Tree-ring δ18O based PDSI reconstruction in the Mt. Tianmu region since 1618 AD and its connection to the East Asian summer monsoon

Abstract

Abstract Previous studies on tree-ring stable oxygen isotopes (δ18O) in the monsoon region of China have rarely involved in variations of the East Asian summer monsoon (EASM) and its rainbelt. In this study, a tree-ring δ18O chronology of Cryptomeria fortune at Mt. Tianmu, located south of the Yangtze River lower reaches, was developed and applied to reconstruct the local June–October Palmer Drought Severity Index (PDSI6–10) during the 1618–2013 AD period. The reconstruction explains 40.5% of the observational PDSI6–10 variances during 1951–2013, captures the actual variation features at both high and low frequencies, largely represents the PDSI6–10 in the middle and lower reach regions of the Yangtze River and further south, and the reconstruction is well-compared with other existing proxies. The reconstruction reveals that the durations of 1620 s–1660 s, 1680 s–1700 s, 1810 s–1830 s, 1850 s, 1900 s–1940 s, and 1960 s were drought periods, while wet durations were 1730 s–1770 s, 1790 s–1800 s, 1860 s–1870 s, 1950 s, and 1980 s–1990 s. Based on the meteorological reanalysis data and new EASM definitions, the reconstructed PDSI6–10 correlates with the meiyu rainbelt precipitation and EASM intensity during May–June, which is when Mt. Tianmu is affected by the EASM rainbelt. The Mt. Tianmu tree-ring δ18O chronology exhibits significantly positive correlations with El Nino–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The relationship of the tree-ring δ18O chronology with the PDO could be due to EASM associations, while it is not clear to explain the mechanism of ENSO connecting to the tree-ring oxygen isotope.