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Based on 5 high-precision 230Th dates and 103 stable oxygen isotope ratios (δ18O) obtained from the top 16 mm of a stalagmite collected from Wanxiang Cave, Wudu, Gansu, variation of monsoonal precipitation in the modern Asian Monsoon (AM) marginal zone over the past 100 years was reconstructed. Comparison of the speleothem δ18O record with instrumental precipitation data at Wudu in the past 50 years indicates a high parallelism between the two curves, suggesting that the speleothem δ18O is a good proxy for the AM strength and associated precipitation, controlled by “amount effect” of the precipitation. Variation of the monsoonal precipitation during the past 100 years can be divided into three stages, increasing from AD 1875 to 1900, then decreasing from AD 1901 to 1946, and increasing again thereafter. This variation is quite similar to that of the Drought/Flooding index archived from Chinese historical documents. This speleothem-derived AM record shows a close association with the Pacific Decadal Oscillation (PDO) between AD 1875 and 1977, with higher monsoonal precipitation corresponding to cold PDO phase and vice versa at decadal timescale. The monsoonal precipitation variation is out of phase with the PDO after AD 1977, probably resulting from the decadal climate jump in the north Pacific occurring at around AD 1976/77. These results demonstrate a strong linkage between the AM and associated precipitation and the Pacific Ocean via ocean/atmosphere interaction. This relationship will aid to forecast future hydrological cycle for the AM monsoon region, and to improve forecasting potential of climatic model with observation data from cave.

This paper presents the stable isotopic compositions from the cave dripwater and actively forming soda straw stalactites collected from Wanxiang Cave, Wudu, Gansu, located on the Qinghai-Tibetan Plateau and Loess Plateau transition zone, China. The δ18Odw and δDdw of dripwater samples in the cave plot directly on the local MWL, constructed by using GNIP data from 3 sites surrounding the cave regions (Lanzhou, Xi’an, and Chengdu), the nearest site to the cave, suggesting that there is a close relationship between the δ18Odw of the cave water and the δ18O of the precipitations. Using the measured δ18Odw and δ18Omc values from the mid-farthest parts from the cave entrance and the carbonate paleotemperature equation, the calculated tem peratures range from 8.9 to 12.4°C, with the mean value of 10.7°C and the temperature calculated at 8 locations in the farthest part of the cave is in the range of 10.1–12.4°C with the mean value of 11.5°C, being consistent with the survey value(10.99°C)in the cave, slightly lower than the mean annual temperature (14.4°C) in Wudu. This suggests that modern speleothems are forming under isotopic equilibrium and their isotopic composition accurately reflects the mean annual temperature at the surface, indicating that the isotopic composition of the modern speleothems records local temperature change with credibility.