科其喀尔冰川冰面湖温度变化及其热机制

Thermal regime of a supraglacial lake on debris-covered Koxkar glacier,southwestern Tianshan,China

基于2007年7～9月对科其喀尔冰川消融区冰面湖、表碛、裸冰的温度和消融观测，分析三者的温度变化特征及其差异，探讨冰而湖的热机制。结果表明：科其喀尔冰川冰面湖表层水温受瞬时天气状况影响明显，变化趋势与气温一致，但不如气温变化剧烈并有1～3h滞后性；由于白天冰川融水注入与表层暖水混合下沉，深层湖水在一天的14～16时左右形成低温谷，致使深层水温变化曲线呈“V”字形，具有明显的日变化特征;夏季湖面平缓了湖面上气温的变幅，冰面湖表层温度变化幅度介于表碛0．2～0．5m深处的温度变化幅度之间。对比表碛、冰面湖和裸冰三类下垫面，冰面湖的温度垂直递减率绝对值最小，为0．33℃／m，反映在冰川消融区不同类型下垫面中，冰面湖向下层输送热量的能力较其他下垫面类型强。

Based on the scientific expedition carried out on Koxkar Glacier, Southwestern Tianshan, July to September, 2007, the temperature variations of supraglacial lake, debris, and debris-free ice at different depths were analyzed and the thermal regime of the supraglacial lake was discussed. It is found that the surface water temperature of the supraglacial lake is obviously impacted by the instantaneous weather conditions and fluctuated with air temperature but usually lag behind the changing of air temperature. The variation trends for temperature in deep water performs a distinctly daily V-shape in which the zeroish melt water from the glacier surface inpour the lake and mixed with the relatively high temperature of lake surface water in the daytime, and when the water temperature rises to about 4℃, it sinks down immediately and brings about the relatively low temperature trough in the deep water in the middle of the daytime. In comparison of the thermal state of supraglacial lake with the debris and debris-free ice, we found that the air temperature over the supraglacial lake waved more gently than the others did and the surface lake water temperature varied with the temperature of the debris at a depth of 0.2-0.5 m. The absolute value of down vertical lapse rate of supraglacial lake is the smallest among the other topographical units of debris and debris-free ice, on Koxkar ablation zone, which reflect the surface heat conducted down through the lake water is more than that of the other two topographical units.