Temperature and Summer Monsoon Variability During the Past 500 Ka in China

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This award is for a study of the isotopic composition of stalagmite specimens grown over the past 500,000 years in three caves in China: Buddha Cave south of Xian, Huanglong Cave in northwestern Hunan, and Fengyu Cave south of Guilin. The stalagmites will be dated by TIMS U-series methods to establish precise time frameworks upon which the variations of d18O and d13C are to be examined. In these stalagmites the long-term d18O variations provide the history of temperature changes, with lighter d18O values reflecting colder climate. The d13C record represents vegetation changes, such that warm and dry conditions reduce the C3 /C4 plant ratio, the density of vegetation, and the 13C fractionation for carboxylation in C3 plants, giving rise to heavier d13C values. From the isotopic measurements, the proponents will reconstruct records of the paleotemperature and paleomonsoon variability over the past 500 ka, at 102 -103 year resolutions. The proponents will then compare them with the loess records from Central China and the marine oxygen isotope records, to investigate the response of the winter monsoon to global ice volume change.