西南极乔治王岛冰芯研究——冰雪层定年、微粒记录及离子迁移  

Research on Ice Core Record fromm King George Island,West Antarctica: Dating, Particles and Ion Elution

作　　者：张小伟[1] 康建成[1] 周尚哲[1] 

机构地区：[1]兰州大学资源环境学院

出　　处：《冰川冻土》2003年第5期533-540,共8页Journal of Glaciology and Geocryology

基　　金：科技部"南极地区地球环境监测与关键过程研究"和"中国南极考察科学研究计划"项目(2001DIA50040 03);"南极冰雪圈特征及气候环境研究\"项目;上海市引进海外高层次留学人员专项资助

摘　　要：在分析南极乔治王岛冰帽大冰穹顶部降水和成冰条件的基础上,利用冰芯上部层物理特征参数确定的5个年层及其附近气象站相应的降水记录,结合多年降水资料将大冰穹45m冰芯划分为15个年层.应用此年层剖面,证实了微粒含量的两个异常峰值分别对应于1987年Deception岛和1980年的SealNunataks两次火山喷发.乔治王岛冰帽属于温性冰帽,大、小冰穹冰芯阴阳离子受沉积后融水渗浸淋溶作用的影响.对冰芯阴阳离子的淋溶次序分析显示,大冰穹为SO2-4>Mg2+>Ca2+>K+>Cl->Na+>NO-3>Br-,而小冰穹为Mg2+>Ca2+>SO2-4>K+>Cl->Br->Na+.As a temperate glacier, melting takes place and causes migration of water and chemical constituents in the snow and ice. The upmost 20 m ice core (about 5 years) of the Big Dome, King George Island, West Antarctica, can be dated by physical and chemical seasonal variations. Based on high accumulation and other climate condition, it is assumed that there is a linear relation with a constant k between the accumulation on the top of ice cap and precipitation at the shore of King George Island. By compared the top annual layers with corresponding precipitation during the 5years, it is found that \%k\%=3\^98. With the value, the 45 m ice core is dated to be totally 15 years. Again it is revealed that the particle profile in the 45 m ice core has not been affected by melting and can be used to reconstruct paleo\|environment. There are two exceptional peaks located at about 20 m and 38 m depths, respectively. Applying the dated result, the two particle peaks are determined to correspond to the Deception Island eruption (1986\_1987) and Seal Nunataks volcano eruption (1980). Major ions concentrations in both ice cores of the Big Dome and Small Dome reduce with depth in general, which indicate that ion elution process occurs during melting. It is found that the average major ion concentrations of five depth segments in both ice cores reduce as exponent functions \%C=C\-0×e\+\{-λh\}\%, where h is the depth, \%C\-0\% is the initial concentration, \%C\% is the concentration at depth \%h\%. According to the coefficient \%λ\%, the preferential ion elution orders are determined as SO\+\{2-\}\-4 >Mg\+\{2+\}>Ca\+\{2+\} >K\++>Cl\+->Na\++>NO\+-\-3>Br\+- on the Big Dome and Mg\+\{2+\}>Ca\+\{2+\}>SO\+\{2-\}\-4>K\++>C\+l->Br\+->Na\++ on the Small Dome. The location difference of major ions within the ice crystal lattice is the main cause of the preferential elution.

关 键 词：西南极 乔治王岛 冰芯 冰雪层定年 微粒记录 离子迁移 

分 类 号：P343.6[天文地球—水文科学]