Knowledge Resource Center for Ecological Environment in Arid Area
| 北疆地区树轮稳定氧同位素比率(δ18O)气候意义 | |
| 其他题名 | Climatic Significance of Stable Oxygen (δ18O) in Tree-ring in North Part of Xinjiang Uygur Autonomous Region |
| 徐国保 | |
| 出版年 | 2011 |
| 学位类型 | 博士 |
| 导师 | 秦大河 ; 刘晓宏 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 北疆地区地处我国西北干旱区，降水和温度变化受到西风环流的影响，大气降水主要依靠西风输送。研究这一区域的过去气候变化信息，对于理解区域干旱变化的机制、预测区域干湿变化及指导农业生产等有重要的意义。基于树轮稳定同位素分馏机理和统计模型，树轮氧同位素比率(δ18O)能够较好地记录区域气候变化的信息，是古气候研究中最具潜力的指标之一。本研究选择了中国境内天山山脉东部(哈密地区)、中部(乌鲁木齐河源区)、西部(伊犁地区)和阿尔泰山脉的树木年轮样品，建立年分辨率的树轮δ18O年表序列，在利用近53年(1960-2012年)的器测资料探讨了器测时期北疆地区气候变化特征基础上，分析了树轮δ18O序列中记录的控制因子及其过去气候变化信息。得出以下主要结论： (1)过去53年北疆地区气温和降水的变化在冬半年和夏半年存在一定差异。在1960—2012年期间，北疆地区平均气温呈现整体上升的趋势，冬半年增温幅度大于夏半年。1960—2012年期间，北疆地区冬半年降水在阿勒泰地区和伊犁地区呈现增加趋势，而在中东部地区降水变化微弱，保持不变或是略微减少。北疆地区夏半年降水变化呈现不显著的微弱增加。利用1960-2011年干旱指数(SPEI指数)对北疆地区干旱变化进行研究表明：北疆伊犁地区、阿勒泰地区和哈密地区在冬半年气候趋于偏湿。冬夏半年的变化存在着差异，夏半年整个北疆地区除了阿勒泰地区以外，其他区域都呈现不显著的变干趋势。 (2)对北疆地区建立的4条年分辨率树轮δ18O序列进行了气候响应分析，结果表明在我国干旱半干旱的北疆地区树轮δ18O和区域生长季的温度呈现显著的正相关关系；树轮δ18O和降水、相对湿度具有显著的负相关关系；树轮δ18O和区域干旱指数的负相关关系最强。各采样点和树种的树轮δ18O和气候的响应关系是比较一致的，说明北疆地区树轮δ18O能够较好地反映区域干湿变化的气候信号。 (3)基于树轮δ18O序列重建了哈密地区过去300年的干旱变化历史。重建结果表明，哈密地区20世纪相对较湿，而在21世纪初相对干旱，同时表明夏季天山东部区域在进入21世纪并没有明显的变湿趋势。在长时间尺度上，北大西洋涛动(NAO)对于区域干湿变化有一定的影响，NAO强年，区域相对较湿润，NAO弱年，区域相对较干。同时，厄尔尼诺(ENSO)对于该区域干湿变化也有一定的影响：厄尔尼诺期(ENSO暖事件)，该区域相对偏湿；而在拉尼娜期间(ENSO冷事件)，区域相对偏干。综合树轮碳氧稳定同位素重建了天山中部乌鲁木齐河源区干旱变化历史。乌鲁木齐河源区在1817—1840s、1940s、1960—1980s相对干旱，1960到1990年区域趋于偏湿，这也和其他一些代用资料记录比较一致。该重建同时反映出区域干旱历史变化有10、20和30年准周期。天山西部伊犁地区乌孙山样点树轮δ18O重建过去300年干旱变化历史表明伊犁地区自1710年以来具有显著增湿的趋势，在1886年发生显著的变湿，类似的突变点也出现在1886年德令哈降水序列中。伊犁地区自1880s以来变得湿润，与巴基斯坦北部、德令哈地区、蒙古出现变湿的状况相一致，这可能反映了西风系统影响下的区域干旱变化存在一定共同变化的规律性。 (4)基于四个样点的树轮δ18O序列，利用主成分分析的方法提取了第一主成分，尝试利用树轮δ18O网络资料来获取北疆地区干湿变化的信息。结果表明，北疆地区在1810—1830年表现出明显的干旱特征，且这是区域近200年以来最干旱的时段。北疆地区在1800—1880年整体相对偏干，在整个20世纪，区域气候是相对偏湿，但是在最近10年区域气候状况趋于偏干。北疆地区干湿变化序列具有4、6、和8-10年的周期，这些周期和NAO变化的周期具有一致性；同时利用NAO指数和北疆地区干湿变化序列比较显示二者变化比较一致，说明NAO对北疆地区干湿变化具有重要的影响，且这种影响在过去200年来都是存在的。 |
| 英文摘要 | The variability of precipitation and temperature over the Xinjiang Uygur Autonomous Region, northwestern China is influenced significantly by the westerly circulations. The precipitation is mainly transferred by the westerly. It is important to explore the past climate changes for understanding the mechanism of drought variability, predicting drought events and agriculture management. As one of potential and reliable proxies, δ18O in the tree-ring could record the regional climate signals. In this study, we sampled the tree-ring cores from the east, central and west parts of Tianshan Mountains and from the Altay Mountains in China and then established four annual resolved tree-ring δ18O chronologies. We firstly analyzed the climate change in the Xinjiang Uygur Autonomous Region during the past 53 years (1960-2012) based on the observed meteorological data. After that, we explored the climatic signals recorded in the tree-ring δ18O chronologies, and draw several conclusions as following: (1) The variability of temperature and precipitation was different during the winter half of the year and summer half of the year in the north part of Xinjiang Uygur Autonomous Region. Annual mean air temperature was increased during the period 1960-2012. The rate of air temperature warming in the winter half of the year is higher than that in summer half of the year. During the period of 1960-2012 precipitation in winter half of the year was increasing in the Altay area and Yili area, while precipitation changed a little or a slight decreasing in other regions of north part of Xinjiang province. Precipitation in the summer half of the year was slight increasing without significnat during the past 53 years. We detected the variability of drought in the north part of Xinjiang Uygur Autonomous Region using a standardized precipitation-evapotranspiration index (SPEI). The results indicated that drought variability during summer half of the year and winter half of the year was different. During summer half of the year, climate in the whole north part of Xinjiang Uygur Autonomous Region except for Altay area is drying, while most part of these region is wetting during winter half of the year. The wetting center is located in the Altay region, Yili region and Hami region during winter half of the year. (2) Tree-ring δ18O-climate response analyses showed that the growing season temperature had a positive correlation with tree-ring δ18O variability from the north part of Xinjiang Uygur Autonomous Region, whereas the precipitation and relative humidity had a negative correlation with tree-ring δ18O variability. Tree-ring δ18O was strongly correlated with the drought index. The patterns of the response analyses between tree-ring δ18O and climatic parameters (temperature, precipitation, relative humidity and drought index) were similar among different sites from the north part of Xinjiang Uygur Autonomous Region. Above results indicated that the regional tree-ring δ18O could record the drought variability, to a certain degree, from local to region. (3) Drought history during past 300 years for the Hami area was established. The reconstruction showed that climate in the Hami area was wetter during the 20th century, while it was relative dry during the first decade of the 21st century. The summer climate in the Hami area was not wetting since the 21st century. At the long-term scales, North Atlantic Oscillation (NAO) influenced the drought variability in Hami area. When NAO is in positive phase, climate in the region is wetter, and vice versa. Meanwhile, the ENSO has an impact on regional climate. During El Niño period, the climate in the area was wetter than normal, while during La Niña period, the climate is drier than normal. We reconstructed the drought variability for the source area of the Urumqi River from 1817 to 2008 by combined tree-ring δ13C and δ18O. The dry period o |
| 中文关键词 | 北疆地区 ; 树木年轮 ; δ13C ; δ18O ; 干旱历史 |
| 英文关键词 | North part of the Xinjiang tree-ring δ13C δ18O drought |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286960 |
| 推荐引用方式 GB/T 7714 | 徐国保. 北疆地区树轮稳定氧同位素比率(δ18O)气候意义[D]. 中国科学院大学,2011. |
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