Tree-ring δ18O in southwestern China linked to variations in regional cloud cover and tropical sea surface temperature

In this paper, we present the first annual oxygen isotope (8180) record (1902 to 2004) from the latewood cellulose of trees growing in a temperate-moist forest in southwestern China. Tree-ring delta O-18 ranges from 12.8 to 18.6 parts per thousand and averages 15.2 parts per thousand. delta O-18 in the latewood negatively correlates with total cloud cover, relative humidity, and precipitation during the moist months (August to October) from 1951 to 2004 and, to a lesser extent, positively correlates with the temperature in June. Spatial correlation analysis revealed that tree-ring latewood delta O-18 is more strongly related to variability in regional cloud cover and precipitation in autumn. Tree-ring delta O-18 negatively correlates with the indices of the Indian summer monsoon (1948 to 2004), the western North Pacific monsoon (1948 to 2004), and with the East Asian summer monsoon (1902 to 2000), suggesting that these monsoons strongly influence the regional climate. Under global warming of last century, we found a strong inverse correlation between tree-ring delta O-18 and the Southern Oscillation index in different periods, indicating a complex association between the El Nino-Southern Oscillation and the regional climate, which in turn affects tree-ring delta O-18. Correlation with the global sea surface temperature (SST) indicates that climatic conditions in the Indian Ocean might play a dominant role in modulating cloud cover and precipitation over the study region during the monsoon seasons. We also found a significant correlation between tree-ring delta O-18 and SST over the western-north Pacific Ocean. Our results suggest strong links between tropical oceans and an ENSO-like climate with the oxygen-isotope sources and discrimination for trees in the study region. (C) 2011 Elsevier B.V. All rights reserved.