One of sea ice core samples was taken from Arctic by the First Chinese National Arctic Research Expedition Team in 1999. 20 vertical and 2 horizontal ice sections were cut out of the ice core sample 2.22 m in length, which covered the ice sheet from surface to bottom except losses for during sampling and section cutting. From the observation and analysis of the fabrics and crystals along the depth of the ice core sample, followings were found. Whole ice sheet consists of columnar, refrozen clastic pieces, granular, columnar, refrozen clastic pieces, granular, columnar and refrozen clastic pieces. This indicates that the ice core sample was 3-year old, and the ice sheet surface thawed and the melt water flowed into ice sheet during summer. Hence, the annual energy balance in Arctic can be determined by the ice sheet surface thawing in summer, and bottom growth in winter. The thickness of the ice sheet is kept constantly at a certain position based on the corresponding climate and ocean conditions; A new kind of hydrodynamic-effected ice crystal was found in the analysis and was defined as refrozen clastic pieces. The newly refrozen clastic pieces are explained as that they belong to the ocean dynamic broken ice pieces that come into contact with ice sheet due to buoyancy and move with the whole ice sheet. While these pieces moved to a colder zone, they were refrozen. Therefore, its structure is different from that of first-year ice and also can explain why there are typical Arctic sea ice micro-algae in the ice core sample. The age of the ice sheet is determined to be from 1997 winter to 1999 summer.
