Sedimentary record of Holocene hydroclimatic changes from a mountainous lake on the southeastern Tibet Plateau

The Tibetan Plateau (TP) contains the largest amount of snow and glacial ice outside the polar regions. Recent global warming poses an existential threat to the TP region, which has led to remarkable changes in regional hydrological conditions, e.g. lake expansions, accelerated glacier melting, thereby causing higher-frequency hydrological hazard events, including floods and debris flows. Knowledge of long-term climate changes and hydrological responses is essential for managing water resources going forward and assessing the potential impacts of future climate changes on the TP. In this study, we conducted high-resolution X-ray fluorescence (XRF) analyses and measured major and trace elements, total organic carbon (TOC) and magnetic susceptibility (MS) in a 20.47-m sediment core, dated 7.00 kaBP, from Lake Basongcuo, southeastern TP, to infer hydroclimate changes and identify extreme flooding events over the past 7ka years. The results suggest that the interval 7.00–6.05 cal ka BP was marked by warm and wet conditions. The following period, 6.05–3.80 cal ka BP, was characterized by lake deepening under moderately warm and wet conditions. Rapid changes in multiple climate proxy variables 3.8 cal ka BP indicated the termination of the warm/wet period at the onset of the Late Holocene. A cooling and drying trend occurred after 3.8 cal ka BP and persisted until an increase in temperature and precipitation began about 0.1 cal ka BP. The Basongcuo record displays similarities to other paleoclimate records from the southern and central TP, suggesting coherent millennial-scale hydroclimate changes across the region that were controlled mainly by the variations in the intensity of the Indian Summer Monsoon and the position of the Intertropical Convergence Zone. Moreover, 14 extreme flood events were identified, which can be divided into two types: rainstorm flood events triggered by monsoon precipitation and rain-on-snow (ROS) floods triggered by rainfall combined with snowmelt.