Spatiotemporal differences in Holocene climate change in the Yarlung Tsangpo catchment, southern Tibetan Plateau, reconstructed from two sandy loess sequences

Abstract

The southern Tibetan Plateau is influenced by several atmospheric circulation systems, which combined with the complex topography results in variable environmental conditions from east to west. We investigated the spatiotemporal variability of the Holocene climate of this region based on analyses of two sandy loess sequences in the complex valley environment of the upper and mid-lower reaches of the Yarlung Tsangpo (YT) catchment. OSL dating with the single-aliquot regeneration protocol was used to establish a chronological framework, and analyses of element geochemistry, grain size, magnetic susceptibility, and chromaticity were conducted to reconstruct changes in the environment and climate during the Holocene. The results show that the deposition of sandy loess deposits was widespread from east to west in the YT catchment, especially after 8.3 ka. The proxy records suggest more complex precipitation and temperature patterns in the western loess region than in the eastern loess region of the YT catchment. After 8.3 ka, loess deposition in the western valley was more strongly influenced by the westerlies, while the climate of the eastern region was dominated by the Indian summer monsoon. Our results demonstrate significant Holocene climate variability between the eastern and the western regions. We suggest that the loess deposits in the YT catchment are a potentially valuable archive of information for understanding the complex interaction between the westerlies and the Asian monsoon during the Holocene.