Penultimate glacial ice and solar radiation affect the hydroclimate of eastern China

There are great uncertainties in the characteristics and dynamics of East Asian monsoon precipitation at the orbital scale, so it has become a hot spot in paleoclimate research. In order to explore this question, Professor Wang Yongjin’s team from Nanjing Normal University published a paper entitled “The Impact of Penultimate Glacial Ice and Solar Radiation on the Hydroclimate of Eastern China” in Science China: Earth Sciences Issue 1, 2023. The study provides a multi-index reconstruction record of a stalagmite in Huludong, Nanjing, eastern China (Figure 1), which mainly reflect the hydroclimatic conditions of the study area. This new evidence suggests that precipitation in eastern China was affected by a combination of ice quantity and solar radiation during the penultimate ice age.

Figure 1 HL163 δ18O, δ13C, Sr/Ca, Mg/Ca and δ234U0 sequences of Hulu travertine stalagmites

(a) Comparison of solar radiation with δ18O sequence in summer (21 July) at 65°N, showing stalagmite dating error; (b)~(e) are δ13C, Sr/Ca, Mg/Ca and δ234U0 sequences, respectively. Blue shaded bars indicate higher values of solar radiation in summer and lower values of stalagmites indicators. The black arrows indicate the trend recorded by the indicator

Clarifying the relationship between East Asian summer wind precipitation, northern hemisphere summer solar radiation and global ice mass is the key to understanding the dynamic mechanism of orbital scale East Asian summer wind change. A large number of geological archives from oceans, loess, lakes and cave stalagmites are widely used to reconstruct the history of summer wind precipitation in East Asia. The northern hemisphere summer solar radiation and Chinese stalagmite δ18O records show a good matching relationship, both showing a significant ~20kyr change period, indicating a strong coupling relationship between them. However, other East Asian summer monsoon indicator records, such as the magnetic susceptibility of the Loess Plateau in China, generally show a more intense ~100kyr cycle, indicating that the East Asian summer monsoon responds to changes in global ice quantity.
Other stalagmite indicators, such as δ13C and trace elements, are less useful in reconstructing paleoclimatic history than stalagmite δ18O indicators. Recent studies have shown that stalagmite delta 13C and trace elements have important potential in reflecting changes in precipitation at cave sites. Based on the multi-index stalagmite records (δ18O, δ13C, Mg/Ca, Sr/Ca and δ234U0) dated to Huludong in eastern China, this paper reconstructs the history of summer wind precipitation in East Asia during the penultimate glacial period. The common variation characteristics of δ13C, Mg/Ca and Sr/Ca sequences are mainly controlled by the hydrological conditions of cave sites, so their first principal component (PC1) can be used as a reliable precipitation index. Precipitation in eastern China gradually decreases during the penultimate glacial period with ice expansion, while precipitation increases during periods of high summer solar radiation in the northern hemisphere (Figure 2). This evidence suggests that ice mass and northern hemisphere summer solar radiation are likely to have an important effect on East Asian summer wind precipitation through westerly wind modulation.

Fig. 2 Comparison of precipitation records in Huludong with solar radiation, ice mass and precipitation records on the Loess Plateau in summer

(a) 65°N summer (21 July) solar radiation; (b) Ice quantity records; (c) Comparison of precipitation records in Huludong and Baoji; (d) Comparison of Huludong and Gulang/Jingyuan precipitation records

The results show that the multi-index reconstruction of stalagmite can effectively obtain the information of summer wind precipitation change in East Asia, and provide new ideas for understanding the characteristics and mechanism of summer wind precipitation change in East Asia at the orbital scale.
Chinese edition: Wang Quan, Yuan Shayue, Liang Yijia, Zhao Kan, Shao Qingfeng, Zhang Zhenqiu, Zhu Junji, Kong Xinggong, Wang Yongjin, Lan Jianghu, Cheng Hai, Xia Chengwei, Li Yi. 2023. Influence of penultimate glacial ice and solar radiation on hydroclimate in eastern China. Science China: Earth Sciences, 53(1): 72–81
English version: Wang Q, Yuan S, Liang Y, Zhao K, Shao Q, Zhang Z, Zhu J, Kong X, Wang Y, Lan J, Cheng H, Xia C, Li Y. 2023. Ice-volume and insolation influences on hydroclimate changes in central eastern China during the antepenultimate glacial period. Science China Earth Sciences, 66(1): 71–79, https://doi.org/10.1007/s11430-021-9979-x
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