Annual and Monthly Variations of δD andδ18 O Values in Precipitation and Drip Water and Their Relationship with Atmospheric Circulation---A Case Study in Furong Cave Area

Key words: 
• monsoon zone，meteoric precipitation，δD，δ18 O，ENSO，monsoon index /
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Abstract: Continuous monitoring was made over the hydrogen and oxygen stable isotopes ,precipitation , temperature andδD andδ18 O in the drip water and pool water in Furong cave ,Chongqing ,China from A‐pril 2011 to December 2012 ,and the characteristics of δD andδ18 O variation in precipitation and the corre‐lation with atmospheric circulations ,such as ENSO and monsoon index ,were investigated in this study . An equation of local meteoric water line (LMWL) was established ,which indicated that both its intercept and slope were significantly greater than those of global meteoric water line (GMWL) .In addition ,a nega‐tive correlation was detected between theδD andδ18 O values of local precipitation and the air temperature . The correlation coefficient betweenδ18 O values and temperature was r= -0.693 (n=20) ,while the cor‐relation coefficient betweenδ18 O values and rainfall was r= -0.121 (n=20) .The seasonal change in deu‐terium excess (d) values also showed the characteristics of being high in summer and low in winter .All the seasonal changes in d ,δD andδ18 O values of precipitation could be attributed to the difference in mois‐ture sources in different months .The hydrogen and oxygen stable isotope compositions in precipitation out of Furong cave ,a typical site in Southern China monsoon area ,were closely associated with the atmos‐pheric circulation in tropical Pacific Ocean ,such as the ENSO .When El Nino occurred ,the west Pacific subtropical high (WPSH) became stronger ,and the northwest Pacific monsoon index was high ,leading to an increase in stable isotope values in precipitation in southern China .On the other hand ,w hen La Nina happened ,the southeast trade wind was strengthened and Indian monsoon index was also high ,resulting in a decrease in stable isotope values in precipitation .