The valley glaciers of the Italian Eastern Alps may survive beyond this century?

A recent work (Serandrei-Barbero et al, 2019) carried out on the Western Tauri glaciers (Eastern Alps), shows, to the end of this century, glacier length reductions between 20% and 35% for valley glaciers and between 30% and 60% for mountain glaciers, representing 95% of the Italian Alps glaciers. Their consequent surface area loss of more than 60%, with a probable fragmentation in smaller units, leads to the possibility that 95% of the living glaciers will disappear by the end of this century. These results were obtained by a linear model (Leclercq and Oerlemans, 2012, Zecchetto et al., 2017) forced by the temperature increase according to the A1B scenario (Nakicenovic et al., 2000), which indicates an increase of temperature of 0.25° C per decade until the mid of the 21st century and of 0.36° C per decade in the second half of the century. These temperature projections have been used by Gobiet et al., 2014 for their analysis of the future climate change in the European Alps. To extend this analysis to other valley glaciers of the Italian Eastern Alps, we have used the same linear model to investigate the behaviour of seven valley glaciers, pertaining to South Tirol, as a result of the same temperature expected by the A1B scenario. To six glaciers, the only ones considered as valley glaciers in the Nuovo Catasto dei Ghiacciai Italiani (Smiraglia and Diolaiuti, 2015), we added the Lana glacier, a typical complex valley glacier with a tongue derived from the confluence of three different accumulation basins, the fourth one being now suspended on the tongue that feeds with collapses and avalanches. In 1980, the areas of these 7 glaciers were between 6,5 km2 and 1,7 km2, in 2008 between 5,5 km2 and 1.3 km2. In 1980 the lengths of these glaciers were between 4200 m and 2900 m, in 2016 between 4035 m and 2585 m with percent shortenings between 4% and 25%. The results show that the valley glaciers experience lower retreat rates than those of the mountain glaciers. These results have to be considered as a lower bound value since progressive glacier shrinkage and fragmentation will lead to increasing glacier melt even under the same climatic conditions because glacier dynamics and response times cause a condition of glacier disequilibrium. Despite this, and given the measured and modeled retreats, the valley glaciers seem to be the only glaciers possibly reaching the next century.