HR: 1340h
AN: PP43A-0614    [Abstracts]
TI: Seasonal $\delta$$^{13}$C Variability in Tree Rings From China: Environmental Regulation And Its Relationship to East Asia Monsoon
AU: * Li, Z
EM: zli@utk.edu
AF: University of Tennessee, 306 G&G Building Department of Earth and Planetary Sciences, Knoxville, TN 37996 United States
AU: Yang, W
EM: ydw@sxmb.gov.cn
AF: Bureau of Meteorology of Shaanxi Province, No.36, Bei Guan Zheng Jie, Xi'an, 710015 China
AU: Mora, C I
EM: cmora@utk.edu
AF: University of Tennessee, 306 G&G Building Department of Earth and Planetary Sciences, Knoxville, TN 37996 United States
AU: Liu, R
EM: rongmoliu@loess.llqug.ac.cn
AF: State Key Lab of Loess and Quaternary Geology, CAS, No.22-2, Xi Ying Road, Xi'an, 710054 China
AB: Carbon isotope analyses of $\alpha$-cellulose from modern tree-rings (A.D.1966 to 1995) sampled along the path of the yearly East Asia monsoon invasion (Shennongjia and Huangling) in China show distinct seasonal variations in $\delta$$^{13}$C of up to 3.0 $\permil$ PDB in a single ring. The seasonal patterns of $\delta$$^{13}$C, as well as the annual $\delta$$^{13}$C values, reveal a negative correlation with relative humidity, suggesting environmental regulation on $\delta$$^{13}$C. Four seasonal $\delta$$^{13}$C patterns of tree rings are classified in this study: late-growing season maximum (pattern I); mid-growing season minimum (pattern II); mid-growing season maximum (pattern III), and early-growing season maximum (pattern IV). Various patterns and amplitudes of seasonal $\delta$$^{13}$C variability concurrently occurring in single tree further support the view of environmental regulation on isotopic compositions. The seasonal $\delta$$^{13}$C patterns exhibit distinct regional characteristics in Huangling and Shennongjia. The tree-rings from Huangling, located in the northwest Chinese loess plateau, show that the more negative $\delta$$^{13}$C values usually appear in latewood (autumn growth). In contrast, negative values predominate in earlywood of tree-rings from Shennongjia, a humid area to the southeast. The change in the relative position of more negative $\delta$$^{13}$C values is considered to be the consequence of seasonal East Asia monsoon precipitation which exhibits a systematic shift in the timing of the rainy season from the southeast coast to the northwest inland of China. Normal seasonal $\delta$$^{13}$C patterns have been identified for both sites. In a normal year of East Asia monsoon activity, the tree-rings show a normal $\delta$$^{13}$C pattern: more negative values appear in latewood from Huangling, where precipitation is greatest in autumn, but in earlywood of tree-rings from Shennongjia, where the rainy season begins earlier in the growing season. Abnormal patterns of seasonal $\delta$$^{13}$C in a single ring may thus reveal abnormal East Asia monsoon activity, including seasonal drought or advancement or delay of the rainy season. This study suggests that seasonal patterns of $\delta$$^{13}$C in tree-rings could be used as a proxy index of seasonal climate variability and reveal abnormal activities of East Asia monsoon.
DE: 0400 Biogeosciences
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting