Northward Extension of East Asian Summer Monsoon Since the Miocene Set by the Uplift of Tibetan Plateau.

The modern East Asian summer monsoon (EASM) features an extension from tropical to subtropical areas. However, the fundamental process that determines the northward extension of EASM in the geological history remains unclear. Here, we showed evidence from proxy data, climate modeling, and theoretical solutions that the northward extension of EASM to today's boundary emerged no later than the Miocene. The extension was driven by the monsoon seasonal march which features stepwise northward rainfall stages. The seasonal progression of monsoon was determined by Rossby wave responses from early summer to late summer and caused by the weakening of westerly jet colliding with the Tibetan Plateau (TP). The Rossby wave responses further led to a northward migration of the western Pacific subtropical high and thereby monsoon precipitation. Our findings propose a novel physical linkage between the geological evolution of EASM and the TP uplift in the context of monsoon seasonal march. Plain Language Summary: The seasonal march of the modern East Asian summer monsoon, characterized as stepwise northward rainfall stages, is one unique feature and the most fundamental process of northward extension of East Asian summer monsoon. However, its geological history and controlling processes remain unknown. Here, we found that the seasonal progression of the monsoon emerged no later than the Miocene and was driven by the uplift of the Tibetan Plateau. The emergence of the seasonality has pushed the East Asian summer monsoon northward to today's boundary. Our results provide an essential understanding of the northward extension of the East Asian monsoon climate in geological history, highlighting the role of monsoon seasonal march. Key Points: A novel physical linkage established between the East Asian monsoon climate and Tibetan Plateau uplift on the geological scaleOrographic forcing of the uplift of Tibetan Plateau determined the emergence of monsoon seasonal marchThe seasonal progression of the monsoon advanced further inland to the present boundary [ABSTRACT FROM AUTHOR]