ABSTRACT

The area of a glacier is a basic property in a glacier inventory that is frequently used for upscaling of only locally available information to large ensembles of glaciers (e.g. size dependent calculations of overall area change or sea level rise). The land surface area covered by glaciers and ice caps is also an important boundary condition for climate models that calculate the energy fluxes according to the surface type. As the globally available data sets of glacier covered area are either not complete or very rough, new initiatives like Global Land Ice Measurements from Space (GLIMS) have started to compile a global glacier inventory (location, size, digital outlines) from satellite data. Glacier area change (percent per year) could be compared on a global scale to quantify regional climate change effects. However, glacier-specific changes could only be determined when the same entities are compared. This is quite troublesome when only the point information from the formerWorldGlacier Inventory (WGI) is available. Glacier area changes as obtained from satellite data over large regions do also help to assess the representativeness of the sparser sample of field-based length change and mass balance measurements or to identify what else is going on (Haeberli et al. 2007). For example, it is possible to observe whether the change is restricted to the glacier terminus or if a glacier with a stagnant tongue is really in a good health. In the European Alps, such downwasting (i.e. stationary thinning) and disintegrating glaciers with little change at the terminus could be observed widely using spaceborne sensors (Paul et al. 2007). In the sections below, various ways of qualitative and quantitative area change assessment and visualisation are described. Thereby, Landsat is in general used as a synonym for Landsat-type satellites that have similar spatial resolution and spectral bands.