新疆阿勒泰地区小冰期特征的树轮δ^(13)C记录

Tree-ring δ^(13)C Records in the Little Ice Age in Altay Prefecture of Xinjiang Region

建立了新疆阿勒泰地区一个长约 45 0a的落叶松树轮碳同位素年表 .该年表一个最为明显的特点是 185 0年后年轮δ13 C显著降低 ,这是化石燃料燃烧和土地利用方式改变的缘故 .在 15 5 0— 185 0年期间 ,该年表经历了明显的距平“正负” (即暖冷 )变化 :17世纪年轮δ13 C值相对偏负 ,气温较低 ,18世纪年轮δ13 C值相对偏正 ,温度较高 .根据已有的树轮δ13 C温度系数 ,17世纪的温度相对偏低约0 6 7～ 2 46℃ .广泛的区域性对比表明 。

Increasing concern on future climate changes and their potential impacts on mankind prompts scientists to explore a variety of historical and natural archives that can infer the past climate changes. Of the various land-based short-term palaeoclimatic indicators, tree rings offer a great promise because of their high resolution (1 year or less). In this context, ring width, ring density and stable isotope ratios of tree ring have been studied for possible climatic correlations. The δ 13C values in annual growth rings of trees should represent a high resolution record of δ 13C values of atmospheric CO 2, or physiological response of plant relating to climatic and environmental changes or a combination of both. There is currently an expectation thatδ 13C values in tree rings could be less sensitive to random effects than radial growth. So a ca 450-year chronology of tree-ring stable carbon isotope was developed from Larix sibirica in the Altay County of Xinjiang Region. A rapidly decreasing trend, the most dramatic isotopic event in the chronology, has appeared since 1850, which was attributed to combustion of fossil fuel and change in land use. From 1550 to 1850, there were obvious changes of tree-ring δ 13C or temperature in the chronology: Tree-ring δ 13C or temperature was lower in the whole 17 thCentury while was higher during the 18 th Century. Using the available temperature coefficient of tree-ring δ 13C, a decrease of 0^67～2^46 ℃ in the 17 th Century is found. All kinds of evidence from different regions showed that the temperature changes of the Little Ice Age disclosed by the tree-ring δ 13C chronology were reliable.