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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 10
Clim. Past, 14, 1417-1425, 2018
https://doi.org/10.5194/cp-14-1417-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: The 4.2 ka BP climatic event

Clim. Past, 14, 1417-1425, 2018
https://doi.org/10.5194/cp-14-1417-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Oct 2018

Research article | 11 Oct 2018

The 4.2 ka BP 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
  • 4Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
  • 5Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Abstract. The 4.2kaBP 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 3000cal.yrBP to identify the nature and the associated mechanism of the 4.2kaBP event occurring in the monsoonal region of eastern Asia. Higher sand fraction contents, littoral ostracode abundances, and Chenopodiaceae pollen percentages together with lower mean annual precipitation reveal a significant dry event at the interval of 4210–3840cal.yrBP that could be a regional manifestation of the 4.2kaBP event in the northern margin of the East Asian summer monsoon (EASM). We suggest that the drought would be caused by a 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 production over the source area of the EASM, while the cooling of North Atlantic surface waters could suppress northward migrations of the EASM rain belt, both leading to a weakened EASM and thus decreased rainfall in the northern margin of the EASM.

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Multiple proxies of a sediment core at Hulun Lake in the northern margin of the EASM reveal a prominent dry event at the interval of 4210–3840 cal. yr BP that could be the regional manifestation of the 4.2 ka BP event. Future studies should be focused on the investigation of high-quality, high-resolution proxy records from climatically sensitive and geographically representative regions in order to explore the spatiotemporal pattern of the 4.2 ka BP event and the associated dynamic mechanism.
Multiple proxies of a sediment core at Hulun Lake in the northern margin of the EASM reveal a...
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