Effect of precipitation seasonality on annual oxygen isotopic composition in the area of spring persistent rain in southeastern China and its paleoclimatic implication

This study examines the seasonality of precipitation amount and delta O-18 over the monsoon region of China (MRC). We found that the precipitation amount associated with the East Asian summer monsoon (EASM) in the spring persistent rain (SPR) region is equivalent to that of the non-summer monsoon (NSM). The latter contributes similar to 50% to amount-weighted annual delta O-18 values, in contrast with other areas in the MRC, where the delta O-18 of annual precipitation is dominated by EASM precipitation. Interannual relationships between the El Nino-Southern Oscillation (ENSO) index, simulated delta O-18 data from IsoGSM, and seasonal precipitation amount in the SPR region were also examined. We found that on interannual timescales, the seasonality of precipitation amount (EASM / NSM ratio) was modulated by ENSO and primarily influences the variability of amount-weighted annual precipitation delta O-18 values in the SPR region, although integrated regional convection and moisture source and transport distance may also play subordinate roles. During El Nino (La Nina) phases, less (more) EASM and more (less) NSM precipitation leading to lower (higher) EASM / NSM precipitation amount ratios results in higher (lower) amount-weighted annual precipitation delta O-18 values and, consequently, in higher (lower) speleothem delta O-18 values. Characterizing spatial differences in seasonal precipitation is, therefore, key to correctly interpreting speleothem delta O-18 records from the MRC.