[Seminar on Aug 20] Causes of precipitation changes in Central Asia since the Last Glacial Maximum
Dr. Xiaojian Zhang
10am, Aug 20, 2018
New Building 1118, IAP
There are significant differences in the interpretation of the moisture (precipitation) history of Central Asia since the Last Glacial Maximum (LGM), as inferred on one hand from speleothem oxygen isotope records, and on the other from lake sediments and loess-paleosol sequences. This talk will discuss precipitation changes in Central Asia since the LGM and their control factors using results from the “Simulation of Transient Climate Evolution over the last 21,000 years”. Transient simulations reveal that a wet climate occurred during the LGM, the B？lling-Aller？d warm period, and the middle Holocene, and a dry climate occurred during Heinrich event 1, the Younger Dryas, and the early Holocene in this area. These changes were mainly controlled by Earth's orbital parameters, meltwater discharges into the oceans and continental ice sheets. The contribution of GHG concentrations to precipitation changes was minor. External forcing factors influenced the precipitation mainly through affecting the water vapor input from the North Atlantic and Mediterranean Sea, and vertical motions of the atmosphere over Central Asia. The North Atlantic Oscillation was an important atmospheric bridge connecting the external forcings to precipitation changes in Central Asia.