Dynamics and mass balance of mountain glaciers (Alps, Iceland, Himalaya). Contribution of satellite imagery

In a context of fast glacier retreat, a continuous and global monitoring of mountain glaciers is required but cannot be achieved thanks to ground measurements. In this thesis, we demonstrate that high resolution satellite optical images permit to observe the dynamic and volumetric evolutions of glaciers. Our methods are first validated over the well-surveved glaciers in the Alps and then applied to remote and larger ice masses. For most Mont Blanc glaciers, thinning is enhanced in the ablation area during the last 10 years whereas, at higher elevation, no significant thickness change is detected. A similar signal is also observed in Himalaya and Iceland. Melting of glaciers in these 2 later regions may have raised global sea level by up to 0.13 mm/year in the last 5 years. Surface velocities of Mont Blanc glaciers (Alps) show short term (summer) fluctuations that are connected to the intensity of surface melting and likely changes of the subglacial hydrological network during the 2003 heat wave. A significant slow down (30 to 40% in 20 years) of the Mer de Glace suggests that glacier dynamics play an important role in the recent thinning of the lower part of this glacier