Faculté des sciences

Evidences of winter ascending air circulation throughout talus slopes and rock glaciers situated in the lower belt of alpine discontinuous permafrost (Swiss Alps)

Delaloye, Reynald ; Lambiel, Christophe

In: Norwegian Journal of Geography

The winter ascending circulation of air throughout an accumulation of coarse slope sediments (the so-called chimney effect) facilitates the cooling of the ground and even the occurrence of permafrost in the lower part of a deposit. Simultaneously, any freezing is unlikely to occur in the upper part. The chimney effect has been reported to date mainly for cold and sometimes perennially frozen... Plus

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    Summary
    The winter ascending circulation of air throughout an accumulation of coarse slope sediments (the so-called chimney effect) facilitates the cooling of the ground and even the occurrence of permafrost in the lower part of a deposit. Simultaneously, any freezing is unlikely to occur in the upper part. The chimney effect has been reported to date mainly for cold and sometimes perennially frozen scree slopes situated at low elevations, far below the regional limit of the discontinuous mountain permafrost. This paper reports observations performed recently in the western Swiss Alps in several accumulations of coarse sediments (talus slopes, relict/inactive rock glaciers) located at higher elevations (2200-2800 m a.s.l.) within the belt of discontinuous permafrost or close to its lower limit. These observations show that a chimney effect may also occur in debris accumulations situated at ‘usual’ mountain permafrost elevation. This gives rise to multiple questions, in particular about the impact of the chimney effect on both the thermal regime and the spatial distribution of discontinuous mountain permafrost.