Multitemporal glaciers inventory of the Italian Alps, a basic tool for reconstructing the ongoing climate change

Mountain glaciers are very sensitive environmental indicators as they react to climatic changes, in particular summer temperature and winter precipitation rate, modifying their size and shape as a conseguence of variation on their mass balance. Since the end of the maximum Holocene advance, occured during the Little Ice Age in the first half of the 19th Century, the Alps experienced a general glaciers shrinkage particularly vigorous over the last decades. The availability of accurate quantitative measurements of glaciological parameters is the base to better understand and define the relationship between glaciers variations and climatic changes. Datasets on glacier areal variations furnish clear evidence that glaciers retreat is widespread along the whole Alpine chain and shrinkage was accelerated during the last decades. Glacier inventories represent relevant tools that allow the quantification of glaciers extension and volume and to estimate the impacts of glacier changes on the availability of water resources as well as on the progressive widening of paraglacial environment. Here we present multitemporal dataset that outline the state of Italian glaciers during different hydrological periods (1957-1958, 1988-1989, 2006-2007, 2014-2015), realized in the framework of the Nextdata Project. Our aim is to improve the knowledge of the Italian glacial resource through the creation of a dynamic and updateable quantitative inventory. The updated multitemporal picture of the glacial resource in the Italian Alps is being realized through the acquisition of the most up to date available information on glaciers, taking into account the existing international standards adopted in glaciological studies. Glaciers outlines were detected by the interpretation of new generation of orthorectified aerial photos at high geometric resolution available through the Web Map Service provided by national and local Geoportal. Glacial bodies outlines were manually digitized from high-resolution aerial ortophotographs in GIS environment, for mapping glaciers as polygons in the vector domain. Alpha- numeric attribute table associated with the glacier outline retains the main morphometric glaciological parameters (area, maximum length, width, slope, max and min elevation, aspect, latitude and longitude of the glacier centroid) according to the World Glacier Monitoring Service (WGMS) guidelines for the compilation of glacier inventory data from digital sources. Furthermore, each attribute table contains inventory number and glaciers names according to the previous Inventory of Italian Glacier (CGI-CNR, 1959, 1961a, 1961b, 1962), as well as the identification (ID) according to the hydrological coding suggested by the WGMS (1989). The data derived from the multitemporal analysis allow to quantify the progressive and dramatic mass loss experienced by Italian glaciers since the last three decades. The glaciers decline is underlined by diffused extinction of smaller bodies, by the fragmentation of wider glaciers and by remarkable reduction of thickness also in the accumulation area.