A 120-year seasonally resolved speleothem record of precipitation seasonality from southeastern China

Speleothem oxygen isotope (δ¹⁸O_s) record as a climatic proxy in southeastern China is still in debate due to multifaceted influencing factors, a modern δ¹⁸O_s record, which can be calibrated or compared with observational data, is critical to explore the interpretation of δ¹⁸O_s proxy. Here we present a seasonally resolved δ¹⁸O_s record spanning the interval of 1898–2018 CE from Niubi Cave, Guangdong Province, southeastern China. A comparison between the Niubi δ¹⁸O_s and instrumental data reveals that the Niubi δ¹⁸O_s variability is primarily controlled by changes in precipitation seasonality modulated by El Niño-Southern Oscillation on interannual to interdecadal timescales. Higher (lower) δ¹⁸O_s values correspond to lower (higher) ratios of the East Asian summer monsoon/non-summer monsoon precipitation during the El Niño (La Niña) events associated with concomitant changes in the outgoing longwave radiation, wind field and Western Pacific Subtropical High. While ∼73% historical drought events correlate to positive anomalies in Niubi δ¹⁸O_s values over the last 120 years, the rest of drought events associate with the negative δ¹⁸O_s anomalies. This observation suggests two different mechanisms for the drought events with more and less diminution of rainfall amount in the East Asian summer monsoon relative to the non-summer monsoon precipitation, respectively. Additionally, our Niubi δ¹⁸O_s record from southeastern China, together with other high-resolution speleothem and tree ring records, demonstrate a “tripole pattern” of summer precipitation during the last ∼100 years in eastern China.