黔北石笋记录的MIS 5d/5c季风突变过程

Stalagmite-inferred abrupt climate change in the East Asian Monsoon at MIS 5d/5c in northern Guizhou Province

基于黔北三星洞石笋（SX29）9个铀钍年龄和420个氧同位素分析,获得了113.6±0.3-106.2±0.4 ka BP（相对于1950年）10年际分辨率的δ18O时间序列.该石笋δ18O时间序列记录了MIS 5d/5c转换时亚洲夏季风强度变化的突变过程.根据突变过程中间点的年龄确定MIS5d/5c突变时间为108.1±0.3 ka BP.石笋记录对MIS 5d/5c突变时间的精确标定可以作为MIS 5阶段重要的年龄控制点,用以校正南北极冰芯记录和深海沉积记录的时间标尺.季风MIS5d/5c转换阶段也表现为类似过去4个冰消期的2个阶段变化过程：阶段Ⅰ为夏季风较弱时期,而南极温度缓慢上升;阶段Ⅱ为夏季风快速增强时期,与甲烷浓度突变同步,南极温度则上升至最高值.

From nine high-precision 230 Th ages and 420 oxygen isotope data points, a stalagmite from Sanxing Cave in northern Guizhou Province reveals the precipitation history of the Asian Summer Monsoon（ASM） from 113.6±0.3 to 106.2±0.4 ka BP（relative to AD 1950）. The decadal-scale high-resolution δ 18 O record shows an abrupt transitional from Marine Isotope Stage（MIS） 5d to 5c. The stalagmite-inferred time interval of the ASM abrupt transition at MIS 5d/5c is between 108.3 and 107.9 ka BP with a 2σ uncertainty of ±0.3 ka; the mid-point of this transition is 108.1±0.3 ka BP. The well-dated MIS 5d/5c abrupt transition can be used as an age marker for chronological calibration of bipolar ice cores and marine records. The ASM underwent a two-phase process during the transition, similar to those for the last four deglaciations. Phase I involved a weak monsoon stage that lasted for several millennia, concurrent with an Antarctic temperature rise. Phase II was marked by rapid intensification of monsoonal precipitation, synchronous with increasing atmospheric CH4 concentration and high thermal conditions in Antarctica.