Modificazioni volumetriche sul Ghiacciaio del Caresèr (Alpi Centrali, Gruppo Ortles-Cevedale) tra il 1967 e il 1980

The variations in volume of the Caresèr Glacier (Central Alps – Ortles-Cevedale Group) between 1967 and 1980

Abstract

The variations in volume of the Caresèr Glacier (Ortles-Cevedale Group) over a period of 14 years were determined by means of comparison of two aerial surveys, taken in 1967 and 1980. The data used for computer processing were altitude values (obtained by evaluation of aerial photographs) on the nodes of a 50 m grid. Two homogeneous groups of digital data on the surface of the glacier were thus obtained, for both surveys. The point-by-point differences of the digital models gave a matrix of altitude variations, which in turn gave respectively the increases (net accumulation) and losses (net ablation) of the glacier mass in terms of thickness (m) and volume (m3). The same matrix also provided isovariation curves, allowing the surface to be subdivided into belts representing level variations and, lastly, representation of the phenomena in the form of a thematic map (pl. 1). The availability of data on the balance of the glacier, calculated by means of direct surveys, also allowed a comparison of the two methodologies. The data compared, expressed as water thickness and water volumes (table 1) for the whole surface of the glacier, with the exception of the inaccessible summit area (above 3 200 m a.s.l.), show good correspondence, with an overall difference in evaluation of 0,41 m of water, equal to 13,5 %, for the whole period 1967- 1980.