A new method was developed to estimate the mass balance in unsampled areas from existing datasets. Three years of mass-balance data from two glaciers in the central Italian Alps were used to develop and test a multiple-regression method based exclusively on a 10m resolution digital terrain model. The introduction of a relative elevation attribute, which expresses the degree of wind exposure of the gridcells, notably increased the amount of explainable variance in winter balance with respect to altitude itself. The summer balance is highly correlated with elevation, but, in order to obtain reliable extrapolations, the clear-sky shortwave radiation and the diurnal cloud-cover cycle had to be taken into account. The net annual mass balance on a glacier system comprising the two monitored glaciers was calculated by applying both a single regression of winter and summer balance with altitude and the new regression method. The consistency of results was assessed against measured net balances and snow-cover maps drawn in the ablation season. The results of the new method were in close agreement with observations and proved to be less sensitive to the spatial representation of the sampled areas.

Glaciers have an important hydrological buffering effect, but their current rapid reduction raises concerns about future water availability and management. This work presents a hydrological sensitivity analysis to different climatic and glacier cover conditions, carried out over four catchments with area between 8 and 1050 km², and with glacierization between 2% and 70%, in the Italian Alps. The analysis is based on past observations, and exploits a unique dataset of glacier change and hydro-meteorological data. The working approach is aimed at avoiding uncertainties typical of future runoff projections in glacierized catchments. The results highlight a transition from glacial to nival hydrological regime, with the highest impacts in August runoff over smaller catchments. The buffering effect of current glaciers has largely decreased if compared to the Little Ice Age, up to 75% for larger catchments, but it is still important during warm and dry summers like 2003. We confirm a non-linear relationship between glacier contribution in late summer and catchment area/percent glacierization. The peak in runoff attributable to glacier melt, expected in the next 2–3 decades on highly glacierized alpine catchments, has already passed in the study area.

The response of very small glaciers to climate changes is highly scattered and little known in comparison with larger ice bodies. In particular, small avalanche-fed and debris-covered glaciers lack mass balance series of sufficient length. In this paper we present 13 years of high-resolution observations over the Occidentale del Montasio Glacier, collected using Airborne Laser Scanning, Terrestrial Laser Scanning, and Structure from Motion Multi-View Stereo techniques for monitoring its geodetic mass balance and surface dynamics. The results have been analyzed jointly with meteorological variables, and compared to a sample of “reference” glaciers for the European Alps. From 2006 to 2019 the mass balance showed high interannual variability and an average rate much closer to zero than the average of the Alpine reference glaciers (−0.09 vs. −1.42 m water equivalent per year, respectively). This behavior can be explained by the high correlation between annual balance and solid precipitation, which displayed recent peaks. The air temperature is not significantly correlated with the mass balance, which is main controlled by avalanche activity, shadowing and debris cover. However, its rapid increase is progressively reducing the fraction of solid precipitation, and increasing the length of the ablation season.