High Resolution Characterization of the Asian Monsoon Climate During MIS 5 and 6, Dongge Cave, China

Speleothem samples from Hulu (eastern China, 32° 30'N, 119° 10'E) and Dongge (southern China, 25° 17'N 108° 5'E) caves provide a nearly continuous record of the Asian monsoon over the last 160 ka. Based on the δ ¹⁸O records of two stalagmites from Dongge Cave (D3 and D4), we have shown that Termination II was an abrupt climatic transition occurring at 129.3 +/- 0.9 ka marking the onset of the Last Interglacial Asian Monsoon (Yuan et al., in review). This earlier work had relatively coarse resolution with Termination II bracketed by a single pair of δ ¹⁸O measurements ∼200 years apart in age, providing an upper limit for the rapidity of the climate transition. The Last Interglacial Asian Monsoon lasted 9.7 +/- 1.1 ky, also ending abruptly (<300 y, limited by sample resolution) at 119.6 +/- 0.6 ka. The full glacial-interglacial amplitude is ∼5%, with the abrupt transitions into and out of the Last Interglacial having a range of approximately 3‰ . Higher resolution isotope sampling (averaging ∼30 y, with ∼10 y resolution over Termination II) from stalagmites D3 and D4 has provided a more detailed account of δ ¹⁸O variations over much of MIS 5 and 6. Precise ²³⁰Th dating has replicated the chronology of the samples within error. The higher resolution data set confirms the timing of Termination II, placing it at 128.9 +/- 0.9 ka, BP. The bulk of this transition ( ∼1.7‰ ) took place within 60 years, with the total range of the transition being ∼3‰ . A major issue is climate stability during interglacial periods. There were some early indications of major instability of the Last Interglacial climate (GRIP members, 1993, Nature 364, 203-207). Whereas our record shows no evidence for instability with glacial-interglacial δ ¹⁸O amplitudes, there is clear evidence for abrupt ∼1‰ shifts with periods on the order of several hundred years during the Last Interglacial (supporting some earlier work, An and Porter, 1997, Geology 25, 603-606). Similar to the features found by Dykoski et al. (this meeting) during the Holocene in the Hulu/Dongge record (see also Bond et al., 2001, Science 294, 2130-2136), these shifts cover approximately « of the amplitude of millennial-scale events during the Last Glacial Period in China (Wang et al., 2001, Science 294, 2345-2348). Thus, it appears that abrupt centennial or millennial-scale changes are a general feature of interglacial periods, albeit with significantly smaller amplitudes than events during glacial periods.