Changes in the depth of Lake Qinghai since the last deglaciation and asynchrony between lake depth and precipitation over the northeastern Tibetan Plateau

摘要

As a transitional region between arid and semi-arid areas, and the climatic junction where the Asian summer monsoon and the Westerlies interact strongly, the climatic pattern of northeastern Tibetan Plateau has always been the focus of paleoclimate research. In this study, the changes in the lake depth of Lake Qinghai on the northeastern Tibetan Plateau were reconstructed from analyses of biomarkers in sediment records from the center of the lake and aeolian deposits on its southern bank. On millennial scale, the lake depth showed a fluctuating upward trend from the minimum depth at 15.6 ka to the maximum depth at 5.9 ka, revealing an overall warming-wetting pattern since the last deglaciation. Compared to the typical monsoon-dominated areas, the relatively humid late Holocene of Lake Qinghai appears to have been related to a weakened evaporation on the long-term trend. We show that on a long-term scale, precipitation may control the rate of changes in lake depth. This reasonably explains the asynchrony of precipitation and lake depth over the northeastern Tibetan Plateau during the mid-Holocene.