基于洞穴钙板碳、氧同位素和Δ47温标的青藏高原东南缘MIS7.2时段气候变化过程与机制探讨  

CLIMATE CHANGE DURING MARINE ISOTOPE STAGE 7.2(MIS7.2) RECORDED BY CARBON,OXYGEN AND CLUMPED ISOTOPE IN CAVE FLOWSTONE FROM SOUTHEASTERN TIBETAN PLATEAU

作　　者：卢淑娴 王芳[1,2] 刘宏[3] 雷国良[1,2,4] 李苗发[1,2] 蔡炳贵 LU Shuxian;WANG Fang;LIU Hong;LEI Guoliang;LI Miaofa;CAI Binggui(School of Geographical Sciences,Fujian Normal University,Fuzhou 350007,Fujian;State Key Laboratory for Subtropical Mountain Ecology of the Ministry of Science and Technology and Fujian Province,Fujian Normal University,Fuzhou 350007,Fujian;International Joint Research Center for Karstology,Yunnan University,Kunming 650223,Yunnan;Institute of Geography,Fujian Normal University,Fuzhou 350007,Fujian)

机构地区：[1]福建师范大学地理科学学院,福建福州350007 [2]福建师范大学湿润亚热带山地生态国家重点实验室培育基地,福建福州350007 [3]云南大学国际喀斯特联合研究中心,云南昆明650223 [4]福建师范大学地理研究所,福建福州350007

出　　处：《第四纪研究》2022年第4期978-990,共13页Quaternary Sciences

基　　金：国家重点研究发展计划项目(批准号:2017YFA0603401);国家自然科学基金项目(批准号:41661144021);福建师范大学校创新团队基金项目(批准号:IRTL1705)共同资助。

摘　　要：本研究基于云南香格里拉石卡雪山高原面洞穴钙板SK下部约8.2 cm厚的7个^(230)Th年龄、81组碳氧同位素和9个Δ47温度数据,恢复了MIS 7.2时段的气候变化历史。SK-δ^(18)O序列重建了213.75~199.74 ka B.P.时段的印度夏季风演变过程,平均分辨率约180 a,该序列显示δ^(18)O值在209.17 ka B.P.和205.00 ka B.P.前后显著正偏,清晰记录了两个千年尺度季风减弱事件。通过与亚洲季风区石笋记录的对比发现,在MIS 7.2开始阶段印度夏季风与东亚夏季风同步变化,但在结束阶段,SK记录早于三宝洞记录约4000 a,考虑到样品年代误差及分辨率等因素,认为该时段轨道尺度上亚洲季风具有一致变化,但是准确时间还有待进一步厘清。Δ47古温度曲线与δ^(18)O、δ^(13)C记录的对比显示出MIS 7.2结束时段水热异步变化特征,与黄土-古土壤序列结论类似,不同的是SK记录的温度直接响应北半球太阳辐照度变化,而不是响应南极温度变化。SK记录显示夏季温度从207.36 ka B.P.左右逐渐回升,同期印度夏季风缓慢增强,但被大幅度的千年尺度季风减弱事件中断,印度夏季风显著增强滞后温度变化约6000 a,该过程与末次消冰期中海因里希事件(Heinrich events)或新仙女木事件(YD)类似,其机制可能与高纬气候变化有关,即冰盖融解导致大量淡水注入北大西洋,影响了北大西洋深水(NADW)和南极底层流(AABW)的生成,从而导致温盐环流(THC)减弱或中断,并通过大气-海洋环流传递到低纬地区,触发千年尺度印度夏季风减弱事件。High-resolution terrestrial climate index over Marine Isotope Stage 7.2(MIS 7.2)could improve our understanding of glacial-interglacial climate change.Speleothem-based record from the East Asian Summer Monsoon(EASM)region has been well reconstructed.In contrast,records with high resolution and well dating constrained from the Indian Summer Monsoon(ISM)domain are still scarce.In this paper,we use carbon(δ^(13)C),oxygen isotope(δ^(18)O)and clumped isotope(Δ47)records of the flowstone to reconstruct the history of climate change during MIS 7.2.The cave(27°48'N,99°36'E;4449 m a.s.l)is located on the plateau of Shika Snow Mountains,Shangri-La City,Yunnan Province,southeastern of Tibetan Plateau.Precipitation of this regional is strongly affected by ISM.Most of precipitation(more than 70%)occurs during summer monsoon season(June to September).Mean annual temperature and precipitation recorded by the Shangri-La meteorological station are 6.3℃and 650 mm(1981~2010).Flowstone SK,105 mm in height,was collected at 5 meters from the entrance of the sinkhole.It's composed of densely pure calcite,with milky white in colour,excepting for top 24 mm.All powder samples were collected on the white and densely part,total about 82 mm.Total of 7^(230)Th dating were performed on MC-ICPMS,and 81 stable isotope were analyzed using MAT 253 coupling with Gasbench-Ⅱ.In addition,9 clumped isotope(Δ47)experiments were determined on a dual injection mode of isotope ratio mass spectrometer(IRMS;Thermo ScientificT M 253 Plus)for paleotemperature reconstruction.The SK-δ^(18)O values vary from-14.93‰to-10.50‰,with an average value being-11.98‰.Its variability is interpreted as the change in the intensity of the Indian summer monsoon.Therefore,the SK-δ^(18)O time series recorded the evolution of the Indian Summer Monsoon with an average resolution of 180 years from 213.75 ka B.P.to 199.74 ka B.P.Two millennial-scale weak monsoon events,centering in 209.17 ka B.P.and 205.00 ka B.P.respectively,can be clearly identified.Compared to t

关 键 词：MIS 7.2 印度夏季风 香格里拉 Δ47 古温度 

分 类 号：P597.2[天文地球—地球化学] P532[天文地球—地质学]