A031 Modeling and monitoring the Tortin alpine glacier by gravity and DGPS surveys 1 Pierrick CHASSERIAU PierVittorio RADOGNA Philippe LOGEAN Vincent LATTION and Raymond OLIVIER Institute of Geophysics. Geosciences & Environment Department. University of Lausanne. Switzerland Abstract Since many years a significant retreat of alpine glaciers is observed. Some of them located in tourist areas have a special interest for ski resorts facilities. That is the case of the 3000 meters high Tortin glacier located on north face of Mont Fort in the Valais state (Switzerland). Several surveys (gravimetry DGPS Georadar) have been carried out in the last years (2001-2005).