Abstract ID: 28.7372 | Accepted as Talk | Talk | 2025-02-27 11:15 - 11:30 | Ágnes‐Heller‐Haus/Small Lecture Room

The equilibrium line altitude (ELA), which demarks the separation between the accumulation and ablation areas of a glacier at the end of the summer, is a critical control of the glacier mass balance. Unfortunately, sparse and limited information exists for reconstructing past ELA fluctuations before systematic mass balance observations. The Ortles-Cevedale Group in the Italian Alps is a lucky exception, as it benefits from an extensive photographic record throughout the 20th century, which documents the late-summer snowline conditions on the glaciers. Photographic material is available starting from World War I (1915-1918) and is enriched by the monograph of Ardito Desio (I Ghiacciai del gruppo Ortles-Cevedale,1967) and by the observation of the Italian Glaciological Committee (CGI) and of the Servizio Glaciologico Lombardo (SGL). This study focuses on the reconstruction of late-summer snowline fluctuations in the Ortles-Cevedale Group by combining historical photographs and maps, digital elevation models (DEMs) and GIS-based techniques. For the most recent decades, satellite imagery (Landsat, Sentinel-2, PlanetScope) complements the available terrestrial oblique photographs, providing a more comprehensive and detailed dataset. The results highlight a pronounced interannual variability in the late-summer snowline elevation, with consistent interdecadal variations on the order of 200–300 meters. There is also significant spatial variability influenced by glacier aspect, snow input mechanisms (direct accumulation or avalanching) and the effects of topographic shading. Glacier surface topography changed dramatically in the last century, and surface lowering locally exceeded 100 meters. This is a key aspect that has to be considered for accurate estimations of snowline altitudes. By integrating historical materials and modern satellite imagery, this rare long-term dataset will improve our understanding of past climatic fluctuations and their effects on glacier dynamics, providing insights on the ELA and glacier sensitivity to the ongoing atmospheric warming.