Climatic signals in the last 200 years from stable isotope record in the shells of freshwater snails in Lake Xingcuo, eastern Tibet Plateau, China

Abstract

Lake Xingcuo is a small closed, hard-water lake, situated on eastern Tibet Plateau. Stable isotope data (δ18O and δ13C) from the freshwater snailGyraulus sibirica (Dunker) in a 34 cm long, radioactive isotope-dated sediment core represent the last 200 years of Lake Xingcuo environmental history. Carbon and oxygen isotope ratios in the shells of the freshwater snail bear information on the isotopic composition of the water in which the shells were formed, which in turn characterizes the climatic conditions prevailing during the snail’s life span. Whole-shell and incremental growth data were collected from modern and fossil shells from Lake Xingcuo. The δ18O values of modern shells from Lake Xingcuo are in equilibrium with those of modern waters, while δ13C values are indicative of snail dietary carbon and a lake with high δ13CTDIC By calibrating δ18O and δ13C in the shellGyraulus sibirica (Dunker) with instrument measured data for the period 1954 – 1992, we found that the δ18O of the snail shells is an efficient indicator to reveal air temperature in the warmer half year instead of that around the whole year, and that there is a certain positive correlation between index δ18O and the running average temperature in the warmer half-year period. Climatic variability on eastern Tibet Plateau, for the last two centuries, has been successfully inferred from the δ18O record in freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years of palaeoclimatic record for this region can be separated into three periods representing oscillations between warming and cooling, which are confirmed by the Guliya ice record on the Tibet Plateau.