近800年来内蒙古岱海地区古气温的定量重建

An 800-Year Temperature Reconstruction in Daihai Lake Area of Inner Mongolia

根据对现代湖水、现生介形类壳体以及湖泊沉积岩芯中同一种属介形类壳体的Sr Ca分析 ,利用现代湖水Sr Ca与湖水盐度的关系 ,确定了不同沉积时期湖水盐度 ;其次 ,在室内模拟实验 ,建立了湖水盐度与湖水氧同位素的函数关系 ;结合2 1 0 Pb测定沉积速率和1 4C测年资料 ,利用沉积剖面的自生碳酸盐氧同位素及由湖水盐度推算的湖水氧同位素组成 ,定量恢复了不同时期的湖水温度 ,进而根据碳酸盐结晶时水温与年均气温关系推测了古气温。结果表明 :在近 80 0年内蒙古岱海地区的气温变化序列中 ,中世纪暖期、现代小冰期以及近百年增温均有明显表现。研究时段内 ,岱海地区中世纪暖期比当代 30年的年均气温高 1℃以上 ;在公元 12 4 0年左右突然降温过程表现特别突出 ,在其后约 6 0年的时段内气温下降 1.8℃ ;小冰期最大降温幅度 2℃以上 ,大于华北其它地区。不同于我国西部古里雅冰芯的记录 ,岱海地区近百年增温程度仍没有达到中世纪暖期水平 ,预示气候变暖对我国西部地区的影响将大于东部。

Combined the analysis of the oxygen isotopic composition of the authigentic carbonates in sediment core of Daihai Lake, establishment of the function between water salinity and oxygen isotopic composition, with the reconstruction of lake water salinity, the temperature of lake water during the carbonate crystallization was reconstructed. Then the yearly average air temperature was deduced according to the difference between the lake water temperature of the carbonate crystallization and the yearly average air temperature. The deduced curve of yearly average air temperature during the past 800 years showed three obvious stages, namely the Medieval Warm Period, the Little Ice Age, and the warming stage of the last hundred years. The temperature of the Medieval Warm Period in the research period was 1℃ higher than that of average temperature of recent 30 years. From 1240 A. D. to 1300 A. D., the temperature decrease 1.8℃, showing abrupt changes of climate. The temperature in the coldest period of the LIA was 2.2℃ lower than that of present. Since 1880 A.D., the temperature have kept warming continuously, and the increasing amplitude reaches more than 1℃. Different from the climate feature recorded by Guliya ice core, in the west part of China, the last hundred years' warming in Daihai Lake area has not reached the warm degree of the Medieval Warm Period, probably suggesting that the influence of global warming on the west China is more heavier than the east China.