Alternating dominance of Westerlies and East Asian winter monsoon on dust activities across the northeastern Qinghai-Tibet Plateau since 18.5 ka

Abstract

The mid-latitude Westerlies and the East Asian winter monsoon (EAWM) are two major atmospheric circulation systems influencing dust activities in the Northern Hemisphere (NH). However, the interplay between these wind systems and their effects on regional dust activities remain poorly understood. In this study, we present a well-dated aeolian sedimentary sequence from the loess section (ZES) on the southern slope of the Qilian Mountains in the northeastern Qinghai-Tibetan Plateau (NE-QTP). It provides insights into the response of dust activities to these wind systems for the last 18.5 ka. We developed a detailed chronology for ZES section based on luminescence dating of multiple signals from 29 samples (yielding a total of 87 ages). The luminescence sensitivities and element analysis of the sediments indicate a shift in dust source around 7.5 ka, contributed to a transition in the atmospheric circulation controls of the NE-QTP. Specially, our findings suggest that dust activity was likely dominated by EAWM from 18.5 ka to 7.5 ka and by the Westerlies after 7.5 ka across this area. We propose that increased NH ice volume (NHIV) significantly enhanced the EAWM via strengthening Siberian High, driving dust activities over the high mountains during the Last Deglaciation and Early Holocene. In contrast, as NHIV decreased during the middle-to-late Holocene, the EAWM weakened and retreated from this area, allowing the Westerlies to dominate dust activities. Additionally, grain-size parameters of sediments were used to infer variations in the intensities of these winds, revealing a gradual weakening of EAWM since the Last Deglaciation and a marked intensification of the Westerlies during the warm middle Holocene. Under the current global warming scenario, we predict that the Westerlies will continue to dominate dust activities across the NE-QTP, with a potential increase in dust activities if the Westerlies enhance.