The use of stalagmites in the study of the history of the Asian monsoon system

The Asian monsoon consists of three closely linked system, the Indian monsoon (South Asian monsoon), the Southeast Asia monsoon, and, the East Asian monsoon. The Asian monsoon impacts the life of over half the world's population and it is the focus of numerous international efforts to improve our understanding of the Asian monsoon, a history of monsoon variability, and thus improve the ability to model and predict monsoon variability.A detail record of variability of the Asian monsoon system is preserved in the calcium carbonate that makes up stalagmites. Stalagmite bearing caves are present along the regions of greatest precipitation intensity, from north central Nepal, through Bhutan, Myanmar, (Burma), southeastern China, Thailand, Laos, and Vietnam. Annual to seasonal (peak monsoon vs. dry inter-monsoon) growth records of these monsoon systems are preserved by: 1) Changes in the morphology of calcite (fibrous vs. non-fibrous, or. inclusion rich vs. dense) formed by relatively fast drip rates of the peak monsoon vs. the slow drip regime of the dry inter-monsoon; 2) The oxygen isotopic composition of calcite, which is directly linked to changes in precipitation oxygen isotopic composition and reflect amount effects during peak-monsoon 3) Changes in mineralogy (calcite vs. aragonite) or alternating calcite and aragonite layers in stalagmites formed in caves underlying dolomite. These changes result from changes in infiltration intensity and cave desiccation. Calcite is formed during intense monsoon period, and aragonite grows during the dry inter-monsoon or during periods of greatly reduced monsoon intensity 4) Inter-monsoon growth hiatuses recording growth cessation in either caves with thin rock cover and fast infiltration or time periods that have experience major decreases in inter-monsoon precipitation. 5) Mechanical/chemical solution pits produced by extreme fast drip rates of undersaturated fluids during the most intense monsoon periods, or in caves with thin rock cover and fast infiltration. Specific examples from caves in Nepal, Myanmar, and northern Vietnam will be presented.