Last decades of ice loss in the small glaciers of the S-E Italian Alps

Small Alpine glaciers located below the regional equilibrium line altitude are experiencing considerable ice loss and are expected to fragment into smaller glacial bodies and eventually disappear. Monitoring such glaciers by satellite remote sensing is often challenging because their size and surrounding topography are incompatible with the current spatial resolution of non-commercial satellites. One of the regions where these challenges are most apparent, and where long-term glacier mass balance data are scarce, are the south-eastern Italian Alps. Here, spread between the Dolomites and the Julian Alps, there are still 13 small glaciers and a few dozen of glacierets and ice patches, along with several permanent snow patches. This study presents a multi-decadal (1980s–2020s) estimation of surface elevation change and geodetic mass balance of current mountain glaciers present in the area, along with a few ice patches. Calculations are based on geodetic data: high resolution and accuracy are obtained with uncrewed aerial vehicle (UAV), structure from motion (SfM), and airborne light detection and ranging (lidar) methods. SfM on historical aerial imagery has been used for oldest decades, with a focus on the Dolomites area. Recent changes in the smaller ice bodies of the Julian Alps have been less pronounced, owing to favorable topography and the positive feedback from years with extreme snow accumulation. Overall, small glaciers of the southeastern Italian alps show a less negative geodetic mass balance than the mass balance of the reference Alpine glaciers. Most of the volume loss is related to the Marmolada glacier alone. The different rates of ice loss suggest that the feedback mechanisms and the role of debris cover in the final stages of the evolution of these glaciers should be further investigated.