Applicazione di tecniche remote sensing per lo studio dell'evoluzione e della dinamica criosferica in aree remote e di alta quota

Glaciers are sensitive climate indicators because they adjust their size in response to changes in climate (e.g. temperature and precipitation). The attention paid by the scientists to mountain glacier change is increasing as there are robust evidence of a global glacier shrinkage over the past five decades, which in turn is the consequence of global warming. Understanding the glacier response to climate change is of tremendous importance not only for improving scientific knowledge, but also to predict and manage water resources and natural risks for the people living in mountain areas in the short (e.g. glacier lake outburst floods), and long term (e.g. droughts).
In this thesis are analysed different cryospheric elements (mainly glaciers and snow coverage) to describe their recent evolution and to look for relations, if any, with climate trends.
Firstly, the focus is put on the Karakoram glaciers. Although a general worldwide retreat of mountain glaciers has been acknowledged by the scientific community, the Karakoram region represents an exception in this sense. Indeed, the net mass balance of the glaciers here in the early twenty-first century was slightly positive, and even some are expanding and thickening. This anomalous behaviour is known as Karakoram Anomaly.
More precisely the study area is the Central Karakoram National Park (CKNP), a protected national park in Northern Pakistan representative of the glaciation of the whole Karakoram Range. The westerlies represent the dominant wind system and they occur during winter, while the neighbour Himalayan region is mainly influenced by the summer moonson. A comprehensive description of the state of the CKNP glaciers and of their recent evolution is presented. This was made after the compilation of the glacier inventory of the park for the years 2001 and 2010, which is also presented. Moreover, the analysis of the regional climate change in the recent years is also discussed and related to the actual glacier change, in order to understand the causes behind the Karakoram Anomaly. The glacier area change of the 711 glaciers mapped in the study zone during 2001–2010 was only -0.4 ± 202.9 km2 (over 4605.9 ± 86.1 km2 in 2001), evidencing a general stability. The climate analysis supports glacier stability in the area. A slight increase in late summer snow cover area during 2001–2010 was observed from MODIS snow data. At the same time, the available weather stations revealed an increase of snowfall events and a decrease of mean summer air temperatures since 1980, which would translate into more persistent snow cover during the melt season. These results support an enhanced glacier preservation in the ablation areas due to a long-lasting snow cover, and stronger accumulation at higher altitudes, pushing towards positive net balances.
The other major aim of the present work is to provide a simple model to evaluate ice melt at the glacier surface. As the supraglacial-debris cover can alter ice ablation close to the glacier surface depending on its thickness, the model was made up of two parts: one which computes the ice melt over the bare ice areas using an enhanced T-index formula; and one for the debris-covered areas using a conductive heat flux module. For the debris-covered parts, the debris thickness map is produced and then provided to the model as input for the computation, other than the distributed shortwave incoming radiation. For the bare ice areas, the modeled air temperature and shortwave incoming radiation are derived from the automatic weather stations present in the CKNP and given to the model. The other model requirement is the digital elevation model. In particular, the meteorological input data were distributed starting from data acquired at Askole automatic