Modelling the effect of northward migration of a high Proto-Tibetan Plateau on East Asian and inland Asian summer climate

In the present study, four numerical simulations were conducted to investigate the East Asian and inland Asian summer climate response to the northward migration of a high Proto-Tibetan Plateau, a new evolution model of Tibetan Plateau from Eocene to early Miocene supported by recent geological evidences. The results demonstrated that when the southern margin of the high Proto-Tibetan Plateau migrates from 22°N (early Eocene) to 29°N (Post-early Miocene ), the summer precipitation throughout East Asia was intensified, with its impact extending to 60°N and the most remarkable precipitation change in Southern China. However, the summertime rainfall in inland Asia between 40°N and 50°N was significantly decreased due to the northward migration of the Proto-Tibetan Plateau, intensifying inland Asia aridity. These summer precipitation anomalies in East Asia and inland Asia corresponded well with the summer water vaper transportation, vaper convergence and vertical movement anomalies. The northward migration of the high plateau also alternated the intensity and position of diabatic heating and mid-latitude westerly jet over the plateau, which exerted profound influence on East Asian and inland Asisan summer climate.

The regional climate effect of the northward migration of a high Proto-Tibetan Plateau in our simulations has at least two implications for East Asian and inland Asian climate change before the early Miocene. First, the result in Southern China is consistent with a recent megafossils study, which showed increased rainfall seasonality from middle Eocene to middle Oligocene in Southern China. Second, the intensified inland Asian aridity indicated that the desert expansion and dust generation in inland Asia may have initiated much earlier than previously thought, i.e. 25-22 million years ago, supported by several recent geological observations. Thus, this study could shed light on a new perspective of the tectonic-climate relationship.