Millennial-scale climate variability has not been well documented in arid northwest China due to the scarcity of high-resolution, well-dated paleoclimate records. Here we present multi-proxy records from sediment cores taken in freshwater Hurleg Lake on the northeastern Tibetan Plateau, which reveal millennial-scale lake-level and climate variations over the past 8,000 years. This high-elevation region is very sensitive to large-scale climate change, thus allowing us to better understand Holocene climate variations in East Asia. The lake-level record, derived from lithology, magnetic mineralogy, carbonate isotopes, ostracode shell isotopes and trace elements, X-ray fluorescence (XRF), and gray scale data, indicates a highly variable and generally dry climate from 7.8 to 1 ka (1 ka = 1,000 cal year BP), and a relatively stable and wet climate after 1 ka. Superimposed on this general trend, six dry intervals at 7.6-7.2 ka, 6.2-5.9 ka, 5.3-4.9 ka, 4.4-3.8 ka, 2.7-2.4 ka, and 1.7-1.1 ka were detected from the high-resolution carbonate content and XRF data. The generally dry climate between 7.8 and 1 ka was almost synchronous with the decrease of East Asian and Indian monsoon intensities shortly after 8 ka. The six dry intervals can be correlated with weak monsoon events recorded in the East Asia and Indian monsoon regions, as well as the North Atlantic cold events. Our data suggest that millennial-scale monsoon variations could cause highly variable climate conditions in arid northwest China during the Holocene. These millennial-scale climate variations may reflect changes in solar variation and/or changes in oceanic and atmospheric circulation.
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Acknowledgments We thank Jixiu Cao, Aifeng Zhou, Xiuju Liu and Ke Zhang of Lanzhou University for field coring assistance, Eric Brown of the University of Minnesota, Duluth for XRF analysis, the Keck-CCAMS facility of University of California, Irvine for radiocarbon dating, the staff at LacCore (National Lacustrine Core Facility) of the University of Minnesota for initial core description and subsampling, and two anonymous reviewers for comments. The project was supported by the Chinese NSF and US NSF. This is Contribution 10-03 of the Limnological Research Center of the University of Minnesota.
- Asian monsoon
- Millennial-scale moisture variations
- Tibetan Plateau