高分辨率石笋记录的三峡库区小冰期气候变化

Climate Change During Little Ice Age with High-resolution Stalagmite Record in the Three-Gorges Reservoir Area

基于重庆水鸣洞石笋（NSM03）7个^230Th年代数据和438个δ^18O数据建立三峡库区1250～1750A．D．时段分辨率约为1a的δ^18O记录。分析显示石笋δ^18O值在1280A．D．开始迅速偏重，在1300A．D．附近偏到近500a来最重，显示季风迅速减弱，库区进入小冰期。石笋记录显示小冰期存在明显的年代际尺度干湿波动，特别是在1400～1650A．D．时段石笋δ^18O值高频振荡，显示季风降水处于频繁波动期。功率谱分析显示石笋δ^18O序列具有显著树轮△14^C周期和ENSO准周期，揭示太阳活动是小冰期主要驱动因素，同时受到海气耦合作用影响。

A high-resolution oxygen isotope profile of the past 500 years was established with an average resolution of approximately one year, based on 7 high-precision^ 230Th dates and 438 stable oxygen isotope ratios （δ^18O） which were obtained from a stalagmite （NSM03） collected from Shuiming Cave, Chongqing City. So the variation of summer monsoon precipitation in the Three-Gorges reservoir area during the period of 1250-1750 A.D. was reconstructed. The δ^18O value of the stalagmite NSM03 became heavier rapidly from 1280 A.D., and reached to the heaviest around 1300 A.D. During the past 500 years, the Asian monsoon became weak rapidly, implying the Little Ice Age （LIA） starts. The trend of δ^18O record from stalagmite NSM03 coincides with the other stalagmite records of the Asian monsoon region within the limits of dating error. Results showed that there were obvious interdecadal wet and dry fluctuations in LIA, especially during 1400-1650A.D.δ^18Ovalue of the stalagmite fluctuated dramatically indicating that monsoon precipitation was in frequently fluctuate period. Spectral analysis showed NSM03 δ^18O sequence had significant cycle of 98, 26, 5, 4, and 3 years （above the 99% confidence level）. Similar periodicities of 98 and 26 years were proved by the δ^18O record, further supporting the idea that solar changes were mainly responsible for Asian monsoori intensity changes in LIA; and 5, 4 and 3 years were consistent with the 2-7 years standard cycle of E1 Nino-Southern Oscillation （ENSO）, which implied that LIA climate variation had a close relation with ENSO.