Tibetan Plateau Uplift Changed the Asian Climate and Regulated Its Responses to Orbital Forcing During the Late Eocene to Early Miocene

The Tibetan Plateau (TP) uplift is believed to influence the Asian climate evolution on tectonic timescales throughout the Cenozoic era, whereas the orbital cycles on much shorter orbital timescales. However, the specific role of the former in modulating Asian climate responses to the latter remains inadequately understood, hindering our comprehension of the Asian climate evolution. To tackle this issue, we simulated the Asian climate by using the Community Earth System Model version 1.2.2 for two key periods: the late Eocene-early Oligocene and the late Oligocene-early Miocene. The simulations show that the TP uplift not only strengthened the Asian monsoon (AM), resulting in more annual and summer precipitation due to its elevated heating but also significantly amplified eccentricity-precession forcing and minorly weakened obliquity forcing on the Asian climate. Given a relatively lower and smaller TP during the late Eocene-early Oligocene, the northern East Asian precipitation is little influenced by eccentricity-precession cycles, in contrast to previous reconstruction records. This implied a relatively higher and/or larger TP might have existed at that time. As the TP continued to rise in the late Oligocene-early Miocene, East AM precipitation became more sensitive to rising summer insolation, with precipitation increasing in the southern region while decreasing in the northern region. These findings emphasize the significance of taking the TP uplift into account when examining the influence of orbital forcing on the Asian climate during the Cenozoic.