Quantitative recuperation of climatic sequences for the last 200 years in Xingcuo Lake, eastern Tibetan Plateau

The functional relation between the δ18O values in the shell of gastropodGyraulus sibirica and the air temperature in the warm half-yearly period, and that between Sr/Ca ratio and the precipitation in the warm half-yearly period were established by calibrating the δ18O aδ13C values, Sr/Ca ratio and Mg/Ca ratio in the shellGyraulus sibirica, as well as the total organic carbon (TOC) and its δ13C values in the Xingcuo Lake sediment in the eastern Tibetan Plateau. The sequences of air temperature and precipitation in the last 200 years in the region were quantitatively recuperated on this basis. The results showed the following: (i) There was a negative correlativity between Sr/Ca ratio and the precipitation in the warm half-yearly period, its correlation coefficient was 0.86. (ii) There was an obviously positive correlativity between index δ18O and the running average temperature in the warm half-yearly period, its correlation coefficient was 0.89. (iii) Evolution of the air temperature and the precipitation in the last 200 years can be divided into three phases distinctly. The precipitation in the later mid-19th century was 220 mm higher than that today; the air temperature in the warm half-yearly period was 2°C lower than that of the present. The precipitation in the minimum air temperature period of the early 20th century was below that today by 60 mm, and the air temperature in the warm half-yearly period was 3.4°C lower than that today, (iv) An evidently warming and drying trend existed in the last five decades.