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

Abstract Speleothem oxygen isotope (δ18Os) record as a climatic proxy in southeastern China is still in debate due to multifaceted influencing factors, a modern δ18Os record, which can be calibrated or compared with observational data, is critical to explore the interpretation of δ18Os proxy. Here we present a seasonally resolved δ18Os record spanning the interval of 1898–2018 CE from Niubi Cave, Guangdong Province, southeastern China. A comparison between the Niubi δ18Os and instrumental data reveals that the Niubi δ18Os variability is primarily controlled by changes in precipitation seasonality modulated by El Nino-Southern Oscillation on interannual to interdecadal timescales. Higher (lower) δ18Os values correspond to lower (higher) ratios of the East Asian summer monsoon/non-summer monsoon precipitation during the El Nino (La Nina) 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 δ18Os values over the last 120 years, the rest of drought events associate with the negative δ18Os 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 δ18Os 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.