摘要
古里雅冰芯高分辨率地连续记录了近2000年来的气候环境变化。以δ18O和冰川积累量为指标的气候变化记录的重建表明，温度的波动频率大于降水波动频率，但每次干湿变化中的幅度却又大于温度变化幅度。同时，可以明显看出降水变化滞后温度变化的特征。以Na＋，Mg2＋，Cl－，SO^2-_4等阴、阳离子为指标的大气成分和环境变化记录的重建，揭示了青藏高原地区大气成分和环境变化与气候变化的密切关系。
The Guliya ice core, 309m long, is the longest one among the ice cores from mountain glaciers in middle and low latitudes. Based on the data of δ18O, glacial accumulation rate, major anions and main cations in the Guliya ice core, climatic and environmental changes in the past about 2 000a are studied in this paper.In the northern part of Qnghai-Xizang (Tibet) Plateau, it is found that δ18O and glacial accumulation rate are the reliable indexes of air temperatUre and precipitation respectively. Therefore, the variations of temperature and prtalpitahon can be reconstructed by δ18O and glacial accumulation rate recorded in the Guliya ice core. The time-depth relation in the upper part of the ice core, which is a base for reconstructing the climatic and environmental changes recorded in the ice core in the past about 2000a, is established through the annual dirty layers. By comparison of the secular trends of the variations of temperature and precipitation in the past 2000a revealed from the Guliya ice core, it is showed that there is a positive correlation between them, but thes correlation becomes weak within short time anies. For instance, frequency of the variations of temperature is higher than that of precipitation; the variations of dry and wet, are not always in phase with the variations of cold and warm, and an mouse or a decrease in precipitation occur after climate warming or cooling, the lag time is about 50 ~ 100a, this phenomenon is more obvious in the period of temperature decrease than in the period of temperature rise.In the recent about 2 000a, climate is getting warmer and wetter. Around 1100 A.D. was a key transition period of climatic change, it was cold and dry before the period and warm and wet after the period. In the course of climate warming and transitional, there were many abrupt climatic events, in which, abrupt changes in temperature occurred in the transitional periods of climate from cold to warm and from warm to cold. Abrupt changes inprecipitation were also remarkable, but not related to the abrupt changes in temperature.Maximum entropy spectrum analysis for the variations of temperature and precipitation show that their variations are related to solar activity.Ca2+, Mg2+, Na+,Cl- and SO^2-_4 are the sensitive cation and anion indicators of dust in the Guliya ice core' Among them, the variations of Ca2+ and Mg2+ concentrations mainly reflect the changes in compositions of crustal materials, however, the variations of Cl-, SO^2-_4 and Na+ concentrations were not only controlled by crustal materials but also related to the evolutions of the lakes on the Qnghai-Xizaing (Tibet) Plateau. Thus reconstructions of atmospheric environmental changes, Ca2+, Mg2+, Na+, Cl- and So^2-_4 as the indexes, have an important role in the study of the correlation among the variations of atmospheric compositions and environment and climate in the Plateau. In the Guliya ice core, concentrations of all above cations and anions had decreased gradually in the courses of their fluctuations since the begining of the Christian era, however the magnitudes of the flutuations of Na+, Cl- and SO^2-_4 concentrations were larger than that of Ca2+ and Mg2+ concentrtions. There bolted that the content of crustal dust in the atmosphere decreased to some extent, and the folding effects of the materials from salt lakeS and crust were obvious on influencing the concentrations of the ions. Thus it is concluded that the changes of compositions of crustal materials control the trends of the variations of Ca2+ and Mad+ concentrations, and the materials from the lakes in the Qinghai-Xizang Plateau modified the magnitudes of the fluctuations of Na+, Cl- and SO^2-_4 concentrations.Through studying the correlation among the concentrations of cations, anions and δ18O, it is found that the general trend of the variations of Ca2+ and Mg2+ concentrations decreased gradually, and the general trend of the variations of δ18O increased gradually, Which indicates that the content of crustal dust in the atmosphere became less and less while
出处
《第四纪研究》
CAS
CSCD
北大核心
1997年第1期52-61,共10页
Quaternary Sciences
基金
杰出青年基金
