Based on 5 high-precision 230 Th dates and 103 stable oxygen isotope ratios (δ 18 O) 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 δ 18 O record with instrumental precipitation data at Wudu in the past 50 years indicates a high parallelism between the two curves, suggesting that the speleothem δ 18 O 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 This variation is quite similar to that of the Drought/Flooding index archived from Chinese historical documents.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. stalagmite from Wanxiang Cave, oxygen isotope, monsoonal strength and precipitation, western Loess Plateau, Asian summer monsoonThe Asian Monsoon (AM) is an important part of global climate system and significantly influences the climate of the AM region via an interaction among the oceanland-atmosphere systems. Previous studies [1][2][3][4] have shown that the variation of ocean-atmosphere systems in the Pacific and Indian oceans at interdecadal and interannual timescales could lead to changes in the AM circulation and associated precipitation at the same timescales. For example, Krishnan and Sugi [1] found that

An oxygen isotope record of a stalagmite from Huanglong Cave in the eastern Qinghai-TibetPlateau dated with 230 Th and 210 Pb methods provides variations of the Asian monsoon with an average resolution of 1 year over the past 50 years. This study shows that the δ 18 O of dripwater in the cave represents the annual mean δ 18 O of local meteoric precipitation and the stalagmites were deposited in isotopic equilibrium. A comparison of the stalagmite δ 18 O record with instrumentally meteorological data indicates that shifts of the δ 18 O are largely controlled by the amount effect of meteoric precipitation conveyed through the southwest monsoon (the Indian monsoon) and less affected by temperature. Therefore, the variations of δ 18 O record reflect the changes in monsoon precipitation on inter-annual time scales under the influence of the southwest monsoon. Like many other stalagmite δ 18 O records in the Asian monsoon regions, the δ 18 O record of the stalagmite from Huanglong Cave also reveals a gradually enriched trend during the past 50 years, i.e. relatively enriched in 18 O. This trend may indicate the decline of the Asian monsoon intensity which is consistent with the decrease of monsoon indices. The weakening of the modern Asian monsoon well matched with the temperature changes in stratosphere, which may illustrate that the weakening of the monsoon mainly results from the lowering of solar radiation. stalagmite, oxygen isotopic composition, Asian monsoon, high-resolution, Qinghai-Tibet PlateauStalagmite record has a much longer time span and reserves integrated information [1] , so it is a valuable supplement archive to records of ice core, loess, lake sediment and peat core, etc [2] . Furthermore, stalagmite is an ideal material for precise U-series dating and yields independent time scales [3] . Therefore, stalagmite has become a major data source for continent paleo-climate reconstruction. Among multi-proxy records in stalagmite including stable carbon/oxygen isotope, trace element and laminae, the stalagmite δ 18 O is the most widely used proxies at present [4] . There are multi-answers in explaining oxygen isotopic compositions of stalagmites from different regions because the shifts of the stalag-