Geomorphic imprint of a small glacier and its rapid vanishing during 20th century: the Marmotte glacier (Ortles-Cevedale, Italy).

This work presents a glaciological and geomorphological study carried out on an area of three square kilometers in the southern part of the Ortles-Cevedale Group. In this area, at the head of the Val di Peio (Province of Trento), a small glacier existed until the first half of the 20th century, named Marmotte Glacier. This study was aimed at defining the maximum extent of the glacier during the Little Ice Age (LIA), reconstructing its fluctuations in the last century, and providing a geomorphological context through the compilation of a detailed geomorphological map, at the scale of 1:2500. A geomorphological survey was performed in the field, combining different survey techniques for establishing the transport history of glacigenic sediments and the relative age since deglaciation of rock surfaces. Historical glacier fluctuations have been reconstructed analysing historical sources, in particular old photos (aerial and oblique terrestrial photos) and glaciological observations started in the 1920s. During the LIA, the glacier extent was 0.33 km2, but already in the 1940s it was 40% smaller, and quickly become a glacieret by the end of the 1950s. In the following decades, the ice body went through a rapid fragmentation and completely vanished in the early 2000s. These results point to a high climatic sensitivity and high vulnerability for this small glacier, whose reconstructed equilibrium line altitude (ELA) matches very well with ELAs reconstructed for neighbouring glaciers in the LIA. This study provides evidence for significant marginal glaciation (i.e. the existence of very small glaciers and glacierets) during the LIA, in areas where geomorphological evidence is poorly expressed or even absent.