Dynamics of equilibrium line altitude in glaciers of the Monte Rosa massif in the Alps derived from Sentinel-2 satellite images

The equilibrium line altitude (ELA) is an immediate indicator of the mass balance of glaciers. The evolution of the ELA of four major glaciers in the Monte Rosa (European Alps) massif was investigated in this study. We used Sentinel-2 satellite images to derive the end-of-summer snowline altitude (SLA) as an approximation of ELA considering the fluctuations in the snowline at the end of the ablation season (from August to mid-October in 2016–2023). SLA was estimated as a percentile of the histogram of the DEM of each glacier with the applied snow-mask, based on the normalised difference snow index (NDSI). ELA was determined as the maximum snowline elevation reached in the season. We found the mean ELA for the studied period as 3560, 3230, 3430 and 3570 m above the sea level for Gornergletscher, Belvedere Glacier, Grenzgletscher, and Lys Glacier respectively. These differences are likely due to the variation in slope orientation and amount of snow accumulation. An increase in ELA was found for all the glaciers in the studied period amounting to 22.7, 8.3, 33.1 and 27.0 m/y respectively. The pattern of temporal behaviour was similar for all the glaciers, although we expected a different behaviour of the Belvedere Glacier, which is characterized by various local effects, such as frequent avalanching and rough topography.