The retreat of the Adamello Glacier (Italy) in a changing climate from snow and meteorological measurements, remote sensing observations and surface mass balance modelling

The Adamello Glacier, a rare example of a summit glacier in the Italian Alps, is undergoing profound transformations since the beginning of the century, with a substantial reduction in its surface area. Between 1995 and 2009, the net surface mass balance displayed an average decrease of -1439 mm w.e. per year. We analyze the retreat of the Adamello Glacier through diverse prospectives, discussing trends and variability in in-situ observations and remotely sensed images, and modelling its mass balance in the current and future climate. Firstly, we show the areal retreat of the glacierized area studied by means of satellite images (Landsat), obtaining an areal retreat of 11% every decade since 2007. Secondly, we present the timeseries of temperature and precipitation measured at nearby high elevation meteorological stations. Significant increasing trends are found in temperature, especially in the summer period (+0.8C every decade since 1996). Accumulation variability and trends are also discussed, drawing insights from snow water equivalent measurements systematically collected since 1967, revealing concerning spring trends with a 5-6% decrease in water equivalent every decade on April 1, and no significant trends in winter. Thirdly, by means of the Physical based Distributed Snow Land and Ice Model (PDSLIM), validated by ablation measurements collected in August 2023, we compute the distributed surface mass balance of the Adamello glacier for the period 2010-2023, obtaining an average net mass balance of -2170 mm w.e., significantly larger than in the period 1995-2009. Finally, in order to assess the future evolution of the glacier, we make use of regional climate models (RCMs) simulations of the future climate conditions developed in the framework of the CORDEX experiment for different emission scenarios. Our results highlight the critical conditions the Adamello Glacier is experiencing nowadays, quantifying the surface mass balance in the current climate, and estimate its expected behavior by the end of the century considering different emission scenarios.