Relation entre les bilans de masse de la Sforzellina et ceux des autres glaciers en Europe. Influence des facteurs localisation géographique et taille du glacier

Abstract

The data about 15 years of mass balance of Sforzellina Glacier (Lombardy Alps, Italy) were analysed ; the mass balance data were constantly negatives from 1987 to 2000 and positive only in 2001. The mass balance data of Sforzellina Glacier represents a good statistical sample that was compared with data of other Alpine glaciers (Careser (1), Hintereisfemer (A), Vernagh (A), Sarennes (F), Saint Sorlin (F) Gries (S), Kesselvand (S), Aletsch (S), Wurten (A)). The study about the relations between glacier mass balance data allowed to analyze the temporal variability of alpine mass balances, evidencing past and present glacial trend, moreover evidenced the sensibility of this glaciological parameter that encloses not only a temporal index of climate variability but also a spatial determination of the climate variability. In this way it was possible to characterize a regionalism of glacier mass balances that allows the mapping of the climate and of its spatial and temporal variations. The study of spatial and dimensional relations of Alpine glaciers in the period 1967-1997 and 1987-1998 evidenced that the correlation between the mass balance series decreases if the distance between the studied glacier increases (according to exponential function if we consider emispheric mass balance data, according to linear function if we use only italian data) and contemporaly the standard deviation of the predicted data increases if the distance from glacier used to predict the data increases. From the experimental data it is possible to assert that the critical distance beyond which the correlation between the Italian glacier mass balances and the others is not meaningful (r < 0.5) is about 200 km. Within such spatial range, instead, the correlations with the series of mass balance data were meaningful. This distance can be interpreted as the limit of the region introduced previously. In this way was possible to quantify and to map the comparability zone of Italian glaciers. If we consider the other Alpine glaciers, the comparability zones are in some cases more extended (350 km for Hintereisferner) even if the mean value is about 200 km. Moreover the dimensional influences on the single mass balance and on the relations between the different glaciers turned out negligible. It is possible to conclude that in order to reconstruct mass balance data using a modelistic method it is necessary to employ data of close glaciers (with a maximum spatial range of 200 km) whi!e the dimensional factor does not seem important; that is to say that on the Alps also the small glaciers (as Sforzellina Glacier) can be compared with large glacier having good results if they are in a spatial range of 200 km. This result is important to use the limited series of mass balance data currently available in order to reconstruct past and present mass balance of other alpine glaciers that are not directly monitored. The study supplies moreover suggestions on spatial distribution of glaciers to measure directly.