A STALAGMITE-RECORD OF EAST ASIAN SUMMER MONSOON IN THE LAST 2000 YEARS AND ITS CORRELATION WITH HISTORICAL RECORDS

A 4-5 year resolution oxygen isotope record based on 21²³⁰Th dates and 486 oxygen isotope data from a 236-mm-long stalagmite, which was collected from Xi-niu Cave in Shengnongjia, Hubei Province, provides a detailed history of the East Asian Summer Monsoon (EASM) during the past 2000 years. Our δ¹⁸O sequence reveals that EASM intensity gradually weakened in the last 2000 years, superimposed by numerous decades or century-scale aridity/moisture oscillations, showing a characteristics of the typical Medieval Warming Period and Little Ice Age. The δ¹⁸O record generally correlates well with the summer insolation at 33°N, indicating that the long-term trend of the EASM is likely modulated by summer insolation. A comparison with history literatures shows that periods of constant negative δ¹⁸O values (stable moisture periods) occur during the Han and Tang Dynasties, while intervals of positive yet large oscillation in δ¹⁸O values (aridity and abrupt monsoon variability) correspond to the War Era, Song and Ming Dynasties, indicating frequent plagues of aridity/flood. This relationship suggests a clear link between climate change and the demise of these dynasties, and climate variability probably played an important role in Culture evolution.