Climatic change during the last 4000 years in the southern Tarim Basin, Xinjiang, northwest China

In this study, a ca. 4000 cal. yr ancient lacustrine (or wetland) sediment record at the southern margin of Tarim Basin is used to reconstruct the history of climate change. Six radiocarbon dates on organic matter were obtained. 618 0 and delta C-13 of carbonate, pollen and sediment particle size were analysed for climate proxies. The proxies indicate that a drier climate prevailed in the area before ca. 1010 BC and during period 1010 BC-AD 500 climate then changed rapidly and continuously from dry to moist, but after about AD 500 climate generally shows dry condition. Several centennial-scale climatic events were revealed, with the wettest spell during AD 450-550, and a relatively wetter interval between AD 930-1030. Pollen results show that regional climate may influence human agricultural activities. Spectral analysis of mean grain size (MGS) proxy reveals statistically pronounced cyclic signals, such as ca. 200 yr, ca. 120 yr, ca. 90 yr, ca. 45 yr and ca. 33 or 30 yr, which maybe associated with solar activities, implying that solar variability plays an important role in the decadal- and centennial-scale climate variations in the study area. Copyright (C) 2007 John Wiley & Sons, Ltd.