Accelerated retreat of Italian Glaciers: the case of the Lobbia Glacier (Adamello Group, Rhaetian Alps)

Glaciers in the Italian Alps as well as in other regions are withdrawing due to the effects of global warming. As documented in most alpine regions, alpine glaciers reached their maximum Holocene extent during the Little Ice Age (LIA, around 1850 AD). In the Adamello-Presanella group (Rhaetian Alps) more than 140 glaciers developed during the LIA covering an area almost double compared to the present surface. Starting from the middle of the 19th century there was an important reduction in thickness and area of glacier bodies, broken by brief and weak advances, the most recent of which was around the 1980 AD. The Lobbia Glacier, a wide high-plateau glacier located in the Adamello Group, recorded in the last twenty years the fastest areal and volumetric variation since the end of the Little Ice Age. Trough multitemporal analisys of cartographic documents and aerial photos as well as geomorphological surveys, we reconstructed the glacier fluctuations in the last 150 years. Our data show that Lobbia Glacier experienced a relevant areal shrinking with a reduction of about 40% compared to its maximum Holocene extent as well as a frontal retreat of about 2350 m and 650 m of the northern and southern tongues respectively. Begging from the 1950s, we recorded a relevant contraction of the glacial body also in the highest portions of the accumulation area, highlighted by the formation of rocky windows, which are progressively widening. A relevant thinning of the glacier surface is also evidenced by hystorical photos of the First World War, showing a local thickness reduction of more than 80 m. The comparison between Digital Elevation Models confirms a consistent thickness reduction over the entire glacial body and documents a volumetric loss exceeding 60% from the LIA maximum to 2006 AD.