水体稳定同位素在青藏高原大气环流研究中的应用

Water Stable Isotopes and Their Applications to the Study of Atmospheric Circulations on the Tibetan Plateau

水体稳定同位素作为贯穿水循环的介质,是研究大气环流过程和传输路径的有效手段。介绍了水体稳定同位素技术在青藏高原大气环流研究中的应用,聚焦典型站点降水、河水和冰芯等水体稳定同位素的季节和空间变化特征,揭示了大气环流对地表水稳定同位素高程效应的显著影响,以及大气降水对地表水的主导;引入降水稳定同位素标准判断亚洲夏季风爆发时间;通过冰芯稳定同位素揭示了厄尔尼诺—南方涛动对整个青藏高原水循环的影响及其响应机制的区域差异。在未来的研究中,将加强跟地球系统模型的结合,关注水体稳定同位素在不同时间尺度的控制因子、突变过程以及激发机制,进而量化古气候替代指标中的稳定同位素变化、从较长的时间尺度上重建影响青藏高原的水汽来源的演变历史。同时关注过量氘等具有水汽来源诊断能力的参数,研究其与大尺度环流参数的相关性,从海表温度、蒸发等陆—气相互作用分析并将高原环流过程与全球环流过程紧密结合综合分析。

Water stable isotopes(δ) are inherent in the water cycle,changing during water phase changes,and hence widely used to study moisture trajectory and water cycle. Their application to the study of atmospheric circulations over the Tibetan Plateau(TP)has led to a comprehensive understanding in the past decades. This review focuses on field sampling across the extensive TP,and summarizes the spatial and temporal variation patterns in water stable isotopes in precipitation,surface water and ice cores. Complex circulation patterns are found to affect the altitude effect in water stable isotopes,so that monsoon yields a smaller altitudinal lapse rate than westerly,which in extreme cases can result in increasing isotopic composition with increasing altitudes;though the precipitation isotopes have a prevailing dominance over surface water isotopic features. The sensitive response of precipitation stable isotopes to convection is also applied to the judgement of monsoon onset based on abrupt,continuous and significant decrease in δ. Accordingly,the submonsoon system is found to onset earlier over the Bay of Bengal than the South China Sea and varies diversely under global warming. A long-term perspective into atmospheric circulation over the Tibetan Plateau from ice core δ reveals significant impacts of El Ni?o-Southern Oscillation(ENSO)on the TP,with a dampening effect on the temperature significance of ice core isotopes in the southern TP under the monsoon dominance,while a lagged correlation between ENSO and ice core isotopes in the northwestern TP;all pointing to possible teleconnections between TP climates and sea surface temperature. In future studies,the Earth system models will be relied upon to help reveal physical mechanisms behind complex water stable isotope variations,and comprehend unique isotope variation patterns under extreme climates. Based on modern precipitation δ variation features and abrupt changes and triggering mechanisms,variation history of moisture sources is to be reconstructed from paleoproxies. Besides,isotopic parameters including deuterium excesses have high meteorological synoptic capacity,and would be applied to the analysis of changes in sea surface temperature or evaporation,and hence to facilitate the understanding of sea-air interactions,and the interactions of circulation patterns and water cycles on the Tibetan Plateau with global climate changes.