南极洲乔治王岛柯林斯冰帽小冰穹顶冰芯数学模式初步断代

冰芯钻取后，样品截取原则和环境记录的初步解释要求对年代－深度剖面有一初步了解，即要求建立冰体随深度变化的时间尺度。根据柯林斯冰帽一年多野外实测资料所揭示的小冰穹运动状况、温度分布、物质平衡和动力学特征，本文采用Ｄａｎｓｇａｒｒｄ－Ｊｏｈｎｓｅｎ模型和等温冰体流动模型（ｎ＝３），分别对一支８０．２ｍ冰芯的时间尺度进行初步估算。结果表明两种模型断代结果非常接近，在距冰床１０ｍ深度处，两模型分别给出１８９７年和１８５４年的冰龄。对比指出两种模型计算出的冰帽各深度冰龄最大误差不大于２％。与冰芯中上部含深褐色火山灰冰层的历史记录年代相比误差小于３％。

A PRELIMINARY AGE DETERMINATION WITH NUMERICAL MODELLING FOR AN ICE CORE EXTRACTED FROM LOW DOME OF COLLINS ICE CAP,KING GEORGE ISLAND,ANTARCTICA

After coring,ice sampling strategies and preliminary interpretations require a preliminary understanding of age depth profiles of the core,which means the well established time scales are necessariated. According to ice flow state,temperature distribution,mass balance and dynamic characteristics of Low Dome on Collins Ice Cap,revealed by observational data collected in situ for more than one year,Dansgaard Johnsen model and isothermal ice flow models for n=3 are adopted respectively to calculate the time scales of a 80. 2m ice core.Our calculation show a very approximate time scale of the core,at depth of 10m above the bedrock,ice dating of 1879 a and 1854 a B.P.are obtained by these two models respectively.The maximum error between two model calculation is no more than 2% at each depth of the ice cap.Comparisons with the chronical records of the volcanic ash layers contained in the middle upper part of the core suggest an age error less than 3%.