利用红柳沙包氢氧同位素重建罗布泊地区近160年间气候要素

RECONSTRUCTION OF THE CLIMATE PARAMETERS IN LOP NUR REGION OVER THE PAST 160 YEARS BASED ON THEδD AND δ^(18)O IN TAMARIX CONE SEDIMENTARY VEINS

新疆罗布泊地区存在的红柳沙包不仅是高分辨率的计年载体,同时蕴含丰富的环境演化信息。本文通过对罗布泊地区典型红柳沙包沉积纹层样品的氧氢同位素测定和分析,建立了红柳沙包沉积纹层的δD和δ^(18)O序列,并依此重建了罗布泊地区过去163年间的平均气温、相对湿度、降水量等气候要素变化序列。重建结果表明,3月份平均气温为7.39℃,其中1844～1960年略有上升,1960～1980年快速下降,到1980～2006年又开始回升;2～4月份平均空气相对湿度为31.72%,变化幅度比较大,其中1844～1915年相对较高,1916～1960年相对较低,1960～1990年左右是相对湿度高峰期,1990年左右至今接近平均值;7月份平均降水量为2.55mm,总体变化幅度不大,其中从20世纪30年代到60年代降水量很少,20世纪60年代以后有逐渐增加的趋势。

Tamarix cone exists widely in the Lop Nur region of Xinjiang. It not only serves for high-resolution dating,but also contains a wealth of information on environmental evolution. The studied typical Tamarix cone in Lop Nur region is located at 39.58°N,89.78°E, and contains 168 layers with clear sedimentary veins that indicates a time period of 168 years which was verified by of the 21°Pbex dating methods. The contents of D and 18O of Tamarix leaves and twigs in Tamarix cone sedimentary veins were measured by a mass spectrometer of MAT-253 in Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences. Based on the analyzed data of 8D and δ18O, the time sequences of 8D and δ18O are established. Results show that there are an obvious positive correlation between 8D and minimum air temperature, an obvious negative correlation between 6D and relative humidity in Tamarix growth season; the correlation between δ18O and relative humidity are negative while the correlation between δ18O and mean average air temperature are positive, vice versa（ except in May） ; the correlation between 6D or °and precipitation are all negative. The reconstructed climate factors show that in the period from 1844 to 1960 the mean air temperature has increased slightly. It decreased quickly from 1960 and increased again since 1980. In the past 163 years,the mean air temperature in March is 7.39℃ ,among which it is 7, 4 in 1844 - 1927, and 7.7℃ in 1928- 1963. In 1964- 2006 it is 7. 4℃ and is lower than that in the last 2 periods, Therefore, the years of 1928 - 1963 is obviously an warm period which lasted for 36 years. The mean relative humidity in period of February to April is 31.72% with larger fluctuations. It is higher in 1844 - 1915 ,lower in 1916 ~ 1960, reaching to a peak value in 1960 -1990, and being close to the mean value in about 1990. The precipitation in July is 2.55mm; much less before 1960＇s and gradual increases afterwards. In the Lop Nur region, the mean air temperature in March could be used for division of cool and warm periods, while precipitation in July could be used for division of drought and humid periods.