L’evoluzione recente del glacialismo in Valle Aurina (Alpi Pusteresi) nelle immagini Landsat

Recent glacial evolution in Valle Aurina (Pusteresi Alps) by Landsat MSS images

Abstract

Information on the areal extent of glaciers and their fluctuations is obtainable through Landsat images by the different radiances of glacial surfaces with respect to unglaciated areas. The difference of radiance between the background and the glacial areas is maximum in those areas exposed to the sun. During the yearly glaciological surveys carried out since 1977 on some glacier fronts, considered as test areas, in Valle Aurina (Italian Pusteresi Alps), the ground radiance was measured at different points on the glaciers and boundary areas simultaneously with the passage of one of the Landsat satellites. The comparison between ground and remote sensed data allowed to extend the application of Landsat recorded data to those Valle Aurina glaciers which, because of unfavorable exposure conditions, appear undistinguishable from boundary areas upon a first examination. A comparison among the 1980, 1981 and 1983 maps shows frontal areas free of snows which gradually become more extensive between 1980 and 1983. In these three years, values computed from maps of glacier extent indicate an expansion in their surface of 0.137 km² between 1980-1981 and 0.561 km² between 1981 and 1983. The total increase in glacier extent is 0.698 km². Two opposite trends are distinguished within this positive fluctuation, i.e., larger glaciers are advancing and smaller ones are receding. Using opportune devices, the repeatability and extension of Landsat images allow to increase the ground observation data and to quantify the actual trend in progress.