Physical properties of firn cores from the 1995/96 and 1996/97 field seasons

The paper focuses on studies of snow-pit samples and shallow firn cores taken during the 1995-96 and 1996-97 field seasons at Amundsenisen, Dronning Maud Land, Antarctica. The dating of the firn is based on the artificial tritium distribution in the snow cover and on several reference horizons identified by electrical measurements. The early 1964 through 1965 horizon is marked by the deposition of sulfate released to the atmosphere during the eruption of the Agung volcano in March 1963; this horizon was detected by dielectric profiling and electrical conductivity measurements; the proof by chemical analysis has still to be seen. At the ten investigated sites on Amundsenisen the 1964-65 horizon was identified 4.1-5.7 m below the surface. The accumulation rates on Amundsenisen are 41-91 kg/m**2/a. The cores are up to 100 years old. A relationship between isotope content and the mean air temperature on a regional scale can be based on measurements of firn temperature at 10 m depth at the drilling sites. Between Neumayer station at the coast and Heimefrontfjella, the temperature gradient of the deuterium content is 9.6 per mil/K. South of Heimefrontfjella, on the Amundsenisen plateau, it is only 5.5 per mil/K. Time series of yearly accumulation rates show no significant trend. For the isotope records a significant trend to higher values with gradients of 0.1-0.2 d2H per mil/a can be seen in five of the ten time series.

本研究聚焦1995-1996及1996-1997年度南极毛德皇后地（Dronning Maud Land）阿蒙森冰原（Amundsenisen）野外作业期间采集的雪坑样品与浅层粒雪芯（firn core）。粒雪定年以积雪层中的人工氚（tritium）分布为依据，并结合电学测量识别出的多个参考层位开展。1964至1965年的参考层位由1963年3月阿贡火山（Agung volcano）喷发至大气中的硫酸盐沉降所形成；该层位通过介电剖面法（dielectric profiling）与电导率测量（electrical conductivity measurements）得以检出，但其化学分析验证工作仍有待完成。在阿蒙森冰原的10个研究点位中，1964-1965年参考层位位于地表下4.1~5.7米处。阿蒙森冰原的积雪积累率为41~91 kg/m²/a。本次采集的粒雪芯年代最远可达100年。区域尺度上同位素含量与平均气温的关联，可通过钻探点位10米深度处的粒雪温度测量结果建立。在海岸诺伊迈尔站（Neumayer station）与海姆弗伦特丘陵（Heimefrontfjella）之间，氘含量的温度梯度为9.6‰/K；而在海姆弗伦特丘陵以南的阿蒙森冰原高原，该梯度仅为5.5‰/K。年积雪积累率的时间序列未呈现显著变化趋势。在10条同位素时间序列中，有5条呈现出显著的升高趋势，其氘同位素比值（d2H）变化梯度为0.1~0.2‰/a。