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

Résumé fourni par la source

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 δ 18 O record from caves in northern Uzbekistan that reconstructs changes in precipitation δ 18 O over the last 47,000 years. During the glacial interval, relatively low speleothem δ 18 O values align with precipitation isotope records from high northern latitudes. The close correspondence between the Uzbekistan record and Greenland ice-core δ 18 O during Heinrich Stadial 1 indicates a strong temperature control on regional precipitation δ 18 O, although Dansgaard-Oeschger-scale variability is weakly expressed. During the Holocene, speleothem δ 18 O 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 δ 18 O 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.

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