天目山地区树轮δ^(13)C记录的300多年的秋季气候变化

The Cli mate Change in Autumn Recorded in theδ^(13)C ofTree Rings in the Past300Years at Tianmu Mountain

对采自浙江西天目山地区的柳杉树轮,交叉定年后,测定其δ13C年序列。用趋势比率法去除大气δ13Ca对树轮δ13C年序列的影响后,分析了树轮δ13C年序列对气候要素变化的响应。分析发现:柳杉树轮δ13C年序列的高频振荡与该区9~12月气温及9月降水有较好相关性。重点重建了该地区9月降水量与平均最高气温两个气候要素300多年的气候变化,其变化模式表现为:冷-湿和暖-干的组合特征。统计结果显示:重建序列所反映的旱涝频率分布及其冷暖变化与该区的实测记录结果基本一致。表明:重建序列较好地反映了该区秋季气候变化历史。重建序列所反映的气候变化与我国近500 a的气候变化及该区部分史料记载有较好的对应,并与青藏高原苟鲁错湖泊沉积及新疆阿勒泰地区树轮δ13C记录的气候变化有部分对应,只是冷暖变化的起止时间有错动,反映了气候变化的区域差异。周期分析发现:重建序列含有准58.82 a、21.28 a、13.70 a、3.23 a、2.63 a、2.33 a、2.07 a的周期,这些周期与行星、地心会聚的“力矩效应”变化周期、太阳辐射变化、太阳活动及“准两年振荡”周期相吻合,表明太阳辐射变化及ENSO现象对该区气候变化影响显著,也反映出天目山地区树轮δ13C年序列对太阳活动及大范围的ENSO事件的记录能力。

Based on cross-dated tree ring age, the annual time series of δ^13C in the Cryptomeria Fortunei Hooibrenk ex Otto et Dietr （CF） tree rings collecting from west Tianmu Mountain, Zhejiang Province, were measured. The response of the δ^13C series of CF tree rings to the change of climatic factors was analyzed after obviating the influence of the δ^13Ca variation in atmospheric CO2 on the δ^13C time series of the tree rings by using the Falker＇ s method. It is found that there is a high correlation between the high frequency oscillation of the time series of δ^13C in the CF tree rings and the climatic factors including the temperature in September, October, November and December and the precipitation in September. On the bases, this paper mainly reconstructed the historical changes of the average precipitation and the highest air temperature in September in the past 300 years at Tianmu Mountain area. The climate variability is characterized by the combination of cold-wet and warm-dry. The statistic result shows that the frequency of drought-waterlog and the cold-warm variation reflected from the reconstructed series basically agrees with that recorded by weather station. This indicates that the reconstructed result better reflects the historical changes of climate in autumn at Tianmu Mountain area. The climatic variation reflected from the reconstruction also better corresponds to the climate change in the past 500 years in China and some history records and as well as the lake sediments of Goulucuo, Qinghai-Xizang Plateau, and the tree ring δ^13C records in Altay County of Xinjiang Region but the exchange time from cold to warm has some moving which reflects the regional difference of the climate changes. The spectrum analysis shows that in the reconstructed series there is quasi periodicity of 58.82 a, which is coincident with the ＂moment effect＂ variation periodicity of the planets and earth coming together as well as there are quasi periodicity of 21.28years, 13.70years, 3.23years, 2.63years, 2.33years and 2.07years, which coincide with the solar radiation variation and solar activity and ＂ quasi two-year tropic barometric oscillation＂ （QBO）. This reflects not only the influence of the change of the solar radiation and ENSO phenomenon on the climatic changes, but also the record ability of the time series of δ^13C in tree rings on the solar radiation change and large-scale ENSO events at Tianmu Mountain area.