Seasonal variability of oxygen and hydrogen stable isotopes in precipitation and cave drip water at Guilin, southwest China

The interpretation of climatic information from stalagmites has traditionally been a complex research problem, with oxygen isotopes playing a particularly important role in global climate change studies. This study investigates the relationship between oxygen isotope composition of the atmospheric in precipitation and cave drip water at Panlong cave in southwest China on seasonal timescales of variability. Time series seasonal variability was derived from Panlong cave in Guilin by collecting daily precipitation samples for stable isotope analysis during 2012. Results indicate that delta O-18 of precipitation contains a clear seasonal variation whereby higher values are mainly distributed during winter and lower values during summer. Seasonal variations in water sources affect the precipitation delta O-18 values. Drip water delta O-18 also displayed a seasonal cycle which is attenuated relative to delta O-18 of precipitation. Drip water time series display seasonal cycle ranges from 1.5 to 3.5 aEuro degrees relative to Vienna Standard Mean Ocean Water, which mainly follow the precipitation delta O-18 seasonal cycle. Seasonal variation in drip water delta O-18 supports interpretations of the stalagmite delta O-18 record as a paleoclimate proxy sensitive to the local environment. This monitoring experiment revealed that drip water must be transported through the epikarst in approximately 1.5 months during cold periods, and < 0.5 months during warm periods. Different residence time percolation is mainly affected by the atmospheric precipitation amount, depending on whether soil moisture reaches saturation.