NOAA/WDS Paleoclimatology - Dykoski et al. 2005 Dongge Cave Stalagmite Holocene and Deglacial Oxygen Isotope Data

We present a continuous record of the Asian monsoon over the last 16 ka from d18O measurements of stalagmite calcite. Over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230Th dates. d18O and therefore Asian monsoon intensity generally follows changes in insolation,although changes in d18O are generally accommodated in abrupt shifts in contrast to smoothly varying insolation, indicating that threshold effects may be important. d18O decreased dramatically (~3 per mil) at the start of the Holocene (~11.5 ka) and remained low for ~6 ka. Four positive d18O events centered at 11225±97 yr BP (1.05 per mil), 10880±117 yr BP (1.15 per mil), 9165±75 yr BP (1.4 per mil), and a double event centered at 8260±64 yr BP (1.1 per mil) and 8080±74 yr BP (1.0 per mil) punctuated this period of high monsoon intensity. All four events correlate within error with climate changes in Greenland ice cores. Thus, the relationship between the Asian monsoon and the North Atlantic observed during the glacial period appears to continue into the early Holocene. In addition, three of the four events correlate within error with outburst events from Lake Agassiz. The decline of monsoon intensity in the mid-late Holocene is characterized by an abrupt positive shift in d18O which occurs at 3550±59 yr BP (1.1 per mil in ~100 yr). In addition, the Holocene is punctuated by numerous centennial- and multi-decadal-scale events (amplitudes 0.5 to 1 per mil) up to half the amplitude of the glacial interstadial events seen in the last glacial period. Thus, Holocene centennial and multi-decadal-scale monsoon variability is significant, although not as large as glacial millennial-scale variability. The monsoon shows a strong connection with northern South American hydrological changes related by changes in ITCZ position. Spectral analysis of the d18O record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing. However, there are numerous other significant peaks including peaks at El Nino frequencies (observed for high-resolution portions of the record between 8110 and 8250 yr) which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling Holocene monsoon climate. In addition, for this high-resolution portion, we observe a distinctive biennial oscillation of the Asian monsoon, which has been associated with the Tropospheric Biennial Oscillation (TBO).