On November 29, 2023, the official journal of the American Geophysical Union (AGU), Geophysical Research Letters, published online the latest research findings on paleoclimate reconstruction by professor Li Tingyong and his team from the School of Geography at Yunnan Normal University and the Key Laboratory of Plateau Geomorphic Processes and Environmental Change in Yunnan Province.
While it is well known that global changes have led to variations in the intensity and spatial distribution of Asian monsoon precipitation, the mechanisms behind this are not well understood. Paleoclimate records are essential for revealing the drivers behind monsoon variation. However, speleothem records from the Asian monsoon region rarely provide direct information on the amount of rainfall. Here we report on multiple indicator data sets from a stalagmite in southwestern China. It could help explore the variation of monsoon precipitation over the last ∼100,000 years. We find that the increase/decrease of Northern Hemisphere summer insolation controls the increase/decrease of Asian summer monsoon rainfall. In addition, global ice volume moderates the magnitude of rainfall response to insolation, and precipitation decreases significantly during high ice volume periods. Based on the present paleo-precipitation records evidence, the existence of the spatial pattern of increasing/decreasing rainfall in central China corresponding to decreasing/increasing rainfall in northern and southern China remains ambiguous on the orbital scales, although the feature has been captured by some of the model simulations.
Comparison of the YZ1 X/Ca records with paleoclimate records from different regions of China
Influence of NHSI and ice sheet dynamics on ASM precipitation.
During the modern and Holocene periods, precipitation in the monsoon region of China exhibits a "three-pole" spatial pattern characterized by opposite phases between Central China and the combined regions of Southern and Northern China. However, the reconstruction results from this study indicate that on orbital scales, the precipitation patterns are generally consistent with those in northern and southern China, where a wet hydrological environment corresponds to enhanced Northern Hemisphere Summer Insolation (NHSI) or sea-ice thickness in the Greenland Ice Sheet (SITIG). This suggests that the "three-pole" precipitation pattern in the monsoon region of China on orbital scales remains ambiguous, despite being highlighted by some model simulations. Therefore, when discussing the spatial distribution of precipitation in China's monsoon region based on single reconstruction records at orbital scales, caution should be exercised in interpreting their broader implications.
During the Last Glacial Maximum (LGM), the reduction in summer monsoon precipitation exceeded the decline in Asian Summer Monsoon (ASM) intensity. This indicates that, in addition to Northern Hemisphere Summer Insolation (NHSI) and sea-ice thickness in the Greenland Ice Sheet (SITIG), global ice volume modulated the magnitude of the ASM precipitation response to insolation changes. Stalagmite δ18O primarily reflects the dynamic characteristics of the ASM, such as intensity variations, but caution is warranted when using it for precipitation reconstruction. This study provides a new reference for reconstructing precipitation patterns in China's monsoon region and offers a clearer comparison of the relationship between ASM intensity and regional hydrological conditions.
