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 (δ¹⁸O and δ¹³C) 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. δ¹⁸O values in the living shells from Lake Xingcuo are in equilibrium with ambient waters, while δ¹³C values may trace snail dietary carbon. On comparing δ¹⁸O and δ¹³C in the shell of Gyraulus sibirica with monitored data for the period 1954-1995, we found that the δ¹⁸O 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 δ¹⁸O 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 δ¹⁸O record from the freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years' palaeoclimatic 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.