Stable isotope compositions of precipitation over Central Asia

Central Asia is one of the driest regions in the world with a unique water cycle and a complex moisture transport process. However, there is little information on the precipitation delta O-18 content in Central Asia. We compiled a precipitation delta O-18 database from 47 meteorological stations across Central Asia to reveal its spatial-temporal characteristics. We determined the relationship between precipitation delta O-18 and environmental variables and investigated the relationship between delta O-18 and large-scale atmospheric circulation. The Central Asia meteoric water line was established as delta H-2 = 7.30 delta O-18 + 3.12 (R-2 = 0.95, n = 727, p < 0.01), and precipitation delta O-18 ranged from +2 parts per thousand to -25.4 parts per thousand with a mean of -8.7 parts per thousand. The precipitation delta O-18 over Central Asia was related to environmental variables. The delta O-18 had a significant positive correlation with temperature, and the delta O-18-temperature gradient ranged from 0.28 parts per thousand/degrees C to 0.68 parts per thousand/degrees. However, the dependence of delta O-18 on precipitation was unclear; a significant precipitation effect was only observed at the Zhangye and Teheran stations, showing delta O-18-precipitation gradients of 0.20 parts per thousand/mm and -0.08 parts per thousand/mm, respectively. Latitude and altitude were always significantly correlated with annual delta O-18, when considering geographical controls on delta O-18, with delta O-18/LAT and delta O-18/ALT gradients of -0.42 parts per thousand/degrees and -0.001 parts per thousand/m, respectively. But both latitude and longitude were significantly correlated with delta O-18 in winter. The relationship between delta O-18 and large-scale atmospheric circulation suggested that the moisture in Central Asia is mainly transported by westerly circulation and is indirectly affected by the Indian monsoon. Meanwhile, the East Asian monsoon may affect the precipitation delta O-18 content in westerly and monsoon transition regions. These results improve our understanding of the precipitation delta O-18 and moisture transport in Central Asia, as well as the paleoclimatology and hydrology processes in Central Asia.