地理学报 ›› 2015, Vol. 70 ›› Issue (1): 97-109.doi: 10.11821/dlxb201501008

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天山地区大气降水氧同位素的影响因素及其对西风环流变化的指示意义

刘小康(), 饶志国(), 张肖剑, 黄伟, 陈建徽, 陈发虎   

  1. 兰州大学西部环境教育部重点实验室,兰州 730000
  • 收稿日期:2014-09-12 修回日期:2014-11-11 出版日期:2015-01-20 发布日期:2015-06-17
  • 作者简介:

    作者简介:刘小康(1990-), 男, 甘肃天水人, 博士研究生, 主要从事地球化学与过去气候变化研究。E-mail: liuxk07@lzu.edu.cn

  • 基金资助:
    国家自然科学基金项目(41372181,41171091,41130102);兰州大学中央高校基本科研业务费专项资金(lzujbky-2014-260)

Variations in the oxygen isotopic composition of precipitation in the Tianshan Mountains region and their significance for the Westerly circulation

Xiaokang LIU(), Zhiguo RAO(), Xiaojian ZHANG, Wei HUANG, Jianhui CHEN, Fahu CHEN   

  1. Key Laboratory of Western China's Environmental Systems (Ministry of Education), Lanzhou University, Lanzhou 730000, China
  • Received:2014-09-12 Revised:2014-11-11 Online:2015-01-20 Published:2015-06-17
  • Supported by:
    National Natural Science Foundation of China, No.41372181, No.41171091, No.41130102;Fundamental Research Funds for the Central Universities, No.lzujbky-2014-260

摘要:

利用全球降水同位素观测网(GNIP)提供的乌鲁木齐大气降水氧同位素(δ18Op)观测数据(1986-2003年),结合和田δ18Op数据及天山冰芯δ18O记录,分析了天山地区δ18Op在年内和年际尺度上的变化特征,及其与主要气候要素(温度和降水量)的关系。结果表明,年内尺度上,δ18Op与月均温和月降水量均为显著正相关,表现出明显的“温度效应”;年际尺度上,加权平均年δ18Op与年均温度却呈现负相关关系,与降水量仍为正相关。近40~50年的天山地区4支冰芯的δ18O具有整体偏负的变化趋势,与研究区逐步升高的温度呈反向变化,说明在年际至年代际尺度上,这一区域δ18Op与温度之间的负相关关系是客观存在的。进一步对研究区水汽来源路径的对比分析发现:δ18Op值偏负的高温年份(1997年)的暖季水汽相对更多来源于远源的高纬度区域,而δ18Op值偏正的低温年份(1988年)则相对更多来自近源的中、低纬度区域;同时,研究区上风方向的欧亚大陆14个GNIP站点1997年和1988年的暖季加权平均δ18Op值存在高纬度区域偏负而中、低纬度区域偏正的特征;这些结果说明年际至年代际尺度上,天山地区δ18Op与温度之间的负相关,本质上指示了西风环流南北摆动所引起的水汽来源变化,可以作为西风环流变化的指示器。

关键词: 天山地区, 乌鲁木齐, δ18Op, 水汽来源, 西风环流

Abstract:

Proxy records of the oxygen isotopic composition of meteorological precipitation (δ18Op) preserved in archives such as ice cores, lacustrine carbonates and stalagmite calcite are important for paleoclimatic studies. Therefore, knowledge of the variations and controlling mechanisms of modern δ18Op on different time scales is necessary. Here, we investigate the linear correlations between δ18Op and corresponding temperature and precipitation on monthly and inter-annual timescales, using data from the Urumqi (1986-2003) and Hotan stations of the Global Network of Isotopes in Precipitation (GNIP), and δ18O data from 4 ice cores in the adjacent Tianshan Mountains. Consistent with previous reported results, modern δ18Op variations on a seasonal time scale in the Tianshan region are mainly controlled by a 'temperature effect' (indicated by a significant positive correlation between δ18Op and temperature), with more positive δ18Op values occurring in summer. However, on an inter-annual timescale, there is a weak inverse correlation between weighted average annual δ18Op and annual average temperature at Urumqi. This finding is supported by the inversely varying trends of δ18O data from 4 ice cores in the central and eastern Tianshan Mountains compared to annual average temperatures in the same region during the past 40-50 years. The data from Urumqi station and the 4 ice cores demonstrate that the inverse correlation between δ18Op and temperature on inter-annual to decadal time scales is genuine. Analysis of water vapor sources and pathways for the warm year of 1997 and the cold year of 1988 reveal that more water vapor for the Tianshan area was derived from long-distance transport from high-latitude sources than during the warm year of 1997; and that more water vapor was transported from more proximal sources from mid- to low-latitude areas during the cold year of 1988. In addition, the δ18Op values are more negative in the high latitude areas than those in mid- to low-latitude areas in the Eurasian continent at the upper wind direction of Tianshan Mountains region, according to the weighted averaged warm season (May to September) δ18Op values for 14 GNIP stations in the years 1997 and 1988. Due to the distribution of δ18Op within the Eurasian continent, the relative shift of water vapor sources between warm and cold years convincingly explains the observed variations of δ18Op in the Tianshan area. Therefore, we conclude that variations in δ18Op in the Tianshan Mountains region are mainly controlled by changes in water vapor sources which are ultimately caused by northward and southward shifts in the Westerly circulation.

Key words: Tianshan Mountains, Urumqi station, δ18Op, water vapor sources, Westerly circulation