Cold scree slope
Elevation: 1520-1700m - Massif: Mont Blanc (Trient) - Commune: Orsières (VS)
This mid-altitude forested site was first mentioned in September 1981 when ice was discovered during construction works for one of the first pylons of the Breya chairlift. From 2004 onwards a few temperature loggers have been installed. The data showed that this cold zone is located in the lower section of a scree slope, which is subject to an internal ventilation mechanism. The internal air flow direction is reversible. It flows downwards while air temperatures remain above approximately +5 °C and upwards in the reverse case. As a result, lower sections stay constantly cold, thus providing conditions for the occurrence of permafrost.
Measurements and observations
Thermal (ground surface temperature : GST)
Daily sub-surface temperature of the talus slope. Cx-11 is located nearby the pylon of the chairlift, Cx-09 about 50 m eastwards in the coldest area of the talus slope.
Mean annual sub-surface temperature of the talus slope. Cx-11 is located nearby the pylon of the chairlift, Cx-09 about 50 m eastwards in the coldest area of the talus slope.
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)