南极威尔克斯地SGR钻孔处雪冰转化过程中的密度变化特征

本文着重描述了SGR钻孔处冰盖上的积雪在密实化过程中的特征变化,并对该过程进行了分段的和全面的回归分析.结果表明,冰盖密度随深度增大,但增长幅度随深度减小.作者提出密度变化减小度的概念.计算得出的所研究冰芯钻取点的密度变化减小度为-0.15kg/m~3·m~2,粒雪成冰前的密实速率平均值为4.08kg/m~3·a.本文得到的冰盖密度变化“临界点”与以往报道的有所不同.分析这一现象时,作者强调当积雪还在活动层时冰盖温度的影响,并以此解释密度剖面的异常变化以及离差的回升.特别指出,积雪的密度变化具有气候学意义,它在一定程度上能够反映出积雪形成及变化过程中气候变化的某些信息.本文由密度变化确定的钻孔点雪冰转化深度为50米.

CHARACTERISTICS OF DENSITY VARIATION IN THE PROCESS OF TRANSITION OF SNOW TO ICE IN THE ZONE OF BOREHOLE SGR ON WILKES LAND, ANTARCTICA

A snow/ics core of more than 60 m long borehole drilled at the Law Dome Ice Cap, Wilkes Land, Antarctica, has been studied. The characteristic variation in the densification of snow in the zone of borehole SGR is described in present work. More over, a regression analysis was made on this process. The results suggest that snow/firn density of the ice sheet increases, but the extent of increment is reduced with increasing depth . A cocept called "retardation of density variation "is proposed . The retardation of density variation for the site where the core was used in this study is -0. 156 kg/m3 · m2. The mean snow/firn densification rate before it becomes ice is 4. 08 kg/m3 · a . The critical points of density variation for the ice sheet is some different from those reported in previous works . In the analysis of this feature , the authors emphasize the effect of the temperature of ice sheet on the snow as it was still in the active layer. And the anomalous density variation and the picking up of its deviation are attribued to this mechanism too . It has been especially pointed out that in the polar region the densification feature ofsnow is significant in climatology. To some extent it provides an information on the climate variation when the snow cover was formed. The transition depth of snow to ice determined from the density variationis 50 m for the drill site , it is near the ice formation depth of snow discovered and reported by otyers from other territories of Antarctica .