Carbon Isotope Record Of High Accuracy Stalagmite In Hubei Shennongjia In Late Holocene

The reconstruction of paleoclimate and paleoenvironment based on speleothem is paid more and more attention, and has obtained many significant achievements. Among all the available climatic indexes, the most common one is stable oxygen isotope (818O). However, the interpretation of its climatic significane is still questioned,which requires other indexes (δ13C, gray level, trace elements, layer thickness, etc.) to enrich paleoclimate study. In view of this, here a high resolution time series for the successive4295years (118-4413a BP) is reconstructed on the basis of32high-precision U/Th dating ages and1864oxygen and carbon isotopic data derived from three stalagmites (BF4, BF1, SN) in Xiniu cave in Hubei Province, central China.The long-term trend of Xiniu cave δ18O record follows the summer insolation at33°N, but the δ13C record shows no significant long-term trend. Variations in the δ13C values are mainly controlled by the soil CO2productivity caused by biomass and microbial activity, and reflect the local climate conditions. The higher δ13C value of Xiniu cave correspond to the warm and humid climate, and the lower813C value may indicate cold-dry climate.The Xiniu cave δ13C clearly recorded the late Holocene climate changes in Hubei, and is rather sensitive to the Little Ice Age. Relatively, the Little Ice Age started later (AD1520) with the broad characteristics of cold-dry/warm-humid cycles. The medieval warm period had a longer duration.The variation in513C records is well consistent with the PDO index on decadal to centennial scales, presenting a negative correlation between them. The strong correlation indicates that the PDO has important influence on the East Asian summer monsoon precipitation.Global climate change is caused by a combination of internal and external forcing factors, and the sun is the most important one. Our data imply that solar radiation and volcanic activity may affect sea surface temperatures firstly, and then the regional climate through ocean currents and/or atmospheric circulations. The power spectral analysis of the three stalagmites δ13C records shows significant periodicities of quasi-66,59,57,41,39and37-36years. I found that the periodicities of66,59and57years are approximately consistent with50-70-year oscillations related with the solar activity and30—40-year cycles are associated with the drought index in eastern China.