What was the role of palaeogeography in East Asian monsoon evolution since the Cretaceous?

Abstract

The evolution of the East Asian summer monsoon (EASM) has been linked to the development of the Tibetan Plateau, yet monsoon simulations vary considerably between different palaeogeographic models due to inherent uncertainties in reconstructing deep-time landscapes, both locally, regionally and globally. Using the fully coupled HadCM3BL-M2.1aD palaeoclimate model, we examine EASM evolution over the past 145 Myr across three independent palaeogeographies (Getech, Scotese and Robertsons). While all simulations capture broad hydrological trends, they diverge markedly in the timing and intensity of monsoon development. The Cenozoic strengthening of the EASM aligns with Tibetan and regional mountain orogeny, but Cretaceous behaviour reflects strong remote teleconnections driven by continental configuration. These results demonstrate that Asian monsoon systems are sensitive not only to local orography but also to global palaeogeographic context due to the impact of teleconnections on the EASM. Constraining such uncertainties is essential for resolving the monsoon's long-term evolution and climatic influence.