EVOLUTION AND ABRUPT CHANGES OF THE HOLOCENE ASIAN MONSOON CLIMATE RECORDED BY STALAGMITE IN BAIGU CAVE IN GUIZHOU

A Holocene speleothem δ¹⁸O time series was reconstructed based on 390 stable isotope data and 13 ²³⁰Th dates, covering a period from 12.8 to 3.3 kaBP. This record, with an average decadal-scale resolution, well reflects Asian summer monsoon history and thus its precipitation. A long-term trend of stalagmite δ¹⁸O profile bears a high similarity to the summer insolation at 33°N, suggesting that changes in solar irradiation forced the Holocene monsoon circulation during the entire Holocene period. We identified three stages from the stalagmite δ¹⁸O record, i.e. a transition of YD/Holocene at about 11ka, a humid stage during 10.5~5.8 kaBP and a gradually decreased monsoon precipitation stage since 5.8 kaBP. During the early Holocene,stalagmite δ¹⁸O record of an average 37-year resolution correlates well with the Greenland temperature record. Firstly, the two records show a similar detailed internal oscillation in YD event and abrupt changes out of YD event. Secondly, during the transition of YD event/Holocene period, three stepwise stages can be recognized in both of the records. Such coherence may suggest that the abrupt climate events in Northern Hemisphere were triggered by the coupled tropical ocean-atmosphere. During 7.0~3.3 kaBP, the stalagmite δ¹⁸O record, with a resolution of 15 years, displays a centennial-scale variability of monsoon precipitation. Among these, five weak monsoon events with a pace of 500~1000 years, can be related to, within the uncertainty of U/Th dates, five cold events recorded in Greenland ice core respectively. The inherent link between the high and low latitude climates can, in part, be ascribed to responses to changes of solar activity.