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学科主题: 地理学::自然地理学
题名: 青藏高原纳木错流域水中氧稳定同位素特征研究
作者: 徐彦伟
答辩日期: 2007
导师: 周石硚 ; 康世昌
专业: 自然地理学
授予单位: 中国科学院研究生院
授予地点: 北京
学位: 硕士
关键词: 降水 ; 河水 ; 湖水 ; 稳定同位素 ; 青藏高原 ; 纳木错流域
索取号: S000001
摘要: 目前的全球气候变暖直接影响人类生存环境,研究地球气候环境的变化过程具有重要的现实意义。纳木错流域位于青藏高原的中部,湖泊沉积和现代山地冰川发育,是古气候环境研究的理想场所。而研究水体中氧稳定同位素的变化特征,能为揭示该流域冰芯和湖芯中氧稳定同位素的气候学意义提供重要依据。 本论文根据在纳木错流域采集的多种水体样品中氧稳定同位素比率的测定结果,分析了纳木错流域水体中δ18O的时空特征,揭示了纳木错流域夏、秋季节降水中δ18O与水汽来源及温度的关系,并结合湖泊水量平衡数据,对纳木错湖水中氧稳定同位素的演变过程进行了模拟。研究的主要内容和结果如下: 1)纳木错流域夏、秋季节降水中δ18O变幅较大,不同的水汽来源是决定降水中δ18O变化的主要因素。根据降水气团的不同,把纳木错流域夏、秋季节降水事件划分为海洋性降水和大陆性降水,两种降水中δ18O变化分别与气温有一定的正相关关系,降水时的气温可能是降水中δ18O变化的次一级影响因素。 2)2005~2006年纳木错降水中δ18O的加权平均值约为-18.4‰,6月至10月夏季风期间,降水中δ18O的月均值与月降水量之间存在明显的负相关关系。河水样品的δ18O值变化于-20.0‰到-10.0‰之间,河水中δ18O的季节变化主要受冰雪融水和大气降水中δ18O值的季节变化影响。扎当冰川垭口处雪坑中δ18O纪录能较准确地反映同时期降水中δ18O变化。纳木错湖水中δ18O平均值约为-6.8‰,且有一定的季节变化。 3)纳木错是一个稳定型湖泊,湖水同位素目前处于平衡状态。假定湖区的气候、水文条件保持不变且湖水中最初的δ18O值与入湖水中δ18O值相同,经过湖水同位素平衡过程模拟,表明现代湖水中18O的平衡状态,是在湖面平均相对湿度为56.7%时,经过约106个换水期(约4,727.6年)演变才达到的。
英文摘要: Natural environment has been affected by global warming. It is of great importance to study the global climatic change. Nam Co Basin locates in the central part of Tibetan Plateau, and many glaciers and lake sediments have developed in this basin, so it is an ideal site for studying the palaeoclimate and palaeoenvironment in Tibetan Plateau. Investigating stable isotopic composition of water in the Nam Co Basin can help to reveal the climatologic significance in ice cores and lake sediments. Based on several kinds of water samples in the Nam Co Basin, this thesis analyzes the temporal and spatial characteristics of δ18O in these samples, reveals the variations of δ18O in summer and autumn precipitation and their relations with moisture source and air temperature in Nam Co Basin, and models the evolutive process of oxygen isotope in lake water of Nam Co on the basis of modern mass balance of Nam Co. The following are some results of our study: ● The range of variations of δ18O in summer and autumn precipitation is biggish, and differences of moisture source are the primary factor which influences variations of δ18O in precipitation. According to the air mass backward trajectories, precipitation events are divided into two types: continental and marine precipitation. Positive correlations exist between δ18O and air temperature for both types of precipitation events, suggesting secondary affects of temperature on precipitation δ18O. ● The weighted δ18O of precipitation from 2005 to 2006 in Nam Co Basin is -18.4‰, during the monsoon season, there is an obvious negative correlation between monthly δ18O in precipitation and monthly air temperature. The δ18O values in river water samples vary between -20.0‰ and -10.0‰, the seasonable variations of δ18O in river water are mostly affected by the seasonable variations of δ18O in precipitation and melted snow and glacier water. The records of δ18O in snowpits locate on Zha Dang glacier can reflect the variations of δ18O in contemporaneous precipitation. The average value of δ18O in lake water of Nam Co is -6.8‰, and δ18O values of lake water vary with the changes of seasons during one whole year. ● Nam Co is a steady-state lake, and the oxygen isotope of lake water is in a stable state. Given a long-term stable climatic condition in Nam Co Basin, then the evolution of 18O in lake water is modeled, we find it will take almost 4,727.6 years for lake water to reach isotopic equilibrium.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.itpcas.ac.cn/handle/131C11/1194
Appears in Collections:图书馆_学位论文

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Recommended Citation:
徐彦伟.青藏高原纳木错流域水中氧稳定同位素特征研究[硕士].北京.中国科学院研究生院.2007
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