Variation Analysis Of The Ice Surface Elevation And Volume Of The Glacier No.1 At The Headwater Of Urumqi River During The Recent Three Decades

Glacier No.1 at the headwater of Urumqi River(abbreviation: Glacier No.1) has important significance in the study of glaciers in china, which has the longest continuous monitoring history and most perfect observation data. Numerous observation items has been carried out on the Glacier No.1, such as the changes of glacier terminus, area, and volume, glacier surface movement and so on, and its response process to climate change was analyzed. The reliability and accuracy of research on glacier surface elevation based on mass balance data was restricted to the number of surveying rod and accuracy of measurement, therefore the calculation of the glacier volume by mass balance data existed deficiencies. Due to steep terrain on the surface of mountain glacier, the measurement of Ice-thickness by Radar was difficult to cover the whole glacier, and there were many uncertain factors in the calculation of the glacier volume using spatial interpolation method. The variation of the surface elevation on the Glacier No. 1 was analyzed in this study, based on the surface elevation data from 1980 to 2006. The ice-thickness and volume of Glacier No.1 was calculated by the topographic map of the Glacier No.1 and Glacier No.2, which was drawn in 1986, and the variation of elevation and volume were detailed analyzed. We got the following main conclusions:1) The ice-thickness of the ablation zone on the Glacier No.1 thinned 18.53 m with the annual reduction of 0.74 m. The maximum in the variation of ice elevation appeared in the A row on the terminus and H row on the accumulation zone in the East Branch of Glacier No.1, whose elevation was 3724 m and 4053 m separately. And the maximum in the variation of ice elevation appeared in the E row and I row on the accumulation zone in the West Branch of Glacier No.1, whose elevation was 3972 m and4076 m separately.The change of ice-surface elevation in West Branch was greater than in East Branch of the Glacier No.1, affected by temperature significantly. The change of ice-surface elevation was an complex process. In addition to the temperature, glacier movement also has an impact on it. Ice in the accumulation zone was transported to the ablation zone; the ice surface elevation showed sinking in the accumulation zone flow and showed upward flow in the ablation zone.2) Variation of glacier volume mainly manifested as the change of glacier surfaceelevation and area. The area of the Glacier No.1 reduced by 0.31 km2, and the average annual ablation was 0.006 km2 with the rate of annual reduction was 0.32% from 1986 to 2006. Analysis showed that the ablation of glacier mainly occurred in the ablation zone, the glacier terminus retreat was not obvious contribution to the glacier change, the loss of the glacier area mainly occurred below 4035 m.Through topographic map of Glacier No.1 and Glacier No.2 drawn in 1986, the maximum thickness in East Branch(3900 m) and the West Branch(4055 m) was132.564 m and 129 m separately. The average thickness of the glacier ablation zone was68 m, the glacier volume was 0.0758km3.The volume reduced by 0.0210 km3, the ratio of volume loss was 25.8% with the annual loss of 1% from 1981 to 2006.Compared with glacier area change,variation of glacier volume was more sensitive to the climate change.The rise of the temperature was the the dominant factor of glacier retreat, glacier retreat leaded to the equilibrium line rose, the ratio of accumulation area decreased, the ice albedo decreased, causing glaciers absorb more energy, thereby accelerated the glacier ablation.