A first estimate of permafrost distribution from BTS measurements in the Romanian Carpathians (Retezat Mountains)

A first estimate of permafrost distribution in the central part of the Retezat Mountains (Southern Carpathians, Romania) was computed using basal temperature measurements of winter snow cover as input data for an empirical-statistical modelling approach. During the 2012-2013 winter season, a total of 170 bottom temperature of snow cover measurements (Haeberli, 1973) were made. The permafrost distribution within the investigated area was modelled based on multiple linear regression analysis of the relationship between bottom temperature of snow cover measurements and five predictor variables: elevation, solar radiation, vegetation cover, slope and profile curvature. The final model, having an overall accuracy of 0.48, included only the first three variables as the main factors controlling permafrost occurrence within the investigated area, while slope and profile curvature proved to be statistically insignificant. Permafrost occurrence, as predicted by the model, covers 31 km2 (52% of the investigated area), of which 14 km2 is predicted as probable permafrost and the remaining 17 km2 is possible permafrost. The obtained results indicate the importance of solar radiation, elevation and vegetation cover in controlling alpine permafrost occurrence in the central part of the Retezat Mountains.Cet article fournit une première évaluation de la distribution du pergélisol dans la partie centrale du massif de Retezat (Carpates du Sud, Roumanie), utilisant des valeurs BTS (température à la base de la neige) comme indicateur de pergélisol dans un modèle statistique. Un total de 170 points BTS a été mesuré pendant la saison hivernale 2013-2014. La distribution du pergélisol est modélisée à l’aide d’une régression linéaire multiple entre les valeurs BTS et cinq variables indépendantes : l’altitude, la radiation solaire, la végétation, la pente et la courbure du profil. L’analyse statistique montre que la pente et la courbure du profil ne sont pas significatives. Par suite, les trois autres variables ont été incluses dans le modèle final, indiquant une précision de 0,48. Ce modèle montre que le pergélisol couvre une surface de 31 km2 (52% de la zone étudiée) dont 14 km2 représentent du pergélisol probable (PRP) et 17 km2 du pergélisol possible (PP).Les résultats mettent l’accent sur l’importance de la radiation solaire, l’altitude et la végétation dans l’occurrence du pergélisol, dans la partie centrale du massif de Retezat

Snow avalanche synchronicity derived from a multi-path tree-ring reconstruction in the Făgăraș Mountains (Southern Carpathians, Romania)

Snow avalanches pose a constant threat to human lives, property, and infrastructure in mountainous regions worldwide. To efficiently manage avalanche-related hazards and risks, knowledge of past occurrences is crucial. In many mountain regions, archival records on past events are scarce or even completely missing. Therefore, natural archives, such as tree-rings, are widely used as proxies to build century-long snow avalanche chronologies. However, most dendrogeomorphic studies focus on a small number of sites, providing only path-scale reconstructions with limited significance for a larger area. To overcome this problem, in the present study, we analyzed 17 avalanche paths in a small and relatively homogeneous region located in the F˘ag˘araș Mountains, Southern Carpathians, and documented past snow avalanche activity with dendrogeomorphic techniques. Increment cores extracted from 933 Picea abies trees allowed the reconstruction of a total of 174 snow avalanche years across all investigated paths. At the same time, widespread snow avalanche occurrence was identified in the study area. In years such as 1923, 1929, 1988, 1992, 1995, 1997, 2002, and 2005, more than half of the investigated paths experienced at least a major snow avalanche event. Regarding the frequency of event years, we conclude that the mean recurrence interval of widespread/extreme events is 4.1 years. Finally, this study highlights the importance of investigating multiple avalanche paths in a small, homogeneous area to create a better understanding of snow avalanche activity at path- and mountain range-scale. </p