Water isotope variations in the snow pack and summer precipitation at July 1 Glacier, Qilian Mountains in northwest China  

作　　者：ZHOU ShiQiao NAKAWO Masayoshi SAKAI Akiko MATSUDA Yoshihiro DUAN KeQin PU JianChen 

机构地区：[1]Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China [2]Institute of Plateau Meteorology, China Meteorological Administration, Chengdu 610071, China [3]Research Institute for Humanity and Nature, Kyoto 606-8502, Japan [4]Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan [5]Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China

出　　处：《Chinese Science Bulletin》2007年第21期2963-2972,共10页

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos. 40671045, 40611120140 and 40401054);the Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KZCX2-YW-317);the National Basic Research Program of China (Grant No. 2005CB422004)

摘　　要：This paper presents the stable isotope data of the snow pack and summer precipitation collected at the July 1 Glacier, Qilian Mountains in northwest China and analyses their relationships with meteorologi- cal factors. On an event scale, there is no temperature effect on the δ 18O values in the summer pre- cipitation, whereas the amount effect is shown to be clear. By tracing the moisture transport history and comparing the precipitation with its isotopic composition, it is shown that this amount effect not only reflects the change in moisture trajectory, which is related to the monsoon activities, but is also associated with the cooling degree of vapor in the cloud, the evaporation of falling raindrops and the isotopic exchange between the falling drops and the atmospheric vapor. As very little precipitation occurs in winter, the snow pack profile mainly represents the precipitation in the other three seasons. There are low precipitation δ 18O ratios in summer and high ratios in spring and autumn. The Meteoric Water Line (MLW) for the summer precipitation is δ D = 7.6 δ 18O + 13.3, which is similar to that at Delingha, located in the south rim of the Qilian Mountains. The MWL for the snow pack is δ D = 10.4 δ 18O + 41.4, showing a large slope and intercept. The deuterium excess (d) of the snow pack is positively correlated with δ 18O, indicating that both d and δ 18O decrease from spring to summer and increase from early autumn to early spring. This then results in the high slope and intercept of the MWL. Sea- sonal fluctuations of d in the snow pack indicate the change of moisture source and trajectory. During spring and autumn, the moisture originates from continental recycling or rapid evaporation over rela- tively warm water bodies like Black, Caspian and Aral Seas when the dry westerly air masses pass over them, hence very high d values in precipitation are formed. During summer, the monsoon is responsi- ble for the low d values. This indicates that the monsoon can reach the western part of the QiliThis paper presents the stable isotope data of the snow pack and summer precipitation collected at the July 1 Glacier, Qilian Mountains in northwest China and analyses their relationships with meteorological factors. On an event scale, there is no temperature effect on the 8180 values in the summer precipitsUon, whereas the amount effect is shown to be clear. By tracing the moisture transport history and comparing the precipitation with its isotopic composition, it is shown that this amount effect not only reflects the change in moisture trajectory, which is related to the monsoon activities, but is also associated with the cooling degree of vapor in the cloud, the evaporation of falling raindrops and the isotopic exchange between the falling drops and the atmospheric vapor. As very little precipitation occurs in winter, the snow pack profile mainly represents the precipitation in the other three seasons. There are low precipitation δ^18O ratios in summer and high ratios in spring and autumn. The Meteoric Water Line （MLW） for the summer precipitation is δD = 7.6 8180 ＋ 13.3, which is similar to that at Delingha, located in the south rim of the Qilian Mountains. The MWL for the snow pack is δD = 10.4 δ18O 41.4, showing a large slope and intercept. The deuterium excess （d） of the snow pack is positively correlated with 8180, indicating that both d and 8180 decrease from spring to summer and increase from early autumn to early spring. This then results in the high slope and intercept of the MWL. Sea- sonal fluctuations of d in the snow pack indicate the change of moisture source and trajectory. During spring and autumn, the moisture originates from continental recycling or rapid evaporation over relatively warm water bodies like Black, Caspian and Aral Seas when the dry westerly air masses pass over them, hence very high d values in precipitation are formed. During summer, the monsoon is responsible for the low d values. This indicates that the monsoon can reach the western part of the Qilian Mountains

关 键 词：青藏高原 祁连山 冰川 降水 粒雪 

分 类 号：P4[天文地球—大气科学及气象学]