Modeling East Asian climate and impacts of atmospheric CO2 concentration during the Late Cretaceous (66 Ma)

Utilizing the Community Climate System Model version 2 from the National Center for Atmospheric Research (NCAR) and the reconstructed paleogeographic data, we simulate East Asian climate in the Late Cretaceous (66 Ma) and investigate the impacts of atmospheric CO2 concentration on climate. The simulations show that the large-scale pressure systems and prevailing wind directions showed a remarkable seasonal variation over East Asia at 66 Ma, which indicates a monsoon feature over East Asia. The East Asian winter and summer monsoons showed a synchronous variation, that is, a strong (weak) winter monsoon accompanied a strong summer (weak) monsoon. At 66 Ma, there was more precipitation over the eastern coasts of Asia and less precipitation in the mid-latitudes of the inland areas, but there was no meiyu rainy belt in the subtropics of the East Asian land like the present climate. Moreover, the simulated Cretaceous climate over East Asia was warmer relative to the present day. Annual mean surface air temperature was higher over Asia at that time and close to the estimation from the geological evidence. In the Late Cretaceous, when atmospheric CO2 concentration is reduced, the East Asia climate has a significant change, with weaker winter and summer monsoons over East Asia. Annual mean surface air temperature and annual total precipitation reduce in most of land and ocean. Negative difference of surface water budget appeared mainly in the eastern part of East Asia, indicating a drier soil surface, while positive differences appeared in the mid‐latitudes of central-western Asia, indicating a wetter soil surface.