East Asia summer monsoon precipitation variability and its possible driving forces

The East Asian summer monsoon (EASM) precipitation is vital to hydrology, ecology and societal activities in the densely populated region of East Asia. However, its long-term evolution history and driving forces during the relatively warm Miocene remain unclear, even conflicting in some intervals. Here, we present a new, and quantitative record of EASM precipitation during Miocene using the Bayesian approach of Climate Reconstruction Software (CREST) based on pollen flora from the Tianshui Basin located on the northwestern Tibetan Plateau (TP). The results demonstrate that a strong and relatively stable EASM precipitation period occurred during the Neogene in northern China at similar to 17.1-13.6 Ma, which was followed by a strong and gradual decreasing period between similar to 13.6 and 7.4 Ma. This trend was abruptly stopped at similar to 7.4 Ma with the beginning of a period of large amplitude precipitation increase. The comparison analysis reveals that the gradual decrease of EASM precipitation during the period of similar to 17.1-7.4 Ma was primarily controlled by the global cooling, whereas the significant increase period after similar to 7.4 Ma was mainly related to the late Miocene uplift of the TP, supporting climate model simulations, in which both the global temperature and palaeogeography play important roles in regulating the long-term evolution of EASM precipitation.

Automated summary

A new quantitative record of East Asian summer monsoon (EASM) precipitation during the Miocene was presented using the Bayesian approach, revealing a period of stable precipitation followed by a decreasing trend, and then a significant increase around 7.4 million years ago. The gradual decrease in EASM precipitation was primarily influenced by global cooling, while the significant increase was related to the late Miocene uplift of the Tibetan Plateau.