Recent glacier changes and related contribution potential to river discharge in the Vinschau/Val Venosta, Italian Alps

Abstract

Recent glacier changes in the Vinschgau / Val Venosta region of the Autonomous Province of Bozen / Bolzano, Northern Italy, were quantified using high resolution multi-temporal airborne laser scanning data (fall 2005 to fall 2013). The analysis reveals a marked reduction in glacier area (-14.6 %), mean surface elevation (-7.1 m) and mass (-388 ± 26 % 10₉ kg) during the study period. Observed values of relative area change and mean changes in surface elevation are similar in the Ötztal Alps and the Texel Group in the North and the Ortler-Cevedale Group in the South of the study region.The mass balance record of Langenferner / Vedretta Lunga, a well measured glacier within the study region, was analyzed in terms of its representativeness for glacier changes in the wider region. The inter-annual variability of the mass balance signal was investigated by comparing the results to those of other monitored glaciers in the Eastern Alps and the magnitude of the geodetically derived mass change of the glacier was compared to the mass change of all other 91 glaciers within the study region. Results show that Langenferner / Vedretta Lunga over all satisfactorily represents the temporal variability of regional glacier mass changes, but values for the mass balance in certain years request further analysis. Furthermore, the glacier displays one of the most negative values of geodetic mass balance within the study region. Finally, a first order quantification of glacier melt contribution to total river discharge in the study area is provided which reveals that the annual contribution of excess melt due to glacier retreat amounts to 4.6 % of total river discharge, while values for single years can reach 9 %. During the months July to September, the contribution of glacier melt to total runoff can be in the order of 25 % in single years.