Le variazioni biennali di superficie dei ghiacciai delle Alpi Breonie, Aurine e Pusteresi nei dai Landsat TM del 13 Settembre 1987

Biennal surface variations of the Breonie, Aurine and Pusteresi Glaciers (Eastern Alps) in Landsat TM data of 13 September 1987

Abstract

With the aim of making a temporal comparison among data acquired using the same technique, the glacier surfaces of the Breonie, Aurine and Pusteresi Alps were obtained from the Landsat TM data of 13 September 1987. Of the one hundred Italian glaciers included in the considered image, 159 of them do not appear in the image because of cloud cover or due to a slipping of the image towards the East. For 74 glaciers it was possible to compare the extension of their surfaces with the 1985 values. The comparison clearly shows a marked decrease in glacierized or snow-covered areas. This is in agreement with the ground data collected which indicate 1987 as a year of exceptional ablation and such to bring about the disappearance of numerous glacierets; 15 of these, in fact, do not appear in the image of 13 September, 1987. The results are discussed for the different Alpine sectors and, where possible, the data obtained are compared with field observations or analyzed in detail by extraction of glacier boundaries in the two years considered. The decreasing is less for the larger glaciers; decreases sometimes very pronounced regard either small glaciers located below the yearly snow line or snow glacierets first described in the 1982 Inventory. Due to the extension of the considered area, the analysis used a low cost methodology which, even if not using the digital elevation model, gave quantitative synoptic data for 89 Alpine glaciers.