The relations between summer droughts/floods and oxygen isotope composition of precipitation in the Dongting Lake basin

The stable oxygen isotope composition of precipitation (δ¹⁸O_p) in southern China is considered as a valuable proxy of climatic conditions. However, their interpretations have been controversial. In this study, based on the observed and simulated data (isoGSM2) on oxygen isotope composition of precipitation, the linkage between summer precipitation (P) and δ¹⁸O_p in the Dongting Lake basin and their possible influencing factors were investigated. The results indicate that the interannual variation of summer δ¹⁸O_p is consistent with that of annual δ¹⁸O_p. They both show a significantly negative correlation with the summer P, suggesting that the stable isotope composition in precipitation may be considered as a proxy of summer precipitation in the Dongting Lake basin. Statistically, the amount effect and circulation effect are significant in the isotope composition of precipitation in the basin. Based on either the observed data in Changsha or the simulated data for the basin, the local amount effect appears more important than large-scale circulation for δ¹⁸O_p during extreme summers. These results can potentially improve the reconstruction of paleoclimate in the East Asian monsoon region. Further study is needed to determine the contribution of local and large-scale factors to the oxygen isotope composition of precipitation and to quantify the integral rainout along the moisture transporting paths.