DENSIFICATION PROCESS WITHIN THE NEAR-SURFACE LAYER OF THE ANTARCTIC ICE SHEET

The densification process within the near-surface layer of Antarctic Ice Sheet is dominated by the environment and exhibits geographic zonality, In this article, the processes are found to be of three types: warm, cold and alternate, on the basis of the studies on a lot of shallow snow/firm cores from Wilkes Land, Antarctica, and the available data. Warm type densification takes place mainly on the periphery of the Antarctic Ice Sheet, where the mean annual temperature is about --10----15℃. High temperature in summer and consequent melting and infiltration are the main factors influencing the densification process. Cold type densification occurs in the huge central region of the Antarctica, where the mean annual temperature is below --25℃, with the maximum below 0℃ in summer. In this region, ice sintering is a main cause for the densification. The alternate type densification occurs in the transition zone between the above two regions, where the mean annual temperature is --15----25℃ and the highest

DENSIFICATION PROCESS WITHIN THE NEAR-SURFACE LAYER OF THE ANTARCTIC ICE SHEET

The densification process within the near-surface layer of Antarctic Ice Sheet is dominated by the environment and exhibits geographic zonality, In this article, the processes are found to be of three types: warm, cold and alternate, on the basis of the studies on a lot of shallow snow/firn cores from Wilkes Land, Antarctica, and the available data. Warm type densification takes place mainly on the periphery of the Antarctic Ice Sheet, where the mean annual temperature is about -10--15℃. High temperature in summer and consequent melting and in filtration are the main factors influencing the densification process. Cold type densification occurs in the huge central region of the Antarctica, where the mean annual temperature is below -25℃,with the maximum below 0C in summer. In this region, ice sintering is a main cause for the densification. The alternate type densification occurs in the transition zone between the above two regions, where the mean annual temperature is-15--25℃ and the highest temperature is 0℃ in certain summers, Both the melting and sintering are the main cause for alternate type densification. These three types of densification process are greatly different both in macroscopic and microscopic charac teristics, such as the density-depth relation, compactive viscosity coefficient, crystal size and crystal growth rate, c-axis orientation and elongation of snow/firn crystals in the near-surface layer.