【摘要】 据年层计数和TIMS U系测年结果 ,建立了南京汤山葫芦洞YT石笋年际精度时间标尺 (1 80 0 0～ 1 40 0 0aB .P .)。除石笋顶部 5mm层段外 ,高分辨率的δ18O、灰度和年层厚度 3种指标在百年尺度上具有相当一致的对应关系 ,表明这 3种指标对气候因素变化响应比较敏感。综合石笋δ18O和本区古植被资料 ,估计末次盛冰期和波令暖期年均温分别达 7℃和1 5℃。石笋揭示的末次盛冰期气候可进一步划分为 4个阶段 :1 ) 1 81 5 0～ 1 6 90 0aB .P .,年均温和洞穴湿度逐步下降 ;2 ) 1 6 90 0～ 1 6 1 0 0aB .P .,年均温和洞穴湿度相对稳定 ,可进一步划分为 3个暖峰和两个冷谷 ;3 ) 1 6 1 0 0～ 1 5 6 0 0aB .P .,年均温快速下降 ,按氧同位素平衡方程计算 ,其冷谷可能接近于 0℃ ,但洞穴湿度比前期下降幅度并不大 ;4) 1 5 6 0 0～ 1 475 0aB .P .,年均温和洞穴湿度比较稳定。这种气候演化的阶段性和突变性与北大西洋地区气候记录可以对比 ,反映极地与东亚季风气候受共同的驱动机制支配。从石笋 4种指标 (δ18O、δ13 C、灰度和年层厚度 )的功率谱图中识别出不同尺度的太阳活动周期成分 ,其中 80aGleissberg周期特别显著 ,表明末次盛冰期边界条件下太阳活动仍是短尺度气候变化的主要驱动力。更多还原

【Abstract】 One stalagmite (No. YT) from Hulu Caveat Tangshan, Nanjing has more than 3 000 visible annual layers consist of alternations of dark and light color calcites. Three 230 Th ages determined with the Thermal Ionazation Mass Spectrometer techniques are well consistent with the layer counting result and then make it possible to establish an annual resolution time series for the dated sequence. Here we use four proxy indicators, δ 18 O, δ 13 C, gray level and annual growth rate to reveal century scale oscillations of east Asian monsoon climate during the LGM. Using some paleo vegetation data, we firstly tested the effects of oxygen isotopic compositions depending on cave temperature between Blling and the LGM periods. A good agreement in cave temperature between the two estimates from isotope geochemistry and vegetation ecology suggests that the oxygen isotopic equilibrium fractionation (-0.24‰/℃) can be applied to reconstruct century scale atmospheric temperature changes. Variations of the gray level along the stalagmite section, as indicated by content changes of impurities in annual bands, are most controlled by fluctuations of humid degree in the cave. The annual growth rate (thickness of annual layer) can be also interpreted as changes of water amounts infiltrated into the cave, which dominated wet and dry conditions in the cave. The cave environment during the LGM, taking all of four proxies of the stalagmite into consideration, can be generally subdivided into several century scale stages as follows: (1) The first two centuries of stalagmite chronology, beginning at 18 150aB.P., was a highest temperature and humidity episode in the extremely cold LGM period. After this warm and humid peak, the temperature and humidity in the cave decreased gradually until 16 900aB.P.; (2) From 16 900 to 16 100aB.P., the cave environment kept a relative stable condition although the stalagmite proxy indicators show three warm peaks and two cold troughs; (3) Synchronizing with the last iceberg event (H1) in the northern Atlantic, one cold event occurred between 16 100aB.P. and 15 600aB.P., with an abrupt cooling pattern, almost reaching 0℃ in mean annual temperature for the first century duration this period. The humidity displayed a negative correlation to variations of temperature during this stage. It may be related to the effective precipitation. The evaporation went up with the increase of temperature, which would reduce the water amounts infiltrated into cave; (4) Similar to the climatic condition of Stage 2, the cave environment maintained a relative stable again for a period from 15 600 to 14 750aB.P. The last time interval of stalagmite chronology is a gradual transition from the LGM to Blling interstadial as reflected by the δ 18 O curve, with a large increase of mean annual temperature (from average 7℃ in LGM to 15℃ in Blling interstadial). Therefore, our data suggest that there existed a climatic tele connection in millennial century time scale between the east Asian monsoon and the North Atlantic atmospheric circulations. We have also detected different time scale cycles of the solar activity, especially Gleissberg cycle of 80 years, from analysis of the Fourier power spectrum for the four stalagmite proxies, supporting the hypothesis that the forcing of the solar activity is a major factor in controlling the Earth climatic system.更多还原