Tree-ring δ18O from Southeast China reveals monsoon precipitation and ENSO variability

Abstract Considerable advances have been made in use of tree-ring δ18O for climate reconstructions in Southeast China, the East Asian summer monsoon region. However, the relationships among tree-ring cellulose δ18O (δ18Ocell), local hydroclimate, precipitation δ18O (δ18Opre) and El Nino–Southern Oscillation (ENSO) have not yet been fully resolved. The usual interpretation has been that local hydroclimate influences δ18Ocell through both the “amount effect” on δ18Opre and evaporative enrichment, but it cannot fully explain the high inter-site correlation of δ18Ocell chronologies or their response pattern to ENSO. In this study, we use a newly-developed δ18Ocell chronology of Pinus massoniana from a water-stressed site in Zhejiang province, in combination with another three δ18Ocell chronologies in Southeast China, to investigate their climatic implications from a regional perspective. The results show that besides local hydroclimate, δ18Opre is also significantly correlated with δ18Ocell, but with different effects. Spatially homogeneous δ18Opre variation causes high spatial correlations among δ18Ocell from different sites. Analyses show that ENSO variations are responsible for the large-scale common signals in δ18Ocell by modulating δ18Opre. Therefore, combining δ18Ocell chronologies from different locations can enhance ENSO signals, which provides us new opportunities to reconstruct paleo-ENSO activities. Furthermore, eliminating the part of ENSO signal that is not related to the growing season hydroclimate from δ18Ocell can increase the explained variance of observed values. These findings provide a guide for future optimized ENSO and local paleoclimate reconstructions using δ18Ocell.