Palynological Evidence of Late Holocene Paleo-Monsoon in Eastern Pamir

The Tibetan Plateau, which is climatically dominated by the westerlies and the Asian monsoon, has a major influence on the atmospheric circulation and water resources of Asia. However, it remains unclear of the long-term (e.g., millennial- and orbital-scale) status and origin of the water resources in the plateau. In this study, we used the presence of a long-distance pollen component (e.g., Tsuga) in a sedimentary section from eastern Pamir as a tracer to characterize the air movements in the western Tibetan Plateau during the late Holocene. Based on modern backward trajectory analysis, we suggest that the pollen of Tsuga was transported by the paleo-monsoon from the southeastern Tibetan Plateau to eastern Pamir during the late Holocene (e.g., 3,200-1,750 cal years B.P.). Our findings provide evidence of paleo-monsoon movement and potential moisture transport paths from the southeastern Tibetan Plateau to eastern Pamir during the late Holocene. Plain Language Summary The modern climate of the Pamir area in the western Tibetan Plateau is dominated by the westerlies that supply more than 70% of the precipitation. Several glaciers occur in the Pamir area, and they are an important water source for major rivers such as the Indus, Amudarya, and Yankuet. We conducted a fossil pollen study of late Holocene sediments in the eastern Pamir area and found some airborne pollen types, including several subtropical taxa (e.g., Tsuga, Platycarya, Anacardiaceae, and Meliaceae). Backward trajectory analysis revealed that the Tsuga pollen grains were transported from the southeastern Tibetan Plateau to eastern Pamir by the paleo-monsoon during the late Holocene. The paleo-monsoon movement and potential moisture transport paths identified in this study provide a reference for monsoon simulation and atmospheric circulation monitoring in the western Tibetan Plateau.