Lukas U. Arenson

Mountain permafrost: development and challenges of a young research field

An overview is given of the relatively short history, important issues and primary challenges of research on permafrost in cold mountain regions. The systematic application of diverse approaches and technologies contributes to a rapidly growing knowledge base about the existence, characteristics and evolution in time of perennially frozen ground at high altitudes and on steep slopes. These approaches and technologies include (1) drilling, borehole measurement, geophysical sounding, photogrammetry, laser altimetry, GPS/SAR surveying, and miniature temperature data logging in remote areas that are often difficult to access, (2) laboratory investigations (e.g. rheology and stability of ice– rock mixtures), (3) analyses of digital terrain information, (4) numerical simulations (e.g. subsurface thermal conditions under complex topography) and (5) spatial models (e.g. distribution of permafrost where surface and microclimatic conditions are highly variable spatially). A sound knowledge base and improved understanding of governing processes are urgently needed to deal effectively with the consequences of climate change on the evolution of mountain landscapes and, especially, of steep mountain slope hazards as the stabilizing permafrost warms and degrades. Interactions between glaciers and permafrost in cold mountain regions have so far received comparatively little attention and need more systematic investigation.

MULTIDISCIPLINARY INVESTIGATIONS ON THREE ROCK GLACIERS IN THE SWISS ALPS: LEGACIES AND FUTURE PERSPECTIVES

Abstract This paper recognizes the contribution of Professor Wilfried Haeberli for his inspiration and leadership in the field of permafrost science and his generous encouragement, both direct and indirect, to the ETH Researchers who have, through him, endeavoured to contribute to this fascinating research area. The multidisciplinary investigations described in this paper have focused on three rock glaciers, Muragl, Murtèl‐Corvatsch and Furggwanghorn, all of which have been subject to a varying degree of prior study, and which are continuing to attract new generations of researchers to understand and explain the processes and predict future behaviour. This paper marks a stage at which it is possible to summarize some advances in the state of the art and associated innovations that can be attributed to early motivation by Wilfried Haeberli and offers a tribute as well as gratitude for his ongoing feedback and advice. Some thoughts on the development of thermokarst due to water ponding and flow, and a conceptual model of geotechnical mechanisms that aim to explain some aspects of rock glacier kinematics, are also introduced.

The use of a convective heat flow model in road designs for Northern regions

Roads and highways in northern environments are exposed to harsh climatic conditions. In particular, changes in temperature of several tens of degrees centigrade between the seasons, and substantial precipitation as well as permafrost conditions are common. These environmental conditions result in significant damages to the infrastructure that requires extensive maintenance. Road damage is directly related to problems associated with the foundation, frequently resulting in differential settlements. Significant increase in these problems is expected as a result of changing climate, thus reducing the expected service life of various roads in arctic regions. The highway system within the permafrost region is extremely vulnerable to these climate changes because the mechanical property of the soil changes dramatically with temperature increases and as ice within the frozen soil thaws. This paper presents a numerical investigation of a novel approach for an improvement of road foundations resulting from convective heat flow. The proposed foundation is capable of compensating for some of the expected warming of the permafrost by storing and maintaining the cold winter temperatures through the summer months. The numerical model demonstrated the importance of considering convective heat flows to optimize the design of the foundation with a focus on minimizing the effect of climate warming.

Effects of Dust Deposition on Glacier Ablation and Runoff at the Pascua-Lama Mining Project, Chile and Argentina

Dust deposition on surficial ice bodies is common in many areas around the world. In the high and arid northern Chilean and Argentine Andes, the public fears the dust generated by mining activities would increase ice ablation and thus decrease downstream water availability. This fear is based on a poor understanding of the complex and non-linear interaction between dust and glacier ablation as well as the uncertainties about relative contribution of glacier containing watersheds to total runoff at the point of water use. The focus of this contribution is to assess impacts to down gradient water users resulting from increases in ablation due to dust. Depending on the thickness, type, frequency of deposition and concentration of the dust on the ice surface, a net increase or decrease in ice ablation may occur. While a thin dust cover reduces the surface albedo and hence increases ablation, a thicker cover increasingly acts as thermal insulation, thus reducing ice ablation and increasing the glacier’s longevity. Data from literature indicate that at less than 1 mm dust thickness ablation rates peak, resulting in ablation increases between 20 and 400 %. Field ablation tests and numerical dust distribution models for three different scenarios demonstrate that for the Andean site investigated, the downstream hydrological effects of mining-generated dust on glaciers and glacierets, at the first point of agricultural water use, are likely less than half a percent of the annual average river flow. This is largely due to the very small percent of glacial coverage upstream of the first water use point and is well below the local hydrological natural variability that is primarily driven by El Nino events.

Periglacial Geohazard Risks and Ground Temperature Increases

Climate change can impact glacial and periglacial environments, which are likely transforming at unprecedented rates during the Holocene. Progressive increases in air temperature and the associated modification in the ground thermal regime and surface energy balance result in increasing active layer thicknesses, ground warming, changing runoff and alterations in the freeze-thaw cycles. As a consequence to these thermal fluxes and their second order impacts to geomorphological processes the potential for slope instabilities changes accordingly. Active layer detachments, thermokarst or increased mass movement frequency due to frost weathering may result in hitherto unknown, or at least under-appreciated hazards because they may not have led to losses in the past. Where the hazard trajectory intercepts vulnerable infrastructure, geohazard risk may change in response. Quantitative geohazard risk assessments rely on frequency-magnitude relationships constructed from compilation and analyses of proxy data or direct observations. These analyses typically assume data stationarity (i.e., no long-term change in the mean and variance of the reconstructed time series), an assumption that is increasingly questioned considering the observed changes in the periglacial belt. This realization demands alternate approaches in risk assessment. In this paper, we present a general framework for assessing changes in geohazard activity within the periglacial environment heralded by changes in permafrost and ground ice conditions. The proposed framework starts with an examination of the effect of changes in air temperature on the ground thermal regime. Hazard probability and consequences are then assessed. By comparing the risk level under current conditions with the risk associated under a projected change in certain climatic parameters, the sensitivity of the slope stability or strength to climate change can be approximated. Despite considerable uncertainties associated with predictions of a third-order effect of climate change, the general approach outlined in this paper provides at least a tool to identify areas and slopes with high vulnerability to climate change and at best offers a systematic tool to evaluate climate change impacts in the periglacial zone.

Change in Ice Lens Formation for Saline and Non-Saline Devon Silt as a Function of Temperature and Pressure

During the freezing of a fine grained soil, ice lens formation changes the structure of the soil and results in frost heave. The formation of the ice lenses is very complex and dynamic. The results are presented from laboratory freezing tests on saturated Devon silt, a frost-susceptible soil. A variety of pore-water salinities, vertical pressures, and temperature gradients were used to investigate the different effects on the freezing process and the formation of the ice lenses. Using a novel experimental methodology, ice lens growth at the pore scale was observed. Fluorescein was dissolved in the pore water, which allowed to locate unfrozen water under UV light. In this manner it was possible to visually observe and measure the ice lens growth ahead of and behind the frozen fringe. It is visually shown that the thickness of the ice lenses, the distances between the ice lenses and the thickness of the frozen fringe change with changing temperature gradient, vertical pressure and salinity. In addition, the ice structure within the saline soils became more three dimensional and irregular compared to the non-saline samples, where the ice lenses develop over the entire cross section of the sample.