Climatic Signals in the Last 200 Years from Stable Isotope Record in the Shells of Freshwater Snails in Lake Xingcuo,Eastern Tibet Plateau,China

Lake Xingcuo is a small closed,hard-water lake ,situated on eastern Tibet Plateau.Stable isotope data(δ^18O and δ^13C) from the freshwater snail Gyraulus sibirica(Dunker)in a34 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 δ18^O values of modern shells from Lake Xingcuo are in equilibrium with high δ^13CTDIC.By calibrating δ^18O and δ^13C in the shell Gyraulus sibirica(Dunker)with in-strument-measured data for the period 1954-1992,we found that the δ^18O 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 δ^18O and the run-ning average temperature in the warmer half-yiar period.Climatic variability on eastern Tibet Plateau,for the last two centuries,has been successfully inferred from the δ^18O record in freshwater snails in the sediments of Lake Xingcuo.As such,the last 200 years of palaeocli-matic 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.

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

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 δ¹³C_TDIC 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. This study was supported by the Key Innovation Project of the Chinese Academy of Sciences (KZCX1-10-02), the National Natural Science Foundation of China (Grant No. 49803001), and the China National ‘973’ Project (No. G1998040810).