[1] Central Asia is currently a semiarid-arid region, dominated by the Westerlies. It is important to understand mechanisms of climate and precipitation changes here, as water availability in the region is crucial today and in the future. High-resolution, absolutely-dated oxygen isotope (d 18 O) records of stalagmites from Kesang Cave characterize a dynamic precipitation history over most of the past 500,000 years. This record demonstrates, for the first time, that climate change in the region exhibits a processional rhythm with abrupt inceptions of low d18 O speleothem growth at times of high Northern Hemisphere summer insolation followed by gradual d 18O increases that track decreases of insolation. These observations and interpretations contrast with the interpretation of nearby, but higher elevation ice core records. The absolutely-dated cave d18 O shifts can be used to correlate the regional climate variability by providing chronological marks. Combined with other paleoclimate records, the Kesang observations suggest that possible incursions of Asian summer monsoon rainfall or related moisture into the Kesang site and/or adjacent areas during the high insolation times may play an important role in changing orbital-scale hydrology of the region. Based on our record, arid climate will prevail in this region for the next several millennia, providing that anthropogenic effects do not supersede natural processes.

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 This variation is quite similar to that of the Drought/Flooding index archived from Chinese historical documents.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

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.