My research aims at observing and understanding the effect of climate change on mountain glaciers. Glacier wastage has a strong impact at the global scale by releasing freshwater in the oceans. Glaciers contribute about one third to a total sea level rise of 3 mm/year over the last 10-15 years. At the regional scale, they modify the salinity of the ocean. Mountain glaciers are also important for water resources. By studying glacier located in different areas (e.g. different latitudes), I want to better characterize the regional impact of climate change.
To monitor glacier evolution, I rely mostly on high resolution satellite optical images. The numerous in situ measurements available in the Mont-Blanc (French Alps) are useful to validate these new techniques. These ground data are available from the GLACIOCLIM program lead by C. Vincent (LGGE).
Satellite optical images are traditionally used to monitor variations in glacier areal extent. By producing muti-date Digital Elevation Models (DEM), we proved that they can also monitor their thickness changes [Berthier et al., 2004] . Such elevations changes are a first step toward the measurement of glacier mass balance. Avoiding biases in the DEMs as a function of elevation is a key issue. We recently observed significant biases in the SRTM topography that can lead to severe errors in the assessment of glacier elevation changes [Berthier et al., 2006b].
When optical images are well-coregistred and then correlated, they can monitor the surface velocities of mountain glaciers. SPOT5 images acquired a few weeks apart were used to monitor the surface velocity field of the glaciers in the Mont Blanc area [Berthier et al., 2005]. The advantage of this “reasonably” short time separation is that displacements are also measured in the accumulation area. When images are acquired one year apart, only the ablation area is observed. The same methodology, applied to images acquired with strong incidence angles can also measure vertical displacement of the Earth surface. We used this property to characterize the mass and energy balance of the Grimsvötn sublglacial lake in the middle of the Vatnajökull ice cap [Berthier et al., 2006a].
This work was mostly performed at the LEGOS in Toulouse. I also collaborate with Yves Arnaud from IRD, Christian Vincent from LGGE, Helgi Björnsson and his group at the University of Iceland University of Iceland. I am now post doc in the group of Garry Clarke at the EOS department of the University of Bristish Columbia.