Centennial- to millennial-scale monsoon changes since the last deglaciation linked to solar activities and North Atlantic cooling

Xingxing Liu,Youbin Sun,Zhisheng An,Gerrit Lohmann,Jef Vandenberghe,Peng Cheng,Xu Zhang,Evan J Gowan

doi:10.5194/cp-16-315-2020

Abstract

Abstract. Rapid monsoon changes since the last deglaciation remain poorly constrained due to the scarcity of geological archives. Here we present a high-resolution scanning X-ray fluorescence (XRF) analysis of a 13.5 m terrace succession on the western Chinese Loess Plateau (CLP) to infer rapid monsoon changes since the last deglaciation. Our results indicate that Rb∕Sr and Zr∕Rb are sensitive indicators of chemical weathering and wind sorting, respectively, which are further linked to the strength of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM). During the last deglaciation, two cold intervals of the Heinrich event 1 and Younger Dryas were characterized by intensified winter monsoon and weakened summer monsoon. The EAWM gradually weakened at the beginning of the Holocene, while the EASM remained steady till 9.9 ka and then grew stronger. Both the EASM and EAWM intensities were relatively weak during the Middle Holocene, indicating a mid-Holocene climatic optimum. Rb∕Sr and Zr∕Rb exhibit an antiphase relationship between the summer and winter monsoon changes on a centennial timescale during 16–1 ka. Comparison of these monsoon changes with solar activity and North Atlantic cooling events reveals that both factors can lead to abrupt changes on a centennial timescale in the Early Holocene. During the Late Holocene, North Atlantic cooling became the major forcing of centennial monsoon events.

Highlights

The East Asian monsoon (EAM) is one of the most important atmospheric circulation systems linked to climate changes over high- and low-latitude regions of the Northern Hemisphere (Ding, 1994)
Our results indicate that Rb/Sr and Zr/Rb are sensitive indicators of chemical weathering and wind sorting, respectively, which are further linked to the strength of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM)
Compared with other summer monsoon proxy records in China, the centennial-scale EASM changes at DDW are consistent with the PANN reconstructed from Gonghai Lake (Fig. 3d) (Chen et al, 2015; Liu et al, 2015, 2017) and summer monsoon index (SMI) from Lake Qinghai (Fig. 3e) (An et al, 2012)

Summary

Introduction

The East Asian monsoon (EAM) is one of the most important atmospheric circulation systems linked to climate changes over high- and low-latitude regions of the Northern Hemisphere (Ding, 1994). It consists of summer and winter monsoons (EASM and EAWM) with significantly seasonal changes in moisture transportation and wind direction. Liu et al.: Centennial- to millennial-scale monsoon changes since the last deglaciation rine sediments (Huang et al, 2011) and model simulations (Wen et al, 2016) These previous studies show a series of oscillations and/or abrupt events, such as the 4.2, 8.2, 9.2 and 10.3 ka events. These records suggest the summer monsoon variations are induced by changes in Northern Hemisphere summer insolation and strongly modulated by internal land–ocean–air interactions of the Earth–climate systems (e.g., An et al, 2015)

Methods

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Discussion

Conclusion