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 δ(18)O content in Central Asia. We compiled a precipitation δ(18)O database from 47 meteorological stations across Central Asia to reveal its spatial-temporal characteristics. We determined the relationship between precipitation δ(18)O and environmental variables and investigated the relationship between δ(18)O and large-scale atmospheric circulation. The Central Asia meteoric water line was established as δ(2)H = 7.30 δ(18)O + 3.12 (R(2) = 0.95, n = 727, p < 0.01), and precipitation δ(18)O ranged from +2‰ to −25.4‰ with a mean of −8.7‰. The precipitation δ(18)O over Central Asia was related to environmental variables. The δ(18)O had a significant positive correlation with temperature, and the δ(18)O-temperature gradient ranged from 0.28‰/°C to 0.68‰/°C. However, the dependence of δ(18)O on precipitation was unclear; a significant precipitation effect was only observed at the Zhangye and Teheran stations, showing δ(18)O-precipitation gradients of 0.20‰/mm and −0.08‰/mm, respectively. Latitude and altitude were always significantly correlated with annual δ(18)O, when considering geographical controls on δ(18)O, with δ(18)O/LAT and δ(18)O/ALT gradients of −0.42‰/° and −0.001‰/m, respectively. But both latitude and longitude were significantly correlated with δ(18)O in winter. The relationship between δ(18)O 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 δ(18)O content in westerly and monsoon transition regions. These results improve our understanding of the precipitation δ(18)O and moisture transport in Central Asia, as well as the paleoclimatology and hydrology processes in Central Asia.