Oxygen and carbon isotope patterns archived in shells of the aquatic gastropod Radix: Hydrologic and climatic signals across the Tibetan Plateau in sub-monthly resolution

The shell patterns exhibit an increasing influence of precipitation and a decreasing influence of evaporation on the isotope compositions from west to east. δ18O values of shells from lakes on the eastern and central TP (Donggi Cona, Yamdrok Yumco, Tarab Co) mirror monsoon signals, indicated by more negative values and higher variabilities compared to the more western lakes (Karakul, Bangong/Nyak, Manasarovar). In Yadang Co, located on the central southern TP, the monsoon rains did not reach the lake in the sampling year, although it is located in a region which is usually affected by monsoon circulation. The δ18O values are used to differentiate the annual hydrological cycle into ice cover period, melt water period, precipitation period and evaporation period. δ13C compositions in the shells particularly depend on specific habitats, which vary in biological productivity and in carbon sources. δ18O and δ13C patterns show a positive covariance in shells originating from large closed basins. The results show that Radix shells mirror general climatic differences between the seven lake regions. These differences reflect both regional and local climate signals in sub-seasonal resolution, without noticeable dependence on the particular lake system.