Showing papers by "Wilfried Haeberli published in 1990"

Thermal characteristics of the permafrost within an active rock glacier (Murtèl/Corvatsch, Grisons, Swiss Alps)

Abstract: Temperatures from a bore hole through an active rock glacier in the eastern Swiss Alps are presented and thermal conditions within the slowly creeping permafrost are analyzed. Present mean annual temperature in the uppermost part of the permafrost is −3°C. Permafrost is 52 m thick and reaches heavily fissured bedrock. Thermal conductivity as determined in situ from seasonal temperature variations and measured in a cold laboratory using frozen samples is close to 2.5–3.0 W m−1 °C−1. Vertical heat flow is anomalously high (around 150 mW m-2), probably due to heat advection from circulating ground water or air within the fissured bedrock zone. Beneath this zone, which could in fact represent a non-frozen intra-permafrost layer or “talik”, relic permafrost from past centuries may possibly exist as indicated by a corresponding heat-flow inversion. Given the current temperature condition at the surface of the rock glacier and the fact that the twentieth century is among the warmest in post-glacial time, permafrost conditions may be assumed to have existed during the whole of the Holocene and, hence, during the entire time of rock-glacier formation.

Glacier and Permafrost Signals of 20th-Century Warming

Abstract: Currently-available evidence of 20th-century warming from glaciers and permafrost is briefly reviewed. The signals are clear and strong: warming of polar firn and permafrost, and mass losses of glaciers at lower latitudes, were most striking towards the middle of the century. The easily observable length-reduction of mountain glaciers confirms the global character of the evolution. A probably intermittent reversal of the trend was observed in places after about 1950.

Climatic change in a high- altitude alpine area suggested by the isotopic composition of cold basal glacier ice

Abstract: For the first time, a cold ice cover of a summit in the central Swiss Alps has been sampled from the surface to the bed for determining its isotopic composition in δD and δ18O. Results of the analyses show a striking decrease of δ-values with depth. The δ-value differences are greater than those explicable by a direct temperature effect, but a substantial increase in melt water percolation through the firn since the formation of the deepest ice layer may explain the situation of this high-altitude ice. -Authors