| Summary: | Twelve years of observation at Austre Okstindbreen, Norway, have demonstrated that the drainage systems of glaciers change with time, both between and within seasons. Random events indicative of instability have been recorded, and disruption of the glacier systems has preceded some outbursts from Kalvtjorna, the glacier-dammed lake. The results of dye-tracer tests suggest that, although discrete systems exist within the glacier, these vary between years. They also demonstrate that some of the water entering the glacier is stored temporarily as the capacities of the systems change. The chemical composition of river water emerging from Austre Okstindbreen differs from year to year, and it is found that both systematic patterns of variation and random deviations from them occur. Although waters of different origin mix within drainage systems, not all systematic patterns of isotopic composition are eliminated by this mixture; diurnal variations are superimposed on longer-term trends, which sheds light on drainage conditions. Between-year differences of within-season trends probably reflect changing spatial patterns of drainage. -from Authors
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