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Discussion papers | Copyright
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 18 Jun 2018

Research article | 18 Jun 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).

The 4.2 ka event: multi-proxy records from a closed lake in the northern margin of the East Asian summer monsoon

Jule Xiao1,2,3, Shengrui Zhang1, Jiawei Fan1, Ruilin Wen1,2, Dayou Zhai4, Zhiping Tian5, and Dabang Jiang5 Jule Xiao et al.
  • 1CAS Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
  • 2CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China
  • 3College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
  • 4School of Resources, Environment and Geosciences, Yunnan University, Kunming 650091, China
  • 5Nansen–Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Abstract. The 4.2ka event has been widely investigated since it was suggested to be a possible cause for the collapse of ancient civilizations. With the growth of proxy records for decades, however, both its nature and its spatial pattern have become controversial. Here we examined multi-proxy data of the grain-size distribution, ostracode assemblage, pollen assemblage and the pollen-reconstructed mean annual precipitation from a sediment core at Hulun Lake in northeastern Inner Mongolia spanning the period between 5000 and 3000calyrBP to identify the nature and the associated mechanism of the 4.2ka event occurring in the monsoonal region of eastern Asia. Higher sand fraction contents, littoral ostracodes abundances and Chenopodiaceae pollen percentages together with lower mean annual precipitations reveal a significant dry event at the interval of 4230–3820calyrBP that could be a regional manifestation of the 4.2ka event in the northern margin of the East Asian summer monsoon (EASM). We suggest that the drought would be caused by a large decline in the intensity of the EASM on millennial-to-centennial scales that could be physically related to persistent cooling of surface waters in the western tropical Pacific and the North Atlantic. The cooling of western tropical Pacific surface waters could reduce moisture productions over the source area of the EASM, while the cooling of North Atlantic surface waters could suppress northward migrations of the EASM rainbelt, both leading to a weakened EASM and thus decreased rainfall in the northern margin of the EASM.

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