High-resolution stalagmite δ~(18)O records of Asian monsoon changes in central and southern China spanning the MIS 3/2 transition

摘要

High-resolution oxygen isotope records of three stalagmites from Sanbao (central China), Wulu (southern China) and Dashibao (southern China) Caves, based on 876 oxygen isotope measurements and 25 precise ~(230)Th dates, provide a detailed Asian monsoon (AM) history from 32.5 to 20.8kaB.P., spanning the shift between Marine Isotope Stages 3 and 2. The calcite δ~(18)O records, although geographically widespread (about 1000km between them), including the previously-reported Hulu record, are similar in timing, shape, and amplitude. These observations support the idea that changes in speleothem δ~(18)O largely represent variations of precipitation isotopic composition associated with large-scale summer monsoon circulation over a large portion of China. These profiles show four centennial to millennial scale strong summer monsoon events, analogous in timing and structure to Greenland Interstadials 5 through 3 (GIS 5-3). Chronology of the events refines the Hulu record and broadly supports the NGRIP GICC05 timescale. Five weak monsoon events are identified at 31.2, 30.1, 28.1, 25.7 and 24.2kaB.P., all of which correspond to stadial events in Greenland. The 30.1 and 24.2ka events correlate with Heinrich stadials 3 and 2. Furthermore, these events correlate to warm episodes in Antarctic ice cores, indicating that the climatic response to North Atlantic cooling is similar in China and in Antarctica, but in an opposite sense. These observations are consistent with the bi-polar seesaw hypothesis. The strong coupling between AM circulation and climate at both high latitudes at the centennial scale indicates that atmospheric circulation changes are important in transmitting abrupt climate signals globally.