A stable isotope record from freshwater lake shells of the eastern Tibetan Plateau, China, during the past two centuries

Lake Xingcuo is a small, closed, hardwater lake situated in the eastern Tibetan Plateau. Stable isotope data (delta O-18 and delta C-13) from the freshwater snail Gyraulus sibirica (Dunker) in a 34-cm-long, radioactive isotope-dated sediment core represent the past 200 years of Lake Xingcuo environmental history Carbon and oxygen isotope ratios in the shells of the snail yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the snail's life-span. Living and fossil shells from Lake Xingcuo were collected. delta O-18 values in the living shells from Lake Xingcuo are in equilibrium with ambient waters, while delta C-13 values may trace snail dietary carbon. On comparing delta O-18 and delta C-13 in the shell of Gyraulus sibirica with monitored data for the period 1954-1995, we found that the delta O-18 composition in the shell is an efficient proxy revealing air temperature during the warmer months from April to September. There is a positive correlation between the delta O-18 in the shells of Gyraulus sibirica and the running average temperature of the warmer months. Climatic variability in the eastern Tibetan Plateau for the past two centuries has been inferred from the delta O-18 record from the freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years' palacoclimatic record for this region can be separated into three periods representing oscillations between warm and cool conditions consistent with the Guliya ice record in the Tibetan Plateau