Out-of-phase evolution between summer and winter East Asian monsoons during the Holocene as recorded by Chinese loess deposits |
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| Institution: | 1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an 710075, China;2. Resources & Chemical Laboratory, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Lanzhou 730000, China;1. MOE Key Laboratory of Western China''s Environmental Systems, Collaborative Innovation Centre for Arid Environments and Climate Change, Lanzhou University, Gansu, Lanzhou 730000, China;2. State Key Laboratory of Cryospheric Science, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China;1. Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University, Ottawa, Ontario K1S 5B6, Canada;2. Department of Geography and Environmental Studies, Carleton University, Ottawa, Ontario K1S 5B6, Canada;1. MOE Key Laboratory of Western China’s Environmental Systems, Collaborative Innovation Centre for Arid Environments and Climate Change, Lanzhou University, Lanzhou 73000, China;2. State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China |
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| Abstract: | We analyzed climate proxies from loessic-soil sections of the southern Chinese Loess Plateau. The early Holocene paleosol, S0, is 3.2 m thick and contains six sub-soil units. Co-eval soils from the central Loess Plateau are thinner (~ 1 m). Consequently higher-resolution stratigraphic analyses can be made on our new sections and provide more insight into Holocene temporal variation of the East Asian monsoon. Both summer and winter monsoon evolution signals are recorded in the same sections, enabling the study of phase relationships between the signals. Our analyses consist of (i) measurements of magnetic properties sensitive to the production of fine-grained magnetic minerals which reflect precipitation intensity and summer monsoon strength; and (ii) grain-size analyses which reflect winter monsoon strength. Our results indicate that the Holocene precipitation maximum occurred in the mid-Holocene, ~ 7.8–3.5 cal ka BP, with an arid interval at 6.3–5.3 cal ka BP. The winter monsoon intensity declined to a minimum during 5.0–3.4 cal ka BP. These results suggest that the East Asian summer and winter monsoons were out of phase during the Holocene, possibly due to their different sensitivities to ice and snow coverage at high latitudes and to sea-surface temperature at low latitudes. |
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