Mountain permafrost in the Central Pyrenees: insights from the Devaux ice cave

[摘要] Ice caves are one of the least studied parts of the cryosphere, particularlythose located in inaccessible permafrost areas at high altitudes or highlatitudes. We characterize the climate dynamics and the geomorphologicalfeatures of Devaux cave, an outstanding ice cave in the Central Pyrenees onthe French–Spanish border. Two distinct cave sectors were identified basedon air temperature and geomorphological observations. The first onecomprises well-ventilated galleries with large temperature oscillationslikely influenced by a cave river. The second sector corresponds to moreisolated chambers, where air and rock temperatures stay below0  ∘ C throughout the year. Seasonal layered ice and hoarfrostoccupy the first sector, while transparent, massive perennial ice is presentin the isolated chambers. Cryogenic calcite and gypsum are mainly presentwithin the perennial ice. During winter, the cave river freezes at theoutlet, resulting in a damming and backflooding of the cave. We suggestthat relict ice formations record past damming events with the subsequentformation of congelation ice. δ 34 S values of gypsumindicate that the sulfate originated from the oxidation of pyrite present inthe bedrock. Several features including air and rock temperatures, theabsence of drips, the small loss of ice in the past 7 decades, and thelocation of ice bodies in the cave indicate that the cave permafrost is theresult of a combination of undercooling by ventilation and diffusive heattransfer from the surrounding permafrost, reaching a thickness of ∼  200 m.

[学科分类] 社会科学、人文和艺术（综合）