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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 This variation is quite similar to that of the Drought/Flooding index archived from Chinese historical documents.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-

The density of a stalagmite (WX42A) from Wanxiang Cave, Wudu County, Gansu Province, China, in the western margin of the Asian summer monsoon region, presents regular fluctuations in different deposition periods during the last deglaciation. Over long timescales, high-precision 230 Th dating and high-resolution stalagmite density data indicate that the density-time series between 17644 a BP and 12758 a BP is quite similar to the stalagmite δ 18 O record which reflects Asian monsoon intensity. Strengthening/weakening (lighter/heavier stalagmite δ 18 O values) of the Asian monsoon is accompanied by increase/decrease in stalagmite density. Over short timescales, decrease in stalagmite density correlates to monsoon-retreat events such as the Inter-Allerød Cold Period (IACP), Older Dryas (OD) and Inter-Bølling Cold Period (IBCP). Generally, this kind of decrease in stalagmite density reflects precipitation decrease with weakening of the Asian monsoon, which in turn slows cave dripwater rate and decreases crystal nuclei, leading to enlargement of calcite crystals, weakened biological activity and decreased soil pCO 2 which increases the abundance of impure detrital materials in stalagmites. However, during the period of large amplitude reduction of precipitation and biological activity which resulted from extreme monsoon-retreat events, temperature variation would dominate fluctuation of stalagmite density. For example, stalagmite density increased suddenly when temperature dropped suddenly in the north Atlantic during Heinrich event 1 (H-1). This may be caused by low seepage water temperature, more dissolved calcium carbonate, compact regular crystals forming under higher supersaturation, leading to the stalagmite increased density. Stalagmite density fluctuation sensitively recorded stalagmite growth history and environment, demonstrating that stalagmite density can be used as a proxy for paleoclimatic research. stalagmite density, Asian monsoon, climate change, Wanxiang Cave, monsoon margin Citation:Zhang D Z, Zhang P Z, Sang W C, et al. Implications of stalagmite density for past climate change: An example from stalagmite growth during the last deglaciation from Wanxiang Cave, western Loess Plateau.

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 δ 18 O dw and δ D dw 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 δ 18 O dw of the cave water and the δ 18 O of the precipitations. Using the measured δ 18 O dw and δ 18 O mc values from the mid-farthest parts from the cave entrance and the carbonate paleotemperature equation, the calculated temperatures range from 8.9 to 12.4 , with the mean value of 10.7 and the temperature calculated at 8 locations in the farthest part of the cave is in the range of 10.1 12.4 , with the mean value of 11.5 , being consistent with the survey value(10.99)in the cave, slightly lower than the mean annual temperature (14.4) 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.