pubmed.ncbi.nlm.nih.gov

Loess deposits in the low latitudes of East Asia reveal the ~20-kyr precipitation cycle - PubMed

  • ️Mon Jan 01 2024

Loess deposits in the low latitudes of East Asia reveal the ~20-kyr precipitation cycle

Xusheng Li et al. Nat Commun. 2024.

Abstract

The cycle of precipitation change is key to understanding the driving mechanism of the East Asian summer monsoon (EASM). However, the dominant cycles of EASM precipitation revealed by different proxy indicators are inconsistent, leading to the "Chinese 100 kyr problem". In this study, we examine a high-resolution, approximately 350,000-year record from a low-latitude loess profile in China. Our analyses show that variations in the ratio of dithionite-citrate-bicarbonate extractable iron to total iron are dominated by the ~20-kyr cycle, reflecting changes in precipitation. In contrast, magnetic susceptibility varies with the ~100-kyr cycle and may be mainly controlled by temperature-induced redox processes or precipitation-induced signal smoothing. Our results suggest that changes in the EASM, as indicated by precipitation in this region, are mainly forced by precession-dominated insolation variations, and that precipitation and temperature may have varied with different cycles over the past ~350,000 years.

© 2024. The Author(s).

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Map showing the East Asian summer monsoon (EASM), the East Asian winter monsoon (EAWM), and the Indian summer monsoon (ISM).

The dashed green lines represent the modern Asian summer monsoon (ASM) limit. The triangles represent the locations of the study (red) and reference (black) sites. A digital elevation model (SRTM V4) used in the figure is available from the CGIAR-CSI SRTM 90 m Database (

http://srtm.csi.cgiar.org

).

Fig. 2
Fig. 2. Comparison of magnetic susceptibility curves between the Madang and Luochuan profiles.

The tie points (red dots) are linked by dashed blue lines. The yellow diamonds represent the depths of the optically stimulated luminescence (OSL) samples. The OSL ages for samples at each depth are also shown.

Fig. 3
Fig. 3. Wavelet and spectral analysis results for the low-latitude loess records.

a Wavelet analysis of magnetic susceptibility. b Spectral analysis of magnetic susceptibility. c Wavelet analysis of FeD/FeT. d Spectral analysis of FeD/FeT.

Fig. 4
Fig. 4. Correlation analysis of the Madang records and other curves.

a Magnetic susceptibility from Madang vs. an Antarctic temperature proxy, δD. b Magnetic susceptibility from Madang vs. benthic δ18O record from the LR04 stack. c FeD/FeT from Madang vs. stalagmite δ18O record from Sanbao Cave. d FeD/FeT from Madang vs. insolation difference between 30° N and 30° S in July.

Fig. 5
Fig. 5. Comparison of the FeD/FeT record from this study with other proxy and forcing time series.

a Wet–dry record from Chahanchi Lake in the Tengger Desert. b Spliced East Asian summer monsoon record from Xijin loess drill cores on the western Chinese Loess Plateau. c FeD/FeT record from Madang. d Insolation difference between 30° N and 30° S in July. The vertical bars indicate intervals of low summer insolation, which generally correspond to periods of low precipitation in both the monsoon core zone (Madang) and the monsoon marginal zone (Chahanchi Lake and Xijin).

Similar articles

References

    1. Ding Y, Chan JCL. The East Asian summer monsoon: an overview. Meteorol. Atmos. Phys. 2005;89:117–142. doi: 10.1007/s00703-005-0125-z. - DOI
    1. Cheng H. Orbital-scale Asian summer monsoon variations: paradox and exploration. Sci. China Earth Sci. 2021;64:529–544. doi: 10.1007/s11430-020-9720-y. - DOI
    1. An Z, et al. The long-term paleomonsoon variation recorded by the loess-paleosol sequence in central China. Quat. Int. 1990;7–8:91–95.
    1. An Z, et al. Magnetic susceptibility evidence of monsoon variation on the Loess Plateau of central China during the last 130,000 years. Quat. Res. 1991;36:29–36. doi: 10.1016/0033-5894(91)90015-W. - DOI
    1. Ding Z, et al. A coupled environmental system formed at about 2.5 Ma in East Asia. Palaeogeogr. Palaeoclimatol. Palaeoecol. 1992;94:223–242. doi: 10.1016/0031-0182(92)90120-T. - DOI