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ABSTRACT A speleothem record from south-western China characterizes in detail the millennial-scale changes in Asian Monsoon (AM) intensity from 39.3 to 28.7 ka. The calcite δ18O profile, with an average resolution of ∼8 years, shows several strong monsoon events concurrent with Greenland Interstadials (GIS) 8-4. To gain a systematic perspective of AM millennial-scale variability, the new and previously reported data from the same cave are combined, showing that AM variation exhibits a broad similarity with Greenland ice δ18O records and with Antarctica but in an opposite sense. For the interval that encompasses GIS 5 and GIS 4.1, however, our stalagmite δ18O record depicts a sustained strong monsoon with no distinctive oscillation between these interstadials. Another prominent characteristic in our record is a gradual transition into Chinese Interstadial (CIS) 8, which is well constrained by an annually laminated sequence. We find that an initial rise in monsoon intensity, lasting a few centuries, significantly precedes the abrupt onset of CIS 8 in the AM realm. This suggests that atmospheric moisture and heat transport are probably capable of inducing abrupt climate change when a rapid reorganization of ocean/atmosphere circulations passes a tipping point. [ABSTRACT FROM AUTHOR]

Knowledge of the evolution of pedogenic processes in the carbonate area is important to understand the dynamics of rock desertification. A precisely-dated stalagmite δC record between 61.3 and 50.5 ka BP from southwestern China, potentially related to soil biogenic CO production, shifts within a narrow range between −9‰ and −7‰, and exhibits a prominent cycle of 350-470 a, independent of the Asian monsoon changes. This indicates that a threshold effect might control the amplitude of calcite δC variability, likely associated with the vertical soil loss in the carbonate area. The periodic δC changes reflect that the loss/recovery of soil cover can operate on centennial scale. Thus, the rock desertification in southwestern China might at least initiate 60 ka ago and should be of natural origin. [ABSTRACT FROM AUTHOR]

Based on TIMS U-series dating results and annual band counting method, an annual-resolution time scale from 17450 to 14420 aBP has been established for a stalagmite from the Hulu Cave at Tangshan, Nanjing. A high-resolution oxygen isotopic record reveals decadral-centural oscillations in air temperature in the East Asian monsoon climate area during the last glacial maximum. The most conspicuous feature in the oxygen isotopic record in the period is the particular cold event synchronized with the last Heinrich event (H1) in the northern Atlantic deep-sea records. This particular cold event, beginning at 16140 ± 100 aBP, shows a rapid cooling down with a magnitude of 7–8°C in air temperature within 36 years. Furthermore, δ18O record demonstrates that the event lasted 790 years with gradually warming tendency (10 cycles of air temperature oscillations) after the remarkable cooling down. We believed that this unique pattern of event recorded in the stalagmite δ8O might be controlled by various factors including changes of insolation at mid-latitude Northern Hemisphere, the southern extend of the last ice-rafted event in the North Atlantic and changes of the Equatorial Pacific sea surface temperature. [ABSTRACT FROM AUTHOR]

Abstract: 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 230Th 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 δ18O 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 δ18O 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. [ABSTRACT FROM AUTHOR]