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The air-bubble formation has been studied experimentally in the Dasuopu ice core from the northern slope of Mount Xixabangma. It was found that air-channel volume decreases gradually, but the firn remains permeable down to the depth above the transition of firn to ice, i. e., about the depth of the air-channels closing off to be isolated bubbles. Apparently, there exists an age difference between air trapped in bubbles and surrounding ice. Only when the air channels close off completely, the age of the air increases in the same rate as the surrounding ice. Air-bubbles formed in different depths at different sites depending on accumulation rate and mean annual temperature, but approximately at a mean density of 0.79～0.83 Mg·m -3 . The air-channels in the Dasuopu firn core closed rapidly in the depth between 40 and 47 m, and 50% of air-bubbles were formed in the depth of 45 m. It is calculated that the age difference between air and its surrounding ice is 59 a, and the bulk age distribution width of air trapped in ice bubbles is 11 a.
The air-bubble formation has been studied experimentally in the Dasuopu ice core from the northern slope of Mount Xixabangma. It was found that air-channel volume decreased gradually, but the firn remains permeable down to the depth above the transition of firn to ice, ie, about the depth of the air-channels closing off to be isolated bubbles. the there is an age difference between air trapped in bubbles and surrounding ice. only when the air channels close off completely, the age of the air increases in the same rate as the surrounding ice. Air-bubbles formed in different depths at different sites depending on accumulation rate and mean annual temperature, but about at a mean density of 0.79-0.83 Mg · m -3. The air-channels in the Dasuopu firn Core closed rapidly in the depth between 40 and 47 m, and 50% of air-bubbles were formed in the depth of 45 m. It is calculated that the age difference between air and its surrounding ice is 59 a, and the bulk age di stribution width of air trapped in ice bubbles is 11 a.