Recent evolution of the Vignemale glaciers (2013-2017)

Abstract

The glaciers of Ossoue, Petit Vignemale and Oulettes are the last three glaciers of the Vignemale massif. The largest one, Ossoue glacier, is also one of the best documented in the Pyrenees. Its evolution is an important proxy of the climatic variations in southwest Europe. The latest reconstruction of the glacier evolution spanned the 20th century up to 2013 (Marti et al., 2015a). Here we present an update of its mass balance between 2013 and 2017. An elevation change map was generated at 4 m resolution from two stereoscopic pairs, which were acquired by the Pléaides satellites system at the end of the summers 2013 and 2017. The elevation changes are similar to those that were routinely measured by the Moraine association at ablation stakes over the same period. In addition, the Pléiades data allow the estimation of the mass balance of Oulettes and Petit Vignemale glaciers, which are not equipped with stakes. We find that between 2013 and 2017, mass balance of the Ossoue, Oulettes and Petit Vignemale were respectively -5,2 +/- 0,5 m we, -4,0 +/- 0,9 m we and -4,2 +/- 0,9 m we. Pléiades data further indicate that the thinning rate in Ossoue glacier is higher in the center of the “Plateau des Neiges” (the upper part of the glacier), which can be explained by lower snow accumulation in winter.