| 其他摘要 | Since the formation of the peat is mainly controlled by the climate condition, peat deposition contains a lot of the palaeoclimatical and palaeoenvironmental inforaiation. As one of the best climate information medium, peat deposition has been gradually approved by the research field of palaeoclimate change as other geological record, e.g. ice core, loess, tree ring and sediments of ocean and lake. In recent decade, the point of this study is to pick up the climate change signal information of the Holocene. In the research based on the paleoclimatic information from stable carbon isotopic composition from mixed plant cellulose in Hongyuan peat bog, the remains cellulose of mono-species plant, Carex mulieensis, spanning around 12000 years, has been selected from the same peat bog first time, and the 8 13C of the cellulose has also §een determined. As a high-resolution proxy record for the Indian Ocean summer monsoon, the 8 13C time series of the Carex mulieensis reveal the climate change information of the eastern of the Tibet Plateau as the following: 1. The S 13C time series of the Carex mulieensis cellulose has been considered as a sensitive proxy indicator for the strength of the India Ocean summer monsoon. In the period from 11200 to 11800 cal aBP corresponding to the Younger Dryas, the 8 13C values of the Carex mulieensis are highest, indicating lowest relative humidity and temperature in the Hongyuan site, which can be attributed to the weakest summer monsoon activity. It is clearly shown that the lower age limit of Holocene of the region is 11200 cal aBP (14C age 9900 a BP). From around 11200 cal aBP, the 5 13C values of Carex mulieensis cellulose decrease rapidly which reflects transition from weak to strong activity of the Indian Ocean summer monsoon and the climate of this region became humid and warm. In the early-middle Holocene (around 10800-5500 cal aBP), the 5 13C time series of the Carex mulieensis. show generally a low level which indicates the strong activity of the Indian Ocean summer monsoon though there are 4 abrupt increases of the the 5 3C values of Carex mulieensis cellulose which indicates the lower activity of the monsoon. From around 5500 cal aBP onward, the 8 13C time series of the Carex mulieensis cellulose show increases gradually, which indicates that the strength of the summer monsoon generally tends to gradual decrease in the region, in particular, 4 weak activity of monsoon have been recorded. 2. The nigh abrupt variation events of the Indian Ocean summer monsoon, , recorded by 6 13C time series of the Carex mulieensis cellulose, strongly corresponding to the 9 ice-rafted debris events occurring in the North Atlantic Ocean during the same period . Evidence from the two proxy records indicates the teleconnection between Indian Ocean summer monsoon and North Atlantic climate may be linked to abrupt reorganization of the ocean thermohaline circulation, changing the temperature and moisture gradient over southern subtropical Indian Ocean. 3. Power spectrum analysis of the 6 13C time series of the Carex mulieensis cellulose indicates that there are strongly corresponding climatic change, cycle between Indian Ocean summer monsoon and North Atlantic Ocean. Since there are same corresponding between solar activity and summer monsoon, the influence of the solar activity on the correlation between Indian Ocean summer monsoon and North Atlantic Ocean probably existed. 4. The 5 13C time series of the Carex mulieensis cellulose and mixed plant cellulose have the same tendency in the past 12000 years. Both of them reflect the climate change of post-glacial and indicate there are same responses to the variation of Indian Ocean summer monsoon. Compare to the sensitive response to all of the IRD of Atlantic from 8 13C record of Carex mulieensis cellulose, the mixed plant cellulose does not show the same sensitivity. It could not be confirmed that the sensitivity of mixed plant cellulose that use to reflex the Indian Ocean summer monsoon is lower than that of the Carex mulieensis. Further research need to be carried out to investigate the unclear mechanism. |
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