Parametri climatici e variazioni glaciali nel periodo 1950-1982

Climatic parameters and glacial fluctuations in the period 1950-1982

Abstract

The present work analyses the data of snout fluctuations of about 60 Italian glaciers, among about 150 checked every year. Data processing allowed calculation and analysis of the linear regressions of 28 glaciers which have shown a higher level of reliability. These regressions give the annual average advancements, related to some morphological and climatic parameters of the glaciers themselves. Consequently, glacier advance mainly depends on the altitude of their highest point, on the differences in altitude between this point and the snout, and on the glacier surface. In order to compare climatic parameters, the number of glaciers was further reduced to 20, on the basis of the significance levels of the correlations existing among the snout displacements. Numerical analysis was then carried out of the variations in average temperatures in the period May-September of every year and of the amount of precipitation in the period October-May between every two years, in relation to the average values of a period preceding the 30 years considered. Data came from 12 meteorological stations distributed all over the Italian Alps. Correlations among three variables were then determined by calculating the linear multiple regressions of snout fluctuations depending on thermic and pluviometric differences. The delay between superimposed climatic factors and snout fluctuations was thus determined, turning out to be 8 years on average. It was also ascertained that the delay due to thermic causes was 6 years on average and that due to pluviometric causes 11 years on average. The contemporaneous effect of the decrease by 1° C of the average temperature in the period May-September and of the increase by 100 mm of precipitation in the period October-May was then calculated, and an average value of 16 m advance was found. Lastly, numerical analysis showed that advancement for climatic reasons was related to the glacier surface and that it increases according to a linear regression. Instead, it decreases, again according to a linear regression, in relation to orientation evaluated anti-clockwise from North to North-East.