I ghiacciai delle Alpi Pusteresi nell'ultimo ventennio: modalità e cause del regresso

The Pusteresi Alps glaciers in the last twenty years: modality and cause of retreat

Abstract

The Pusteresi Alps glaciers were identified and classified using Landsat TM images of September 1985, 1987, 1989 and 1991. The technique to identify glacier surfaces is based on a statistical classifier, which integrates remote sensed data with those from the digital terrain model. Surface values obtained concern all glaciers within the studied area independent of their dimension. They quantify the loss in glacier surface verified between 1985 and 1991 and indicate that in 1991, after the discordant trends evidenced in 1987 and 1989, the retreat was extended to all existing glaciers in the examined area. Frontal measurements made since 1977 till present show a prevailing retreat of the glacier snouts from 1983 and a more intensified retreating since 1991. The utilisation of results obtained by these different approaches and their comparison with the trend of temperature and precipitation data recorded at Predoi (1449 m) since 1977 allow to show temperature increases in 1986-87 as the main factor controlling snouts with a response time around 5 years; while the recent, progressive increase of glacier retreat is due to the scarcity of winter precipitations and their further decrease from 1988.