南京年纹层石笋δ^(18)O记录的冰期气候事件特征  

Timing and Structure of Glacial Climate Events Derived from an Annually-Growth Stalagmite δ^(18)O Record from Hulu Cave,Nanjing

作　　者：吴江滢[1] 邵晓华[1] 汪永进[1] 

机构地区：[1]南京师范大学地理科学学院,江苏南京210097

出　　处：《地理科学》2007年第1期75-80,共6页Scientia Geographica Sinica

基　　金：国家杰出青年科学基金(批准号:40225007);江苏省博士后科研项目资助

摘　　要：根据南京葫芦洞一支石笋高精度230Th年龄及纹层计数建立24~21 ka B.P.时段平均分辨率3年的δ18O季风降水序列,精确标定了IS2事件的发生时间。通过与极地冰芯记录对比,发现G ISP2与石笋时标一致,而GR IP和NGR IP时标在相当事件上偏年轻800~2000年。结合洞内另一支不同时段的石笋年纹层记录,证实东亚季风降水与极地气候在反映气候事件特征上有所不同,季风气候在由干向湿的转型期(包括H2、H1)呈现阶梯式增长特征,其持续时间均超过600年,有可能说明除北大西洋温盐环流外,低纬太平洋海-气耦合也是东亚季风气候的重要触发源。Greenland ice cores provided the most directly and highly resolved records of glacial climate events during the past 120 000 years, but they presented different time scales for these rapid climate events. As we previously reported, precisely-dated and high-resolution cave δ^18O records make it possible to correct the chronologies of Greenland ice cores. Furthermore, annual to decadal-resolved monsoon records would explore a detailed transition pattern for the climate events, providing a crucial test for physical models of abrupt climate events. Here we present such precisely-dated East Asian monsoon record between 24 and 21 ka B. P. , and then discuss a possible forcing mechanism for the climate events during the Last Glacial Maximum. The growth phase for one stalagmite from Hulu Cave, Nanjing, has been precisely dated by thermal ionization mass spectrometry and counting result for continuous annual lamination profile under microscope. A total of 727 sub-samples were scraped off from successive laminations of the polished column and their oxygen isotope composition was measured by MAT-253 mass spectrometry. Based on the ^230Th dates and more than 3000-year-long duration of annual banding sequence, an average 3-year resolution stalagmite δ^18O time series between 24 and 21 ka B. P. has been established. The high resolution oxygen isotope record well reflects the variation of Asian summer monsoon precipitation during the last glacial period, i.e. the more negative value of stalagmite δ^18O, the higher precipitati- on. The stalagmite δ^18O record displays large amplitude from -4.709%o to -8. 709%o in δ^18O value, suggesting that monsoon precipitation changed largely in magnitude even during the Last Glacial Maximum. We recognizes two cycles of wet/dry from this record： one is from 24.0 to 22.1 ka B.P. and the other is from 22.1 to 21.1 ka B.P. Most importantly, shorter-term climatic events are superimposed on the two millennial cycles, coherently linking to the remote climate events, such as Heinrich events i

关 键 词：南京石笋 东亚季风 冰期事件 

分 类 号：P532[天文地球—古生物学与地层学]