Structural phase changes of the liquid water component in Alpine snow

摘要

The arrangement of free water in the complex texture of Alpine snow was measured by different methods: broadband electro-magnetic measurements ranging from radio frequencies up to the microwave K-Band regime directly allow the detection of the geometrical structure of the water bodies; hydraulic measurements―measurements of water percolation through or water drainage off an Alpine snow cover―show a significant change of water movement characteristics which are caused by changes in the water geometrical configuration (structural phase changes) due to the natural variation in the free water saturation. Structural characteristics of water bodies included in snow are reflected by the dielectric depolarization factors. The special case of ring-shaped water inclusions is reflected by the magnetic permeability. Field measurements were carried out in the Stubai Alps, Austria. Metamorphism of these Alpine snow covers was characterized by several melt-freeze cycles. Four main regimes of water saturation existed, each characterized by different structural properties of the free water bodies: the pendular zone with closed isolated water bodies, a funicular zone with confluent water bodies, a transitional zone where isolated water bodies begin to merge and a sub-regime included in the pendular zone characterized by the existence of ring-shaped water bodies. Experimental results of a 12-year field study are presented.