Assessing glacier surface reduction and recent climatic variations within small glacial catchments – The Fumo Valley case study (Southern Rhaetian Alps, Italy)

The assessment of climate change impacts within small Alpine catchments is essential for evaluating specific mitigation responses, predisposing environmental conservation strategies and planning a sustainable watershed management. In this study, glacier surface reduction from Little Ice Age to present and recent climatic variations were assessed in the Fumo Valley (Adamello Group, Southern Rhaetian Alps, Italy), which is a natural protected area with a high scientific-cultural value providing several ecosystem and socio-economic services (e.g., water resources for hydroelectric power generation). Sentinel-2 multispectral satellite images were used to elaborate a present-state glacier inventory through a combination of remote sensing techniques, which was compared to previous published glacier inventories in order to assess numerical and geometrical surface variations. Also, two temperature data series related to different thirty-years periods were analysed to assess air temperature variation. The results highlight a total surface loss of 5.99 km2 (-71.0%) from 1850 to 1958. Between 1958 and 2022 a total area reduction of 0.87 km2 (-35.5%) has been observed, which is comparable to other studies carried out at national scales. However, a marked progression phase has been observed between 1958 and 1981 (+76.3%), which is partially imputable to the glacial readvance episode occurred between the 1970s and the 1980s in the European Alps. After this phase, glaciers have been declined by 63.4% (1981-2022), with an accelerated regression phase between 2015 and 2022 (i.e., higher annual rate of variation, formation of ice-contact lakes, tongue separation and severe glacier fragmentation). The mean annual air temperature rose of 0.6°C between 1971-2000 and 1991-2020 periods, with a greater variation recorded for the mean annual maximum temperature (+1°C) if compared to the mean annual minimum temperature variation (+0.1°C) and a higher average temperature increase during spring and summer than in autumn and winter. The results of this study can be interpreted as clear indicators of the impact of climatic change on local scale, highlighting the vulnerability of the study area with respect of the predicted future climatic scenarios. The climate change impacts are expected to intensify in the next decades, with significant implications for hydrological cycle, geomorphological hazards, landscape evolution and ecosystems.