Cold scree slopes
Elevation: 1630-1780m - Massif: Prealps of Fribourg - Commune: Haut-Intyamon (FR)
This mid-altitude site has been the object of thermal and geophysical measurements since 2001 in order to prove the existence of a ventilation mechanism inside the scree slope. The various measurements confirmed the existence of strong thermal differences, which are linked to the intra-scree ventilation mechanism, partly connected to the underlying karstic network. This internal scree air current is reversible. It flows in a descending direction while air temperatures remain above 4.5 °C. In the opposite case the air flow is ascending. Subsequently, lower sections of the scree slope stay constantly cold and the snow stays for a longer period. In the reverse case, no ice can be found in the upper sections of the scree slope and the snow-cover disappears quite rapidly.
Measurements and observations
Thermal (ground surface temperature: GST, BTS)
Year-round behavior of the ground surface temperature (daily mean, GST) on the talus slope #2. Vud-01 is located at the bottom of the talus slope, whereas Vud-04 is situated in the upper part. When a snow cover is present, the winter ground temperature stays significantly above 0°C (diffusion of warm air coming from the talus or the subjacent karstic system at the base of the snowpack) at Vud-04, whereas it remains strongly negative (aspiration of cold air though the snowpack) at Vud-01. In summertime Vud-01 is constantly (much) colder than Vud-04 due to the discharge of cold air from the interior of the talus slope (consecutive to the deep winter cooling / freezing).
Morard, S., (2011). Effets de la circulation d'air par effet de cheminée dans l'évolution du régime thermique des éboulis froids de basse et moyenne altitude. PhD thesis, Fac. Sciences, Univ. Fribourg, GeoFocus 29. (pdf)
Morard S., Delaloye R., Lambiel C., (2010). Pluriannual thermal behavior of low elevation cold talus slopes (western Switzerland). Geographica Helvetica, 65/2, 124-134. (pdf)
Morard S., Delaloye R., Dorthe, J. (2008). Seasonal thermal regime of a mid-latitude ventilated debris accumulation.Proceedings of the Ninth International Conference on Permafrost, July 2008, Fairbanks, Alaska, 1233-1238. (pdf)
Delaloye, R. (2004). Contribution à l’étude du pergélisol de montagne en zone marginale. PhD thesis, Fac. Sciences, Univ. Fribourg, GeoFocus 10 (pdf)