Assigned Session: FS 3.148: Glacier and permafrost risks in a changing climate
Unveiling permafrost in the Pyrenees
Abstract ID: 3.12640 | Accepted as Poster | Poster | TBA | TBA
Julia Garcia-Oteyza (1)
Marc Oliva (2), Josep Ventura (2), Claudia Pérez (2), Anna Echevarría (3), Magalí Delmas (4), Marcelo Fernandes (5), Florence Magnin (6), Benjamin Lehmann (7), Pierre Valla (7), Valentí Turu (8), Xavier Ros (8)
(2) Department of Geography, Universitat de Barcelona, Barcelona, Catalonia, Spain
(3) Andorra Recerca+Innovació, Sant Julià de Lòria, Andorra
(4) CNRS, MNHN, HNHP, Université de Perpignan Via Domitia, Perpignan, France
(5) entre for Geographical Studies-IGOT, Universidade de Lisboa, Lisboa, Portugal,
(6) Laboratoire EDYTE M, CNRS/Université Savoie Mont-Blanc, Le Bourget-du-Lac, France
(7) CNRS, IRD, IFSTTAR, ISTerre, Université Grenoble Alpes, Grenoble, France
(8) Igeotest, Carrer Dr. Nequi 4, 1er-3a Andorra la Vella AD500, Principat d’Andorra
The Pyrenees, a mountain range in southern Europe with a maximum elevation of 3404 m, are experiencing rapid transformations in their cryosphere driven by recent warming. The permafrost, a crucial component of the Pyrenean high mountains, is undergoing significant changes, although its response remains insufficiently studied despite associated hazards occurring in recent years, such as rockfalls and moraine collapses. Currently, the mean annual air temperature (MAAT) is located between 2950-3000 m altitude. Probable permafrost is found above 2700 m on north-facing slopes and above 3100 m on south-facing slopes. However, rock glacier activity has been detected with fronts as low as 2500 m above sea level, in environments with positive MAAT, indicating the presence of permafrost at lower elevations than expected. Here we present some of the preliminary results from the geophysical prospecting carried out in summer 2024 focusing on Magnetic Resonance Sounding (MRS) and Vertical electrical sounding (VES) in order to characterize subsurface frozen ground and water distribution in four rock glaciers: Ardiden (~2700), Besiberri (~2700 m), Broate (~2800 m) and Menera (~2500). Preliminary results indicate the existence of different layers of permafrost and/or buried ice with variable water content down to 25-45 m depth. While in one active rock glacier the frozen mass is continuous from ca. 3 to 45 m depth, the other three report two different layers at ca. 5-10 m, and below 20-25 m depth, which are associated with past morphogenic phases. These results will be also used to decide the sites for future permafrost boreholes that will be drilled in summer 2025 to monitor permafrost thermal state and assess its long-term evolution. The outcomes will contribute to global permafrost datasets and inform land management strategies in the Pyrenees.
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