Regional hydroclimate and precipitation delta O-18 revealed in tree-ring cellulose delta O-18 from different tree species in semi-arid Northern China

Oxygen isotopic ratios (delta(18)O) of tree-ring cellulose, grown from 1954 to 2003 in semi-arid Northern China demonstrate a common inter-annual variability, despite coming from three different species in two distinct growth environments (an alpine meadow and a rocky ridge). The variability was significantly negative correlated with precipitation and relative humidity during the growing season. This suggests that the past summer hydroclimate can be inferred from tree-ring cellulose delta(18)O from various kinds of trees growing in semi-arid Northern China. In addition, we evaluated past changes in delta(18)O of precipitation from the tree-ring cellulose delta(18)O and relative humidity using the mechanistic model for tree-ring cellulose delta(18)O in Roden et al. (2000). By fixing the species-dependent exchange rate of oxygen between carbohydrate and xylem water for Larix principis-rupprechtii and Picea koraiensis, we could also reconstruct the variations in precipitation delta(18)O from the different tree species, which are similar to the observed delta(18)O of precipitation during 1985-2002. Although the reconstructed delta(18)O of precipitation does not have any significant relation to local temperature or precipitation during 1954-2003, its long-term variation pattern is similar to that of the Asian summer monsoon indices and delta(18)O of stalagmite in the Heshang cave (30 degrees 27&#39;N, 110 degrees 25&#39;E; Fig. 1), suggesting that delta(18)O of precipitation is not controlled by local meteorology but is influenced by large-scale atmospheric circulation.</p

Hydroclimate variability in the North China Plain and its link with El Nino-Southern Oscillation since 1784 AD: Insights from tree-ring cellulose delta(18)O

We present here a chronology of tree-ring cellulose delta(18)O from 1784 to 2003 that is based on the individual measurements of five Larix principis-rupprechtii trees growing in the semiarid North China Plain (NCP; 34 degrees-41 degrees N, 107 degrees-120 degrees E). This chronology has a significant, negative correlation with summer precipitation, relative humidity, and the Palmer Drought Severity Index. It is representative of regional summer hydroclimate variability in the NCP by analyzing its spatial correlation patterns with CRU TS3 precipitation grid data sets. Historically, extreme climate events (drought and flood) could be detected by the high-frequency (annual) signals in the chronology. The low-frequency (11 year moving average) signals are consistent with the time series of the drought frequency and the regional dryness-wetness index derived from historical documents in the NCP. Significant spatial correlation patterns of measured precipitation and the tree-ring cellulose delta(18)O chronology from the NCP with observed sea surface temperature in the eastern equatorial Pacific during the 1954-2003 and 1854-2003 periods suggest that the summer hydroclimate of the NCP has a close link with El Nino-Southern Oscillation. Mostly extreme dry or wet years identified by the chronology follow historical El Nino or La Nina events over the past 220 years, respectively.</p

Plant-wax hydrogen isotopic evidence for postglacial variations in delivery of precipitation in the monsoon domain of China

The Asian monsoon is a key component of the Earth&#39;s climate system that directly affects the livelihood of 60% of the world population. Reliable reconstruction of changes in monsoon precipitation during the Holocene is required to better understand the present climate conditions and to predict future climate processes in the Asian monsoon domain. Reconstruction of changes in Holocene monsoon precipitation has been done in various regions of this domain using a variety of paleoclimate proxies. However, different proxies have yielded different paleoclimate records of long-term monsoon rainfall variability. We apply compound-specific stable hydrogen isotope compositions of the plant wax n-alkanes isolated from the Hongyuan peat sequence in eastern Tibet to reevaluate the regional carbonate oxygen isotopic and lake-level records. The D/H ratios of the n-alkanes resolve the apparent discrepancy among the different paleoclimate proxies. Our result indicates that lake-level fluctuation is a reliable recorder of changes in the amount of summer monsoonal precipitation while long-term isotope records largely reflect large-scale changes in the source of water vapor rather than a local precipitation signal. Combining lake-level, biomarker, and carbonate isotopic records, we conclude that the early Holocene monsoon precipitation in southwest China has been greatly influenced by the Indian monsoon.</p