中国中部全新世气候变化的泥炭同位素记录--以湖北神农架大九湖为例

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	中国中部全新世气候变化的泥炭同位素记录--以湖北神农架大九湖为例
其他题名	High Resolution Stable Isotope Record of the Holocene Climatic Variation from Peat Cellulose, Dajiu Lake, Shennongjia,
	洪冰
	2009-05-29
学位授予单位	中国科学院地球化学研究所
学位授予地点	地球化学研究所
学位名称	博士
关键词	全新世大九湖泥炭植物纤维素碳稳定同位素氧稳定同位素温度东亚季风气候突变融冰洪水太阳活动
摘要	泥炭作为一种地质档案，其发育形成过程中包含了丰富的古气候和古环境的变化信息。由于泥炭沉积中植物残体的碳、氧等稳定同位素组成与气候变化之间存在着密切关系，其稳定同位素时间序列已作为气候变化的代用指标逐渐用于古气候的恢复和重建，尤其是在以高时间分辨率重建全新世以来的气候环境变化方面已取得一些重要进展。本论文通过对湖北省神农架地区大九湖泥炭中植物残体的氧、碳同位素的研究，同时以温度和湿度这两种重要的气候参数代用指标，恢复和重建全新世以来中国中部地区的气候状况。通过本论文的工作并与其它相关成果综合对比研究，对从末次冰消期晚期和全新世以来中国中部地区气候状况有如下的认识： 1. 末次冰消期晚期至全新世阶段，大九湖泥炭纤维素δ18O敏感地记录了发生在约14.67～12.89 cal. kaBP的BA暖期以及在此期间所发生的两次冷事件：Oder Dryas冷事件和Intra-Allerød冷事件；并指示随后的Allerød暖期明显较Bølling暖期偏冷；在新仙女木时期（YD），神农架地区温度较低，事件中后期温度开始回升；在11.0～9.0 cal. kaBP的早全新世时期，大九湖泥炭δ18O在波动中升高，指示了整体上的温暖气候，期间存在一系列的气候变冷事件。这些冷事件基本都是叠加在一种长期的、相对较暖的变化趋势上，有别于末次冰消期的突然变冷事件；在9.0～5.0 cal. kaBP的中全新世阶段，神农架地区总体上处于相对温暖的适宜阶段，但波动较为频繁，期间记录到了著名的“8.2ka”冷事件；约5.0 cal. kaBP开始，大九湖泥炭δ18O值持续升高，指示以一次快速的升温过程开始了晚全新世阶段并保持在一个相对较高的温度水平；在整体温暖的气候背景下也明显记录有“4.2ka”、“小冰期”等全球性冷事件；大九湖泥炭纤维素δ18O所记录的温度变化趋势与中国大陆地区其他一些气候代用指标所记录的温度变化趋势有很好的相似性，说明中国大陆地区温度变化的趋势基本一致。 2. 大九湖泥炭δ18O温度变化序列所记录到的历次突然气候变冷事件，与格陵兰冰芯和北大西洋冷事件的发生具有很好的一致性，这说明对应于北半球高纬度区域的气候变化，在中低纬度的中国地区同样存在响应和变化，并且这种响应贯穿于整个全新世阶段。 3. 大九湖泥炭纤维素δ13C敏感地记录了末次冰消期以来东亚季风的演变历史。东亚季风在整个末次冰消期至晚全新世阶段始终处于一种强弱交替的波动态势。在末次冰消期至全新世早期，其整体上表现为一种由弱转强的态势；在全新世早期和中期阶段，东亚季风活动强度整体较高，表现为整个时间序列中的高活动时段，而其中也出现了数次明显的减弱迹象；全新世晚期阶段，东亚季风的活动强度较中期和早期为弱，整体上表现出低幅的波动但没有恢复到前两个时期的活动强度。在中世纪温暖期阶段的中后期，东亚季风的活动强度开始在波动中逐渐升高。 4. 该泥炭纤维素代用指标所记录的一些东亚季风突变（增强）事件与同一时期所发生的印度季风的突变（减弱）事件具有很好的对应关系；进一步证实这两个季风系统之间所存在的反相变化关系；同时，这些突变事件与北大西洋IRD冷事件在发生时间段也具有较好的对应关系，即每当北大西洋地区气候变冷时，东亚季风都表现出增强的迹象。 5. 综合分析中国泥炭同位素古气候记录和其它研究结果，对气候驱动机制有如下认识：当太阳活动发生百年至千年时间尺度的减弱时，由大气臭氧层变化所触发的影响向大气层下部延伸，导致北半球气候变冷；同时，减弱的太阳活动可能在赤道太平洋触发类厄尔尼诺状态出现，并引发印度洋夏季风减弱和东亚夏季风增强；早全新世北半球冰盖周围大冰湖冰岸坍塌，湖中巨量体积淡水突然流入北大西洋，导致海洋温盐环流传送带运转放慢甚致停顿，通过跨赤道的温盐环流向北输送的热量大大减少，引起北半球气候变冷；由于海洋温盐环流的变化改变了全球热量的分配，暖水在地球南部积累，导致西太平洋暖池区域海表面水与深层水温度之间反差的增加，从而有利于类厄尔尼诺状态出现，同样将可能引起印度洋夏季风减弱和东亚夏季风增强。
其他摘要	As an independent geological archive, peat deposition contains a lot of paleoclimatic and paleoenvironmental information during its development and formation. The stable isotope, such as carbon and oxygen in the plant residue of the peat has a close relationship with past climatic change. In this connection, the time series of its stable isotope has been used to restore and rebuild paleoclimate as a proxy indicator for paleoclimatic change. In particular, important progress has been made in the climatic and environmental change since reconstruction of the Holocene with high resolution. Based on the research on oxygen and carbon isotope of plant residue in the peat at the Dajiu Lake in Shennongjia, Hubei Province, we rebuild the climatic conditions in Central China for the first time since the last deglaciation by two climatic parameters, temperature and humidity synchronously. In comparison with other related researches and achievements, the understanding about the climatic conditions in Central China since the late deglaciation and the Holocene goes as follows: 1. From the last deglaciation to the Holocene, the peat cellulous δ18O of the Dajiu Lake has sensitively recorded BA warming period at around 14.67～12.89 cal. kaBP and two cooling events, Oder Dryas and Intra-Allerød, in this period. Meanwhile, it indicated clearly that the subsequent Allerød warming period was colder than the Bølling warming period. At the Younger Dryas (YD), the temperature in Shennongjia was rather low and it bottomed out in the middle and late of the event. Early Holocene at around 11.0～9.0 cal. kaBP, the peat δ18O at the Dajiu Lake rose in fluctuation, which indicated the warm climate of the whole. In this period, there were a series of cooling events superimposed onto the variation trend of long-term but relatively warm climate, which are different from the abrupt cooling event in the last deglaciation. In the middle of Holocene at 9.0～5.0 cal. kaBP, it remained warm in Shennongjia with frequent fluctuation. It recorded the famous “8.2ka” cooling event occurring in this period. Starting approximately from 5.0 cal. kaBP, the peat δ18O value at the Dajiu Lake rose consecutively, which indicates there was a rapid temperature rise, announcing the beginning of the late Holocene and the temperature remained on a high level. In the background of overall warm climate, it also recorded global cooling events such as “4.2ka” and “Little Ice Age” etc. The temperature variation trend recorded by peat cellulous δ18O at the Dajiu Lake was quite similar to that recorded by the other proxy records in Chinese Mainland, which indicates that the trend of temperature variation in Chinese Mainland accords more or less. Meanwhile, some events of temperature anomaly recorded by peat cellulous δ18O are also occurred in some other areas of China. 2. The abrupt cooling events recorded in the peat δ18O at the Dajiu Lake were in good accordance with those occurred in the ice core of the Greenland and the North Atlantic. These cooling events show that the repeatedly occurring temperature cooling pattern not only appeared in the North Atlantic Region in the high latitudes, but also in the Northwest Pacific Region in the middle latitudes. Furthermore, this response came throughout the whole Holocene Epoch. 3. The peat cellulous δ13C at the Dajiu Lake had sensitively recorded the variation history of the East Asian Monsoon since the last deglaciation. From the last deglaciation to the Holocene, East Asian Monsoon was consistently in an alternation of strong and weak. From the last deglaciation to the early Holocene, the whole tendency was from weak to strong; from early Holocene to its middle, the activity of East Asian Monsoon increased and strengthened as a whole, which represented as high activity period in the whole temporal sequence. In this course, however, East Asian Monsoon also fell off obviously a few times. In the late Holocene, the intensity of East Asian Monsoon was weaker than that of the middle and the early of the Holocene. As a whole, it represented as a low fluctuation extent but it did not return to the intensity of the first two periods. In the middle and late of the Medieval Warm Period, East Asian Monsoon began to increase gradually in fluctuation. 4. Some abrupt change (strengthening) events of the East Asian Monsoon recorded by the peat cellulous of the Dajiu Lake were corresponded well with the abrupt change (weakening) events of the Indian Monsoon in the same period, which further confirmed an anti-phase of the these two monsoons system. Meanwhile, these abrupt events occurred in the period also correspond to that happened during the IRD cooling events at North Atlantic in terms of the occurrence time. That is to say, when it became cold in the North Atlantic region, the intensity of East Asian Monsoon would strengthen. 5. According to the comprehensive assessment record of the ancient climate peat isotopes in China and other research achievements, the understanding of the climate driving mechanism goes as follows: when the decreased solar activity on centennial to millennial scales occurred, the influence triggered by the change of the atmospheric ozone layer spreads to the lower part of the atmosphere which led the cold change of the climate in the Northern Hemisphere. Meanwhile, the decreased solar activity may cause El Niño on the equator-Pacific and the weaken Indian Monsoon and stronger East Asian Monsoon. The ice bank of the great ice lake around the ice sheet collapsed in the early Holocene, catastrophic meltwater discharge into the North Atlantic may have triggered the conveyor belt of the thermohaline circulation slowed down or even stopped its motion. The heat conveyed to the north through the thermohaline circulation across the equator decreased substantially, which cooled the climate of the Northern Hemisphere. At the same time, the change of oceanic thermohaline circulation alters the global thermal distribution, so the warm water accumulated in the south of the earth and the difference between. the temperature of the surface water and that of the deep water in the warm-pool area of Western Pacific increased, which was facilitate to the occurrence of El Niño as well as weaken the Indian Monsoon and stronger the East Asian Monsoon.
页数	121
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3466
专题	研究生_研究生_学位论文环境地球化学国家重点实验室
推荐引用方式 GB/T 7714	洪冰. 中国中部全新世气候变化的泥炭同位素记录--以湖北神农架大九湖为例[D]. 地球化学研究所. 中国科学院地球化学研究所,2009.

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