The moisture dynamics in arid Central Asia over the last 47,000 years: Insights from the speleothem record.

Abstract

Water resources are crucial for the survival and development of human societies in arid Central Asia. However, our understanding of regional hydroclimate variability and moisture dynamics remains limited. Here, we present a precisely dated, high-resolution speleothem δ18O record from caves in northern Uzbekistan that reconstructs changes in precipitation δ18O over the last 47,000 years. During the glacial interval, relatively low speleothem δ18O values align with precipitation isotope records from high northern latitudes. The close correspondence between the Uzbekistan record and Greenland ice-core δ18O during Heinrich Stadial 1 indicates a strong temperature control on regional precipitation δ18O, although Dansgaard-Oeschger-scale variability is weakly expressed. During the Holocene, speleothem δ18O reached minimum values near 8 ka BP and then increased toward the present, broadly consistent with records from southern Uzbekistan and the Asian monsoon region, but with less coherent centennial- to millennial-scale variability. Supported by model simulations, we propose that during the glacial and mid-Holocene, when winter temperatures were low, the regional precipitation was dominated by northerly and northwesterly moisture transport linked to enhanced high-latitude temperature gradients and southward-shifted westerlies. In contrast, late Holocene hydroclimate increasingly reflected southerly to southwesterly cyclonic moisture transport from the eastern Mediterranean and the Near East, driven by northward-shifted westerlies. These results show that arid Central Asian hydroclimate and precipitation δ18O have been shaped by the position and strength of the westerlies through major reorganizations in moisture-source trajectories, with direct implications for understanding future water availability as subtropical and temperate circulation zones shift northward.