Christof Kneisel

Applied geophysics in periglacial environments

Part I. Introduction Part II. Introductory Chapters for the Main Geophysical Methods Applied: 1. Electric methods Christof Kneisel and Christian Hauck 2. Electromagnetic methods Andreas Hordt and Christian Hauck 3. Refraction seismics Lothar Schrott and Thomas Hoffmann 4. Ground-penetrating radar Ivar Berthling and Kjetil Melvold Part III. Case Studies: 5. Typology of vertical electrical soundings for permafrost/ground ice investigation in the forefields of small alpine glaciers Reynald Delaloye and Christophe Lambiel 6. ERT imaging for frozen ground detection Mamoru Ishikawa 7. Electrical resistivity values of frozen soil from VES and TEM field observations and laboratory experiments Koichiro Harada 8. Results of geophysical surveys on Kasprowy Wierch, the Tatra Mountains Wojciech Dobinski, Bogdon Zogala, Krystian Wzietek and Leszek Litwin 9. Reassessment of DC resistivity in rock glaciers by comparing with P-wave velocity: a case study in the Swiss Alps Atsushi Ikeda 10. Quantifying the ice content in low-altitude scree slopes using geophysical methods Christian Hauck and Christof Kneisel 11. The use of GPR in determining talus thickness and talus structure Oliver Sass 12. GPR soundings of rock glaciers on Svalbard Ivar Berthling, Bernd Etzelmuller, Herman Farbrot, Ketil Isaksen, Morgan Wale and Rune Odegard 13. Arctic glaciers and ground-penetrating radar case-study: Stagnation Glacier, Bylot Island, Canada Tristram D. L. Irvine-Fynn and Brian J. Moorman 14. Mapping of subglacial topography using GPR for determining subglacial hydraulic conditions Kjetil Melvold and Thomas V. Schuler 15. Snow measurements using GPR: example from Amundsenisen, Svalbard Kjetil Melvold 16. Mapping Frazil ice conditions in rivers using ground penetrating radar Ivar Berthling, Halfdan Benjaminsen and Anund Kvambekk Part IV. Tables of Typical Values of Geophysical Parameters for Periglacial Environments Index.

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.

Melting Glaciers and Soil Development in the Proglacial Area Morteratsch (Swiss Alps): I. Soil Type Chronosequence

ABSTRACT Proglacial areas in the Alps usually cover a time span of deglaciation of about 150 years (time since the end of the “Little Ice Age” in the 1850s). In these proglacial areas soils have started to develop. In view of the foreseeable climate change, the time factor is of growing interest with respect to the landscape and consequently the soil development. We investigated soil changes (primarily on the basis of soil types) in the proglacial area Morteratsch (Swiss Alps) to derive time trends that can be used as a basis for spatial modeling. Differences in the soil development could be primarily interpreted in view of the time scale and topography (landscape shape, slope, aspect). Data was managed with GIS and regression analyses. Input data sets were the digital soil map, the glacial states, and the digital elevation model. The calculations were done raster based (GRID, 20 m resolution). After about 20 years the first signs of soil development could be found. Around 25% of the area of the valley floor is covered with weakly developed Skeletic/Lithic Leptosol after about 30 years of deglaciation. One hundred years of soil development led to a strong decrease of the Skeletic/Lithic Leptosol in favor of the Humi-Skeletic Leptosol and Ranker. Fluvisols and Cambisols play a subordinate role also after 100–150 years. Undisturbed and fast soil evolution was measured in flat positions and on slopes up to about 14°. In general, the various landforms also correlated well with soil evolution. One of the most surprising facts was that the weathering between south- and north-facing sites differed distinctly, with the north-facing sites having the higher weathering rates. Soil moisture seems to be a decisive factor in weathering. Thicker snow packs probably inhibit or reduce soil frost and allow larger fluxes of snowmelt water to infiltrate into already moist profiles. Slope, exposure and to a lesser extent also the landform determined the soil development: these influences could be quantified using regression analyses. These analyses serve as a basis for further spatio-temporal modeling.

Sediment Budget and Relief Development in Hrafndalur, Subarctic Oceanic Eastern Iceland

Abstract There have been only a few truly integrated quantitative studies on sediment budgets and relief development in cold environments. For a combined quantitative investigation of the relevant denudative slope processes and stream work in the 7 km2 catchment Hrafndalur, situated in a rhyolite area in the northern part of the Icelandic Eastern Fjords region (Austfirðir), information was collected on the absolute and relative importance of the different denudative processes. Integration of the six-year monitoring program with the analysis of Holocene storage elements using geophysical techniques allows estimates on Holocene process intensities in addition to the measured present-day sedimentary transfers. With respect to mass transfers, fluvial suspended sediment plus bed-load transport is most relevant and is followed by fluvial solute transport, rock and boulder falls, chemical slope denudation, mechanical fluvial slope denudation (slope wash), creep processes, avalanches, debris flows, translational slides, and deflation. Due to comparably high mechanical weathering and sedimentary transfer rates, postglacial modification of the Pleistocene glacially formed landscape is clearly more advanced than in the extended basalt areas of Austfirðir. Postglacial relief development is characterized by a valley widening due to the active retreat of rock walls and the formation of extended talus cones coupled with channel systems.

Melting Glaciers and Soil Development in the Proglacial Area Morteratsch (Swiss Alps): II. Modeling the Present and Future Soil State

ABSTRACT Climate change due to anthropogenic emissions of greenhouse gases is predicted to increase the average surface temperature. The most evident soil changes in the Alps will occur in proglacial areas where already existing young soils (with an age in most cases of up to 150 years) will continuously develop and new soils will form due to glacier retreat. Based on existing soil chronosequence data and statistical analyses in the proglacial area Morteratsch (Switzerland), the present-day state of the soils as well as their future development in the next 100 years in the existing and new proglacial area has been modeled taking the retreat of the glacier into consideration. The present-day as well as the future soil distribution was modeled using a probabilistic approach. Several soil characteristics have been modeled such as the pH value, the skeleton content, and the soil depth relevant to plant growth. To model soil properties in a future proglacial area (that is now covered by ice), the glacier-bed morphology had to be modeled. The calculations were performed using the cubic Non-Uniform Rational B-Spline (NURBS) curve to parameterize the course of a branch in flow direction. With the help of the ice cap and relief factor the thickness of the glacier was modeled. Climate change was introduced numerically by changing the mass balance of the glacier. For the area of interest a temperature increase of +1.6°C by the year 2050 and +3°C by the year 2100 can be assumed (according to the scenario A1B of IPCC). In the upper part of the proglacial area mostly Skeletic/Lithic Leptosols and Humi-Skeletic Leptosols will be found. In flat parts close to the main river, additional Fluvisols will develop. A considerable part of the upper proglacial area does not have any soil cover. Lithic/Skeletic to Humi-Skeletic Leptosols are modeled on the young lateral moraines. Chronosequences were vital to make any (4D) predictions of soil evolution in the proglacial area. The statistically and probabilistically based model also had, however, its weaknesses. The problems are related to the sediment properties in the glacier bed and the stability of new moraines.

The nature and dynamics of frozen ground in alpine and subarctic periglacial environments

A spatial assessment of the complex discontinuous and sporadic permafrost distribution and characteristics in high-altitude alpine and high-latitude subarctic permafrost environments was achieved using a combination of different methodological approaches consisting of traditional (geomorphological mapping) and modern techniques (2D near surface geophysics, surface and subsurface temperature monitoring). For the study of alpine and subarctic mountain permafrost with small-scale heterogeneity of surface and subsurface characteristics electrical resistivity tomography (ERT) has proven to be an especially well-suited and multifunctional method. Synoptic comparison of the nature and dynamics of frozen ground in alpine and subarctic periglacial environments confirmed heterogeneous and patchy permafrost occurrences showing a strong relationship to the surface textural characteristics and snow cover distribution and duration. Concerning frozen ground dynamics there is geomorphological and geophysical evidence for permafrost aggradation and degradation. At present both processes are possible in the investigated study areas with small-scale variation of the environmental factors. It can be concluded that permafrost with a timescale varying from several decades to a few thousand years can coexist in close proximity, such as, for instance, subrecent permafrost formation in a recently exposed glacier forefield and Holocene push moraines and rock glaciers. In order to account for the small-scale heterogeneity geomorphological field observations, geophysical mapping and multiple in situ measurements are required to understand complex periglacial environments, to monitor the contemporary permafrost conditions and enable a differentiation between interannual fluctuations from long-term trends. Such integrated approaches are thought to have the potential to improve the understanding of the Holocene and subrecent landscape evolution in complex glacial and periglacial environments which may exhibit active, inactive and relict landforms in close proximity.

Comparison of spatial modelling and field evidence of glacier/permafrost relations in an Alpine permafrost environment

Abstract According to geographic information system-based modelling, the Muragl glacier forefield situated in the St Moritz area, eastern Swiss Alps, lies in a potential permafrost area. As an attempt to verify spatial modelling, BTS (bottom temperature of the winter snow cover) measurements, geoelectrical soundings and geomorphological mapping were carried out in order to investigate the present-day permafrost and ground-ice distribution in this forefield. Recent geomorphodynamic processes in the steep upper slopes of the cirque include small debris flows and several slides related to the occurrence of ground ice. The occurrence of fluted moraines and a well-developed push moraine provides geomorphological evidence for a complex thermal regime of the former Muragl glacier, with cold marginal parts frozen to the bed, and warm-based ice in more central parts where fluted moraines could develop. Details of the inferred glacier/permafrost interaction are difficult to interpret. The results of field measurements (BTS and geoelectrical soundings) in the recently deglaciated forefield indicate the local occurrence of permafrost in the forefield and in the push moraine. In most parts of the forefield, permafrost may be assumed to be a former subglacial occurrence. However, new permafrost formation in the recently deglaciated forefield cannot be excluded.

Reconnaissance surveys of contemporary permafrost environments in central iceland using geoelectrical methods: implications for permafrost degradation and sediment fluxes

Abstract. Four different sites in the highlands of central Iceland have been investigated for permafrost occurrence using two‐dimensional resistivity imaging. The results of the surveys indicate the presence of shallow permafrost of low to medium resistivity. The distribution pattern is spatially heterogeneous which is consistent with permafrost at the fringe of seasonal frost. These sites are likely to react rapidly to changes of the environmental boundary conditions, therefore future research should include monitoring for detecting the early impact of climate change on permafrost degradation. The extent to which periglacial morphodynamics and sediment fluxes are influenced by permafrost and/or seasonal frost and potential permafrost degradation is hard to determine. Hence, long‐term monitoring approaches for both permafrost and sediment dynamics are essential.

Soil formation and weathering in a permafrost environment of the Swiss Alps: A multi-parameter and non-steady-state approach

Spatially discontinuous permafrost conditions frequently occur in the European Alps. How soils under such conditions have evolved and how they may react to climate warming is largely unknown. This study focuses on the comparison of nearby soils that are characterised by the presence or absence of permafrost (active-layer thickness: 2 – 3 m) in the alpine (tundra) and subalpine (forest) range of the Eastern Swiss Alps using a multi-method (geochemical and mineralogical) approach. Moreover, a new non-steady-state concept was applied to determine rates of chemical weathering, soil erosion, soil formation, soil denudation, and soil production. Long-term chemical weathering rates, soil formation and erosion rates were assessed by using immobile elements, fine-earth stocks and meteoric 10Be. In addition, the weathering index (K + Ca)/Ti, the amount of Fe- and Al-oxyhydroxides and clay minerals characteristics were considered. All methods indicated that the differences between permafrost-affected and non-permafrost-affected soils were small. Furthermore, the soils did not uniformly differ in their weathering behaviour. A tendency towards less intense weathering in soils that were affected by permafrost was noted: at most sites, weathering rates, the proportion of oxyhydroxides and the weathering stage of clay minerals were lower in permafrost soils. In part, erosion rates were higher at the permafrost sites and accounted for 79 – 97% of the denudation rates. In general, soil formation rates (8.8 – 86.7 t/km2/y) were in the expected range for Alpine soils. Independent of permafrost conditions, it seems that the local microenvironment (particularly vegetation and subsequently soil organic matter) has strongly influenced denudation rates. As the climate has varied since the beginning of soil evolution, the conditions for soil formation and weathering were not stable over time. Soil evolution in high Alpine settings is complex owing to, among others, spatio-temporal variations of permafrost conditions and thus climate. This makes predictions of future behaviour very difficult. This article is protected by copyright. All rights reserved.