KASER G., ZINGERLE C., OBERSCHMIED C. & MUNARI M.
An Exceptionally negative mass-balance of a small alpine glacier – Un bilancio di massa eccezionalmente negativo di un piccolo ghiacciaio alpino
Pages 99-102
Abstract
On Wei~brunnfemeriGhiacciaio di Fontana Bianca in the OrtlesCevedale group, mass balance studies have been made since 1983/84 with a three year interruption. In 1997/98, the mass balance reached its negative record with -1610 kg rn”", being about 1.5 times the former record. Neither the temperature recorded at nearby weather stations, nor particular accumulation deficits can offer an explanation for the exceptional process. Yet, compared to the other years, the vertical mass balance profile was markedly different, indicating distinctly increased ablation in the glaciers’ higher zones. This can be explained by the consumption of almost the entire fim body over the last several years when the annual equilibrium line remained above the highest peaks. As a consequence, dust, accumulated over many years, became concentrated on an impermeable layer, changing the surface albedo distinctly. The lack of summer snowfall may be an additional reason for increased ablation. A 0.1 to 0.15 decrease in albedo can explain the increased ablation in the former firn zone of the glacier. Such sudden changes of surface properties can be expected during any period of strong glacier retreat and can lead to markedly wrong conclusions when deducing a previous climate from glacier fluctuations.