Morphodynamics of the Mont Blanc glaciers and their recent evolution

The surface velocity of glaciers is a key parameter that provides fundamental information on glacier dynamics and their adaptation to changes in climate; moreover, ice velocity measurements are a very important parameter for modelling glacier physics and their evolution. While a few decades ago ice velocity would rely on point measurements performed in the field, the processing of high temporal and spatial resolution information from satellites nowadays provides new insights and a vast quantity of data, on a global scale, for the measurement of ice velocity. As of today, few studies have been performed in Alpine regions, and rarely has the focus been on ice velocity evolution. In the present study, we analyse the average monthly velocities on Alpine glaciers in the Mont Blanc massif. Seven years of Sentinel-2 optical satellite imagery have been processed to obtain ice velocity data. The main objectives of the study are: (i) to characterise the variability of the velocity fields of such glaciers, referring both to their temporal (seasonal and interannual) and spatial variations; (ii) to find relationships between the morphology of glaciers and their kinematics. We measured the monthly velocities of thirty glaciers varying from 18.0 m yr ^-1 to 436.3 m yr ^-1, highlighting a breakpoint in the trends in 2020. This led to the identification of 13 glaciers showing accelerations of more than 20.0 m yr ^-2 between 2020 and 2022 compared to previous years. We identified five clusters of morphodynamic characteristics, thus describing five different glacier type classes.