Holocene hydroclimate changes on the north‐eastern Tibetan Plateau inferred from geochemical records in Lake Gyaring

Abstract

The north-eastern Tibetan Plateau (TP) is an ideal region for understanding the interaction between the Asian Summer Monsoon (ASM) and the Westerlies. Here we present a high-resolution elemental record from Lake Gyaring in the source region of the Yellow River to investigate the paleo-hydroclimate changes over the past ~10 ka. Our results show that lithogenic elements (Ti, Rb, Mn, Ti, Zn and Ni) increased while carbonate-related elements (Ca, Sr and Mg) decreased up the core sediments, indicating that the effective moisture on the north-eastern TP has steadily increased throughout the Holocene. This inference is also supported by the gradual augmentation and diminution of Rb/Sr and Ca/(Ti + Fe + Al) ratios, respectively. The persistent wetting trend on the north-eastern TP inferred from our study disagrees with the Holocene pattern of the ASM but corresponds well with that of the Westerlies. This implies that the strengthening Westerlies since the Holocene might have played a more important role than monsoon circulation in controlling the hydroclimate changes on the north-eastern TP. However, the significant increase in the mid-Holocene might be related to the combined effects of the strengthened ASM and Westerlies. Ultimately, Northern Hemisphere solar insolation and the substantial remnant of ice sheets might have controlled Holocene moisture availability on the north-eastern TP through their influence on the intensity of the Westerlies and ASM as well as Atlantic Ocean sea surface temperatures.

Sedimentary Black Carbon Isotope Record of Holocene Climate Changes on the Northeastern Tibetan Plateau

“…Ning et al. (2022) have also obtained a persistent wetting trend based on the geochemical results from the same sediment core (Figure 3c). Synthesis of the paleoclimate records from multiple proxies in Lake Gyaring indicates that climate on northeastern TP has shifted from warm and dry to cold and wet over the Holocene.…”

“…Similar climatic variations during the Holocene have also been suggested by the decreasing trend of the particle size and the δ 13 C org values from the same sediment core (Zhao et al, 2021; Figures 3b and 3d). Ning et al (2022) have also obtained a persistent wetting trend based on the geochemical results from the same sediment core (Figure 3c). Synthesis of the paleoclimate records from multiple proxies in Lake Gyaring indicates that climate on northeastern TP has shifted from warm and dry to cold and wet over the Holocene.…”

“…Prior studies have extensively investigated the sources of BC over the TP (Kang et al, 2020;Li et al, 2016;Neupane et al, 2019). Though the source-diagnostic Δ 14 C/δ 13 C compositions of the BC isolated from aerosol (Zhao et al, 2021), (c) Ti concentration (Ning et al, 2022), and (d) grain size variation of the sediments (Zhao et al, 2021). and snowpit samples indicated that the relative contributions from fossil fuel (indicating human resources) and biomass combustion (natural origins) to current BC deposits in the modern times are equal.…”

“…The major atmospheric circulations, including Indian Summer Monsoon, East Asian Summer Monsoon, and the westerlies, are also present by blue, black, and pink arrows, respectively. This figure is modified from Ning et al (2022).…”

“…Comparison of the analysis results of different proxies from the core ZLH2015-1. (a) Stable carbon isotope composition of Black Carbon (δ 13 C BC ) (this study), (b) stable carbon isotope composition of organic matter (δ 13 C org )(Zhao et al, 2021), (c) Ti concentration(Ning et al, 2022), and (d) grain size variation of the sediments(Zhao et al, 2021).…”