Late Holocene evolution of the Adamello Glacier (Rhaetian Alps): New insights for Alpine temperate glaciers

The Adamello Glacier is the largest and the thickest glacier in the Italian Alps, with a maximum ice thickness of 270 m. Here we provide an overview of its evolution since the Little Ice Age and of the results obtained from the ice core drilling activities carried out on this glacier. A review of the existing cartography from the 19th century onwards, surveys by the Italian Glaciological Committee, geomorphological studies and mass balance data are here combined to quantitatively describe the evolution of the Adamello Glacier from the Little Ice Age to the present day. Within this interval, the glacier has lost half of its surface, and its main front has receded by 2.8 km. Despite the rapid decline, in the last years ice cores were extracted from the former accumulation area of the glacier (Pian di Neve). In 2021, a 224 m-long ice core was drilled to bedrock. We also consider a previous ice core (ADA16), drilled in 2016 to the depth of 46 m. The analysis and inspection of these ice cores show that, despite the glacier consist of temperate ice and is subject to severe melting, some environmental signals are partially preserved in the ice stratigraphy, including visible layers related to Saharan dust transport and cryoconite. Using information from the upper layers of the glacier and a one-dimensional age-depth model, it was possible to estimate the age of the basal ice at approximately 2000 years ago. According to these preliminary results, the Adamello Glacier, despite being a temperate glacier and being subject to heavy melting during summer, is still able to preserve, at least partially, signals that are suitable to construct climatic and environmental records. This implies that, contrary to the previous view, environmental records can be obtained from ice cores drilled at temperate glaciers subject to melting. In the context of climate change, this is a relevant result with important implications for paleoclimatic and environmental reconstructions.