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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 8 | Copyright
Clim. Past, 11, 1067-1075, 2015
https://doi.org/10.5194/cp-11-1067-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 25 Aug 2015

Research article | 25 Aug 2015

Multiscale monsoon variability during the last two climatic cycles revealed by spectral signals in Chinese loess and speleothem records

Y. Li1, N. Su2,3, L. Liang1, L. Ma1, Y. Yan1, and Y. Sun1 Y. Li et al.
  • 1State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, Shaanxi 710061, China
  • 2College of Science, Technology and Engineering, James Cook University, Cairns, Queensland 4870, Australia
  • 3School of Mathematics and System Science, Shenyang Normal University, Shenyang, Liaoning 110034, China

Abstract. The East Asian Monsoon (EAM) exhibits a significant variability on timescales ranging from tectonic to centennial as inferred from loess, speleothem and marine records. However, the relative contributions and plausible driving forces of the monsoon variability at different timescales remain controversial. Here, we spectrally explore time series of loess grain size and speleothem δ18O records and decompose the two proxies into intrinsic components using the empirical mode decomposition method. Spectral results of these two proxies display clear glacial and orbital periodicities corresponding to ice volume and solar cycles, and evident millennial signals which are in pace with Heinrich rhythm and Dansgaard–Oeschger (DO) cycles. Five intrinsic components are parsed out from loess grain size and six intrinsic components from speleothem δ18O records. Combined signals are correlated further with possible driving factors including the ice volume, insolation and North Atlantic cooling from a linear point of view. The relative contributions of components differ significantly between loess grain size and speleothem δ18O records. Coexistence of glacial and orbital components in the loess grain size implies that both ice volume and insolation have distinctive impacts on the winter monsoon variability, in contrast to the predominant precessional impact on the speleothem δ18O variability. Moreover, the millennial components are evident in loess grain size and speleothem δ18O records with variances of 13 and 17 %, respectively. A comparison of the millennial-scale signals of these two proxies reveals that abrupt changes in the winter and summer monsoons over the last 260 kyr share common features and similar driving forces linked to high-latitude Northern Hemisphere climate.

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Multiscale signals were decomposed from Chinese loess and speleothem records over the last 260 kyr. We found great glacial and orbital impacts on the loess grain size changes and dominant precession forcing in the speleothem δ18O variability. The millennial components are evident in the loess and speleothem proxies with variances of 13 and 17%. Close matches of millennial monsoon events between these two proxies indicate similar driving force linked to high-latitude Northern Hemisphere climate.
Multiscale signals were decomposed from Chinese loess and speleothem records over the last 260...
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