Westerly jet stream controlled climate change mode since the Last Glacial Maximum in the northern Qinghai-Tibet Plateau

Abstract

Climate change from the northern Qinghai-Tibet Plateau (QTP) is affected by the combined effects of the Asian summer monsoon and the westerlies. However, changes in monsoon vapor transport and the westerly jet stream, as well as their effect to climate change mode there, are not clear at different time scales. Here we present composite research using paleoclimate reconstructions and ensemble simulations since the Last Glacial Maximum (LGM) on the basis of an eolian sedimentary sequence in the northern QTP. Results from 317 surface sediment samples show that pedogenic carbonate δ18O is affected both by precipitation and temperature, and organic carbon isotope (δ13Corg) reflects the vegetation growth status in areas where precipitation is greater than 290 mm. Proxies from the sedimentary sequence and the Paleoclimate Modeling Intercomparison Project 3 (PMIP3) simulations show a close relationship between climate change mode in the northern QTP and the westerly jet stream whose movement is triggered by warm or cold conditions in the high-latitude regions. That is, when the climate is in cold/glacial period the westerly jet stream strengthens and moves southward, and the mountains become wetter. This climate change mode can be validated by records from mountains of North America and Africa. According to the CMIP5 simulations, the westerly jet stream will strengthen in the future, and climate in the northern QTP and the high-altitude region of the mid-latitudes will become wetter with global warming.