282 
DETERMINATION AND SIGNIFICANCE OF SNOW BOUNDARIES ON 
GLACIERS 
Harold Haefner 
Remote Sensing Laboratories, Department of Geography 
University of Zurich-Irchel 
Zurich, Switzerland 
ABSTRACT 
The seasonal variation of the snow accumulation and melting process in its regional or global 
context has its tremendeous economical and ecological impacts. It not only affects the run-off 
pattern and the water balance but as well changes the albedo, which again feedbacks on the 
radiation budget of the earth and ultimately on the climate. Adequate remote sensing methods have 
been developed to map and monitor the areal dynamics of the snowcover during the last years. Of 
specific interest today are the conditions of the snowcover on the surface of glaciers in mountainous 
regions. Here the accumulation and melting pattern of the snow strongly influences the energy and 
mass balance of the glaciers and consequently its run-off regime. Alterations of the weather 
conditions have a direct impact on this process. Or in reverse, by monitoring the melting process it 
becomes possible to deduce changes of weather, and in the long run of the climate. 
An extensive and longterm project has been established by the Department of Geography, 
University of Zurich, to develop the methodology for a careful and accurate monitoring of the 
various boundaries such as transient snowline, annual snowline, fimline, equlibrium line etc. and 
the deduction of the two most important glacial indices ELA and AAR. Only a thourough 
understanding of the glaciological terminology, the use of satellite data from the adequate season 
and appropriate techniques allow to derive significant, comparable results. 
The method is based on the establishment of a relationship between the directly detectable 
boundaries and the equilibrium line as basis for the assessment of the ELA. To monitor the AAR, 
the total surface of the glacier has to be measured periodically with great accuracy. 
First results of the project include a detailed study of the migration of the snowlines on the Aletsch 
Glacier during one melting period, the derivation of the corresponding melting curve, and a 
comparative assessment of the annual snowline and the ELA on three different glaciers for four 
successive seasons. 
KEYWORDS 
glacier, snowline, fimline, equilibrium line altitude, accumulation area ratio, melting curve, climatic 
change, high-resolution satellite data