Central Asia lies at the convergence between the Mediterranean and Asian monsoon climates, and there is a complex interaction between the westerlies with the monsoon to form the climate of that region and its variability. The region is highly vulnerable to changes in rainfall, highlighting the need to understand the underlying controls. We present a stalagmite-based δ18O record from Kesang Cave in western China, using MC-ICP-MS U-series dating and stable isotope analysis. Stalagmite calcite δ18O largely documents changes in the δ18O of precipitation. δ18O in stalagmites was low during the early and middle Holocene (10.0–3.0 ka BP), and shifted to higher values between 3.0 and 2.0 ka BP. After 2.0 ka BP, δ18O fluctuates with distinct centennial-scale variations. Drawing from results of state-of-the-art atmospheric general circulation model simulations for the preindustrial period and 9 ka BP, we propose that changes in moisture source regions and the wetter climate both contributed to the isotopic depletion of precipitation during the early and middle Holocene. Multiple records from surrounding regions indicate a generally wetter climate during the early and mid- Holocene, supporting our interpretation on the speleothem δ18O. Changes in precipitation seasonality do not appear to be a viable explanation for the observed changes, nor increased penetration of monsoonal moisture to the study site. We speculate that the climatic regime shifted around 3.0–2.0 ka BP towards a drier climate, resulting in temperature having dominant control on precipitation δ18O. The demise of three settlements around 500AD at the margin of Tarim Basin coincided with a period of decreased precipitation and increased temperature that likely affected local water resources, underscoring the potential impact of climate on human habitation in this region.
Bibliographical noteFunding Information:
This work was supported by the Chinese Academy of Sciences (grant XDA05080502, 132B61KYSB20130003), National Natural Science Foundation of China grants (41271229, 41420104008, 41290254), and partly supported by the US National Science Foundation (AGS-1405479 to J.C.H. Chiang, and EAR-1211299 to H. Cheng and R. L. Edwards); and funding from the European Union's Horizon 2020 Research and Innovation programme under the Marie Sk?odowska-Curie grant agreement No 691037 (to S.F.M. Breitenbach). We thank W. Kong for providing the CAM5 simulations used in this study, and acknowledge high-performance computing support for the CAM5 from the Yellowstone cluster (ark:/85065/d7wd3xhc) provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation.
- Asian monsoon
- Central Asia
- Moisture source
- Oxygen isotope
- Precipitation seasonality