Christophe Lambiel

Bio: Christophe Lambiel is an academic researcher from University of Lausanne. The author has contributed to research in topics: Rock glacier & Permafrost. The author has an hindex of 25, co-authored 83 publications receiving 2261 citations.

Permafrost is warming at a global scale

Abstract: Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007–2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.

Overview of rock glacier kinematics research in the Swiss Alps

Abstract: . The acceleration of rock glacier surface velocities over the two last decades and the destabilization of several landforms show that permafrost creep conditions are changing in the Alps. This article summarizes and presents current understanding of creep behaviour of rock glaciers in the Swiss Alps and emphasises changes that have occurred over the last years and decades. The almost homogeneous interannual behaviour of rock glaciers despite different geometry and activity rates indicates a common dependence on external climatic factors (summer air temperature, seasonal snowcover development) which govern changes observed in rock glacier creep rate. The article highlights ongoing efforts to document interannual variations of rock glacier kinematics for the whole area of the Swiss Alps.

Assessing reliability of 2D resistivity imaging in mountain permafrost studies using the depth of investigation index method

Abstract: 2D electrical resistivity tomography has been applied within a mountain permafrost environment to assist in ice location. In the context of climate change, a warming process could partially thaw this permafrost and thereby increase the risk of slope instabilities. The extent and location of permafrost are therefore of considerable interest to civil engineers. The most challenging aspect of resistivity surveys on mountain permafrost concerns the surface layer, which mainly consists of large blocks with air voids.To overcome the very poor electrical contact, long steel stakes and sponges soaked in salt water are used as electrodes. Nevertheless, only a weak current can be injected. Another challenging aspect is the high resistivity contrast between frozen and unfrozen material, which makes inversion and interpretation difficult and problematic. In order to assess whether features at depth, indicated by the data, are real or are artefacts of the inversion process, a special inversion algorithm was applied to process depth of investigation (DOI) index maps. This method carries out two inversions of the same data set using different values of the reference resistivity. The two inversions give the same resistivity values in areas where the data contain information about the resistivity of the subsurface. On the other hand, the final result depends on the reference resistivity in areas where the data do not constrain the model. As can be deduced from field data from the Swiss Alps and the Jura Mountains, this methodology prevents over-interpretations or misinterpretations of inversion results in mountain permafrost studies. From the DOI calculations, it is evident that little reliable information on the bedrock under the massive ice can be obtained immediately and that the resistivity within the high resistivity zones cannot be determined accurately. The DOI map also helps to explain the occurrence of erratic and non-geological structures at depth and indicates to what depth an inverted resistivity profile can provide results.

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

Abstract: 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. To date, the chimney effect has been reported mainly for cold and sometimes perennially frozen scree slopes situated at low elevations, far below the regional limit of the discontinuous mountain permafrost. This article reports observations made recently in the western Swiss Alps in several accumulations of coarse sediments (talus slopes, relict or 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 ...

Observations and considerations on destabilizing active rock glaciers in the European Alps

Abstract: In many high mountain regions, warming of perennially frozen ground in both coarse debris and rock walls has a major influence on slope stability. In this context, indications of destabilizing active rock glaciers, such as high horizontal velocities (up to 4 ma-1), front advance rates of up to 4 ma-1, and development of crevasse-like cracks (up to 14 m deep), have been documented and monitored in the Alps for a few years. Beside the limited knowledge of rock glacier dynamics, our principle hypothesis is that the primary factors controlling the development of cracks and the destabilization of rock glacier tongues are the rheological properties of warming ice. In addition, we postulate that hydrological effects of unfrozen water within the active layer, the permafrost body, or at its base may contribute to the initiation of the slide-like mass wasting.

Logistic Regression A Self Learning Text

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