Holocene evolution of the Indian Summer Monsoon inferred from a lacustrine record of Lake Wuxu, south-east Tibetan Plateau

摘要

A continuous sediment record since 12.3 cal ka bp from Lake Wuxu (south-eastern Tibetan Plateau) was investigated in terms of the Holocene evolution of the Indian Summer Monsoon. The molar C/N ratio and stable C isotope were used to identify the source of the organic matter as well as climate conditions. The evolution of Lake Wuxu was summarized wihtin two periods. During the first period (early to mid-Holocene), the lake received increased fluvially transported materials, reflecting variation in the summer monsoon with solar insolation. The lake level declined and water residence time increased because of reduced river discharge during the second period (late Holocene) corresponding to a weakening of the summer monsoon. The organic material revealed a major contribution from lake primary productivity, which showed identical patterns with a high-resolution isotope record from Dongge Cave, as well as total solar irradiance. Our record from Lake Wuxu indicates that the Holocene evolution of the Indian Summer Monsoon has been driven by the solar forcing at decadal/centennial to millennial time scales. Furthermore, an abrupt decline in the monsoon was detected at around 4.0 cal ka bp, which is probably caused by an increased frequency of EI Nino-Southern Oscillation events.