Isotopic evidence in modern precipitation for the westerly meridional movement in Central Asia

The seasonal and inter-annual variations of stable isotopes in alpine precipitation in arid Central Asia is of great help to understand the modern hydrological processes and climate proxy in the westerly-dominant region. In this study, we measured the 3-year precipitation isotope values at a site located on the southern Tianshan Mountains in Central Asia. The delta O-18 values of precipitation show a statistically significant relationship with air temperature (R-2 = 0.58). The trajectory diagnostics indicate the strong influence of westerly moisture, although the local trajectories do exist. According to the 3-year isotope records in the sampling site, the delta O-18 values of precipitation correlated with the meridional circulation index, while the correlation with the zonal circulation index is generally weak. An isotope-enabled GCM is used to analyze the correlation between the delta O-18 values in summer precipitation and the meridional and zonal wind speeds on a longer time scale; there is a strong correlation between the delta O-18 values and the meridional wind speed for the upwind direction. The findings indicate the meridional movement of mid-latitude westerly can be sensitively recorded in the modern precipitation in arid Central Asia, and the inter-annual variability of precipitation isotopes in Central Asia can not only be attributed to temperature effect.

Automated summary

This study examined the 3-year precipitation isotope values at a site located on the southern Tianshan Mountains in Central Asia, showing a significant relationship between delta O-18 values of precipitation and air temperature, as well as the Meridional circulation index. The findings suggest that the movement of mid-latitude westerly can be sensitively recorded in modern precipitation in arid Central Asia.