Holocene moisture evolution and its response to atmospheric circulation in the southern Tibetan Plateau

Water vapor plays a crucial role in maintaining the water cycle system of the “Asian Water Tower” and the ecological environment in the Tibetan Plateau (TP). Understanding the moisture evolution in the southern TP helps reveal the mechanisms behind the surface landscape characteristics and their differentiation under the combined influence of the mid-latitude Westerlies (MLW) and the Indian summer monsoon (ISM). Here, we present two Holocene aeolian sequences in the Yarlung Zangbo River basin in the southern TP. Quartz optically stimulated luminescence dating was used to establish a chronology framework, and geochemical, grain size, and color proxies were used to reconstruct the history of moisture evolution. By combining reanalysis data and TraCE-۲۱ka climate simulation, the response of moisture evolution to atmospheric circulation during the Holocene was examined. Our results suggest significant spatial differences in the pattern of moisture evolution in the southern TP during the Holocene. In the western part of the southern TP, the moisture evolution was controlled by variations in the relative intensities of the ISM and the winter MLW, ultimately determined by changes of summer and winter insolation at ۳۰°N. During the early Holocene, this region was dominated by water vapor from the strong ISM in response to high summer insolation. The effectiveness of moisture delivery decreased abruptly at ~۷.۶ ka, most likely due to the weakening of the ISM. The influence of the winter MLW on moisture supply was negligible during this period. During the middle to late Holocene, the reduced summer insolation resulted in a gradual decrease in the ISM precipitation. With the increasing winter insolation, the intensified winter MLW penetrated into the southern TP and thus regulated the ISM-derived moisture supply. In the eastern part of the southern TP, the moisture evolution during the Holocene was primarily controlled by variations in the ISM, with a significantly reduced impact from the winter MLW. The early to middle Holocene was characterized by high precipitation, followed by a gradual decrease, which was mainly related to the southward shift of the Intertropical Convergence Zone and its rainfall belt due to changes in summer insolation at ۳۰°N. Overall, our study provides new insights into climate changes in the interaction region of atmospheric circulation in the southern TP.