藏东南嘎隆拉冰川表碛冻融过程与零点幕效应

The process of freezing and thawing and the zero curtain effect of debris-covered area of the Galongla Glacier in the southeastern Tibetan Plateau

冰川表碛区冻融过程的观测分析有助于厘清各层之间能量和水分传输的关系,从而为构建相应的能量平衡模型以及冰川径流模型提供理论支持。基于2015年10月至2016年11月嘎隆拉冰川表碛区自动气象站气象资料,对表碛区冻融过程进行分析,结果表明:表碛中出现冻土中常见的秋季和春季零点幕效应,秋季零点幕持续时间32天,春季零点幕持续58天;春季零点幕期间,气温和地表温度均呈现清晨低,午后高的日变化特征,而表碛层内温度没有明显的日变化特征,其体积含水率呈"脉冲式"变化;春季零点幕效应结束,底层冻结层破坏后,冰川冰消融才开始;嘎隆拉冰川表碛对冰川冰消融的影响不仅是因为表碛较厚,在消融量上抑制了冰川冰的消融,而且更重要的是表碛产生零点幕效应,延迟了表碛下冰川冰开始消融的日期,在时间上抑制了冰川冰消融。

Observation and analysis of the freezing-thawing process in debris-covered area of a glacier play an important role in understanding the energy and water transfer relationship between debris-covered layers. Based on the meteorological data from automatic meteorological station in debris-covered area of the Galongla Glacier from October 2015 to November 2016, the freezing-thawing processes of the debris-covered area were analyzed. The zero curtain effects in autumn and spring, which usually occur in frozen soil, are found in debris-covered area, which lasts for 32 days in autumn and 58 days in spring. The diurnal variation characteristics with low values in morning and high values in afternoon of average temperature and the surface temperature during the spring zero curtain period were presented, while the temperature in the debris layer had no obvious diurnal variation, and the volume water content showed an impulse. At the end of the zero-curtain effect in spring, the destruction of the underlying frozen layer and the ablation of glacier ice began. The effect of debris cover of the Galongla glacier on glacial ice ablation was not only because of the thicker debris cover which inhibits the ablation quantity of glacial ice, but also because that the starting date of glacial ice ablation delayed when the zero curtain effect produced in debris cover.