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Applying GPR and laser scanner techniques to monitor the Ossoue glacier (Pyrenees)

Abstract:

The Ossoue glacier in the Vignemale massif (3,298 m) is currently the longest and second largest of the Pyrenees (1,400-m length, 50-ha area), and the only one presenting glacier tongue morphology. We describe 50 MHz ground penetrating radar (GPR) and laser scanner surveys from which we assess the current state and dynamics of the glacier. In 2011, nearly 1,900 m of GPR profiles over the upper half of Ossoue glacier yielded up to 45 m of depth, an average value of 30 m thickness of the subglacial layer, and internal structure and layering. We compare the results with those from a study in 2006 of the same glacier, showing similar bedrock morphology with slightly less overall ice thickness than in 2011. Laser scanner surveys at the snout showed thinning rates of 3.32 m between 2010 and 2011, 4.15 m between 2011 and 2012, and an average loss of 7.47 m between 2010 and 2012. Present-day changes in Ossoue glacier are characterized by extensive thinning caused by melting and collapse of the ice mass. If these thinning rates are maintained, Ossoue glacier will vanish within 35 yr.