發(fā)布時間：2018-05-21 21:25

  本文選題：冰盛期 + 神秘期��； 參考：《南京師范大學》2015年博士論文

【摘要】：過去50萬年來的高分辨率亞洲石筍6180記錄詳細刻畫了亞洲季風的變化歷史；明確了太陽輻射對季風變化的調控作用及對北半球冰蓋消融的誘發(fā)作用；揭示了北高緯冰蓋變化對千年尺度變化事件發(fā)生頻率和持續(xù)時間的影響；證實了在相對穩(wěn)定的全新世太陽活動是季風百年尺度變率的主控因素；已成為全球氣候對比的基石之一。從末次盛冰期到冰消期再到全新世,地球氣候經歷了從全球冰蓋最大到快速消融再到退縮到最小的三個完全不同的階段。因此,系統地研究這3個階段的氣候變化過程有利于深入理解地球系統內部各要素如冰蓋變化過程、大洋/季風環(huán)流重組與C02氣體變化之間的耦合關系,為評估溫室氣體是否對氣候變化產生影響提供理論依據；提取石筍多元氣候指標有助于了解各氣候要素的響應行為特征和準確理解突變氣候的發(fā)生機制,還有利于評估和驗證頗有爭議的石筍δ180的氣候意義。本文選取貴州省西南區(qū)域的程家春洞石筍同位素和南京葫蘆洞石筍同位素和微量元素變化建立了從冰盛期到晚全新世平均分辨率為5.2 a的亞洲季風演化序列。CJC-1記錄覆蓋的時段為21.5-2.0 ka,δ18O的變化范圍為-6.5‰～-14.5‰,波幅達到8‰；即使在相對穩(wěn)定的全新世,波幅也達到5‰,與現代降水δ180的波幅一致。CJC-1δ18O與其他亞洲石筍記錄的重現性說明CJC-1沉積時同位素達到平衡分餾,可用來重建古氣候變化,較大的δ18O波幅說明對外界氣候變化敏感。在盛冰期～19.5-17.5 ka時段,CJC-1和葫蘆洞石筍都顯示季風強度異常增強,達到B(?)lling-Allerod間冰階水平,不同于盛冰期時季風減弱的模擬結果。此強季風事件與北大西洋溫鹽環(huán)流(AMOC)增強呈對應關系,說明海洋環(huán)流在盛冰期向歐亞大陸輸送的熱量足以引起季風增強。神秘期(17.5-14.5 ka)得名于在該時段內發(fā)生了一系列相互難以解釋的氣候現象。美國西南大湖盆在～16.1 ka由大干旱向大濕潤轉型的原因一直懸而未決。通過對發(fā)育有年紋層的葫蘆洞石筍YT進行刀削法采樣,發(fā)現δ18O在～16.1 ka于20 a內迅速偏正2‰,與ITCZ迅速南移的持續(xù)時間(17 a)相當。表明在～16.1ka發(fā)生的H1a冰漂碎屑事件導致全球水文循環(huán)發(fā)生重組,極地急流南移促使太平洋輸送到美國西南部的水汽增加,從而引發(fā)北美西南大湖盆由大干旱轉向大濕潤。YT石筍的微量元素Sr/Ca和紋層厚度記錄都在16.1 ka發(fā)生明顯轉折,且在百年-數十年尺度上與反映區(qū)域大尺度季風環(huán)流的δ18O記錄有很好的對應關系,進一步支持了MI內部發(fā)生有低緯水文循環(huán)變化的過程和δ18O能夠反映亞洲季風強度的解釋。另一個神秘的氣候事件是大氣△14C在此3000 a的時間內下降幅度達到190±10‰。通過數理分析,我們發(fā)現亞洲季風強度、AMO C、南大洋蛋白石通量、大氣CO2和△14C各記錄在YD和MI兩個時段的相對變化幅度的比值大致相等(～0.5),暗示了冰消期時大氣和大洋環(huán)流的緊密耦合關系,表明AMOC驅動了全球CO2和大氣△14C的變化,引起CO2和△14C變化的碳庫為南大洋。在YD事件內部,CJC-1 δ18O和δ13C記錄的4個百年尺度振蕩與NGRIP冰芯記錄有極好的對應關系。但是,在YD事件開始時CJC-1 δ18O和613C記錄呈現出明顯差異：CJC-1 δ13C與NGRIP δ18O享有相同的結構特征和持續(xù)時間；而CJC-1 δ18O記錄的持續(xù)時間要長于NGRIP δ18O記錄,與其他亞洲石筍δ18O記錄一致。CJC-1 δ13C和NGIRP記錄的對應性有助于避免石筍與冰芯之間的年齡時標差異來評估δ180指示的季風環(huán)流與格陵蘭溫度之間的相位關系。結果表明在YD事件開始時,季風環(huán)流減弱要早于格陵蘭溫度變化,表明YD事件并不是由AMOC變化觸發(fā)的。從YD事件開始,石筍CJC-1 δ13C與NGRIP δ18O、全球冰量變化在長期趨勢上有很好的對應關系。去趨勢后CJC-1δ13C記錄的百年尺度波動與北大西洋IRD以及8.2 ka事件、格陵蘭溫度和太陽活動有明顯的對應性。此對應關系進一步支持了基于董歌洞石筍δ18O記錄得出的北大西洋氣候和太陽活動共同影響全新世東亞氣候的理論,也說明石筍δ18O確實能夠反映季風區(qū)的水文循環(huán)。本研究首次提供了一支從冰盛期到晚全新世長達20 ka的連續(xù)的高分辨率石筍同位素記錄。通過結合南京葫蘆洞石筍記錄,探討了神秘期美國西南部大湖盆由大干旱向大濕潤轉型、大氣C02升高和△14C下降的原因；通過對比CJC-1與格陵蘭同位素記錄,明確地發(fā)現YD事件開始時亞洲季風環(huán)流的減弱過程要早于格陵蘭溫度的下降過程CJC-1 δ13C首次記錄了北大西洋IRD事件,證實了北大西洋氣候在全新世對東亞水文循環(huán)的影響。
[Abstract]:The high resolution Asian stalagmite 6180 records over the past 500 thousand years depicted the history of the Asian monsoon, the regulation of the solar radiation on the monsoon changes and the inducing effect on the melting of the ice cover in the northern hemisphere, and the influence of the change of the ice cover on the occurrence frequency and duration of the Millennium scale change events. The relatively stable Holocene solar activity is the main controlling factor of the Centennial variability of the monsoon. It has become one of the cornerstones of the global climate contrast. From the last glacial to the deglaciation to the Holocene, the earth's climate experienced three completely different stages from the maximum of the global ice cover to the rapid ablation to the minimum. The study of the 3 stages of climate change is beneficial to the understanding of the changes in the internal elements of the earth system, such as the changing process of ice cover, the coupling relationship between the ocean / monsoon circulation and the change of C02 gas, which provides a theoretical basis for assessing whether the greenhouse gases will affect the climate change. The characteristics of the response behavior of the climatic factors and the accurate understanding of the occurrence mechanism of the catastrophic climate are beneficial to the assessment and verification of the climatic significance of the controversial stalagmite delta 180. This paper selects the isotopes of the Stalagmite in the Cheng Jia Chun cave in the southwestern region of Guizhou and the changes of the stalagmite isotopes and trace elements in the Hulu cave of Nanjing from the ice flourishing period to the late brand new period. The period of Asian monsoon evolution sequence.CJC-1 recorded with an average resolution of 5.2 a was 21.5-2.0 Ka, and the range of delta 18O was -6.5 per 1000 to -14.5 per 1000, and the amplitude reached 8 per thousand. Even in the relatively stable Holocene, the amplitude reached 5 per thousand, and the recurrence of.CJC-1 [Delta] 18O and other Asian stalagmite records was consistent with the amplitude of the modern precipitation delta 180. During the deposition of CJC-1, the isotopes reached equilibrium fractionation and can be used to reconstruct the paleoclimate change. The larger Delta 18O amplitude is sensitive to the external climate change. In the period of the peak ice period to 19.5-17.5 Ka, the CJC-1 and the gourd cave stalagmites show the abnormal intensities of the monsoon intensity, reaching the level of the B (?) lling-Allerod, which is different from the model of the weakening of the monsoon during the glacial period. This strong monsoon event has a corresponding relationship with the North Atlantic warm salt circulation (AMOC) enhancement, indicating that the heat transported to Eurasia during the full ice period is enough to cause the monsoon enhancement. The mysterious period (17.5-14.5 KA) is named for a series of unexplained climate phenomena during this period. The Great Lake Basin in the southwest of the United States is 16.1. The reason for the transformation of Ka from great drought to great wetness has been unresolved. By cutting the YT of gourd Stalagmite in the gourd hole, which is developed with annual grain, it is found that delta 18O is quickly 2 per 1000 in ~ 16.1 Ka in 20 A, which is equivalent to the duration of the rapid migration of ITCZ (17 A). It shows that the H1a ice drifting event in 16.1ka causes the global hydrological cycle. The rapid southward migration of polar jets caused the Pacific to transport to the southwest of the United States to increase water vapor, causing the trace elements Sr/Ca and layer thickness of the.YT stalagmite from the great drought to the great humid North America and the 16.1 Ka, and on the scale of the Centennial to the decades to reflect the large scale monsoon circulation in the region. The delta 18O record has a good correspondence, which further supports the process of low latitude hydrological cycle changes in the MI and the interpretation of the Asian monsoon intensity. Another mysterious climate event is that the atmospheric Delta 14C is down to 190 + 10 per thousand within the time of this 3000 a. Through mathematical analysis, we found the Asian monsoon intensity. AMO C, the Southern Ocean opal flux, the ratio of the atmospheric CO2 and delta 14C records to the relative amplitude of the two periods of YD and MI are approximately equal (~ 0.5), suggesting the close coupling relationship between the atmosphere and the ocean circulation during the period of the deglaciation, indicating that AMOC drives the global CO2 and atmospheric Delta 14C changes, and that the carbon Library of CO2 and delta 14C changes is in the South Ocean. Within the D event, the 4 Centennial oscillations of the CJC-1 Delta 18O and delta 13C records have an excellent correspondence with the NGRIP ice core records. However, the CJC-1 Delta 18O and 613C records at the beginning of the YD event show obvious differences: CJC-1 Delta 13C has the same structural characteristics and duration as NGRIP Delta, while the duration of the delta record is longer than that of the YD event. The GRIP Delta 18O record, and the correspondence between the.CJC-1 Delta 13C and NGIRP records consistent with the other Asian stalagmite Delta 18O records, helps to avoid the age time difference between the stalagmite and the ice core to assess the phase relationship between the monsoon circulation and Greenland temperature indicated by delta 180. The result indicates that the weakening of the monsoon circulation at the beginning of the YD event is earlier than Greenland temperature. The degree change indicates that the YD event is not triggered by the change of AMOC. From the beginning of the YD event, the CJC-1 Delta 13C and NGRIP Delta 18O, the global ice change has a good relationship with the long-term trend. After detrending, the 100 year scale fluctuation of the CJC-1 Delta 13C record is obvious to the North Atlantic IRD and 8.2 Ka, Greenland temperature and solar activity. This corresponding relationship further supports the theory that the North Atlantic climate and solar activity have a common influence on the climate of the Holocene in the North Atlantic, which is based on the delta 18O record of Dong song stalagmites. It also indicates that the stalagmite Delta 18O can indeed reflect the hydrological cycle of the monsoon region. This study provides the first time from the glacial to the late Holocene to a 20 Ka continuum. High resolution isotopic records of high resolution stalagmite were recorded. By combining the record of Stalagmite in Nanjing Hulu cave, the causes of the transition from great drought to great wetness in the Great Lake Basin in the southwest of the United States, the increase of atmospheric C02 and the decrease of delta 14C were discussed. By contrasting CJC-1 and Greenland isotopic records, the Asian monsoon circulation was weakened clearly at the beginning of the occurrence of the occurrence of the YD event. CJC-1 Delta 13C, which was first recorded in the North Atlantic IRD event earlier than the decline of Greenland temperature, confirmed the influence of the North Atlantic climate on the hydrological cycle of the East Asia in the Holocene.
【學位授予單位】：南京師范大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：P532

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