东南极洛多姆冰帽粒雪晶粒的生长

GRAIN GROWTH IN FIRN ON LOW DOME ICE CAP, xEAST ANTARCTICA

对东南极洛多姆冰帽16个地点粒雪晶粒平均面积的详细研究表明,表层数米内晶粒的迅速生长在低积累区较为显著,随积累率增大逐渐减弱,原因可能是随积累率增大粒雪在近表层停留时间变短。晶粒平均面积随深度及年代的变化都可以较好地用线性关系近似表示。由于采样地点间积累率的巨大差别,积累率对晶粒平均面积深度关系影响较大。随积累率增加,晶粒平均面积的增加速率随深度明显减小。晶粒生长速率随温度的关系在-17℃左右开始和Gow(1975)的关系偏离,反映出晶粒生长过程的自扩散激活能可能和温度有关,其值随温度升高而增大。

The detailed studies of firn grain mean area at 16 sites on Law Dome, East Antarctica, indicate that the enhanced grain growth in the several metres neai the snow surface is more apparent in low accumulation areas, declining with the increase of accumulation rate. This can be contributed to the short staying period of the snow near the surface caused by the higher accumulation rate. The variation of mean grain area with both depth and age can be approximately represented by linear relations. The rate of increase of mean area versus depth decreases markedly with accumulation rates due to the very large differences in accumulation rates between the sampling sites. Growth rate versus temperature at about-17癈 starts to depart from the temperature dependence of crystal growth rate established by Gow (1975) suggesting that the activation energy for the growth process increases with increasing temperature.