Rune Strand Ødegård

Mountain permafrost distribution in Dovrefjell and Jotunheimen, southern Norway, based on BTS and DC resistivity tomography data

The influence of climate and topography on the distribution of permafrost within the Dovrefjell and Jotunheimen areas, southern Norway, is analysed. A dataset of 972 BTS (bottom temperature of winter snow) measurements was analysed in relation to altitude, potential direct incoming radiation, aspect, snow depth, curvature and slope. To confirm and characterise permafrost-transition zones indicated from the BTS measurements, miniature temperature data-loggers, borehole temperatures, one-dimensional DC resistivity soundings and two-dimensional DC resistivity tomography were used. In addition, small-scale variance analyses upon the BTS values were performed using spatial-statistical methods. Results confirm that BTS values are highly correlated with altitude. Based on analysis of BTS data, the lower limit of possible permafrost is 1490 m a.s.l. on Dovrefjell and 1460 m a.s.l. in Jotunheimen. The relation between altitude and BTS suggests that the climate conditions on Dovrefjell and in Jotunheimen are similar with respect to permafrost distribution. Potential direct incoming radiation (PR) has a minor influence on BTS. A significant correlation between both surface moisture and surface type conditions in summer and BTS measurements were found. The results from Jotunheimen suggest that 20-45% of the variance in BTS results that are not explained by altitude are explained by small-scale spatial variance within a 20-30 m range. The results from the BTS measurements and the two-dimensional DC resistivity tomography were highly consistent.

Mapping and modelling the occurrence and distribution of mountain permafrost

This paper reviews the principles related to the mapping and modelling of the occurrence and distribution of mountain permafrost. It gives a state-of-the art report about this topic and defines future research needs.

Glacier characteristics and sediment transfer system of Longyearbreen and Larsbreen, western Spitsbergen

Two small high-Arctic glaciers (Longyearbreen and Larsbreen) on Svalbard (78°N 15°E) were studied with respect to glaciological and hydrological characteristics. Fieldwork during the melting season of 1993 and 1994 was coupled with digital map analysis based on high-resolution digital elevation models (DEM) to reveal the dynamics and temperature regime of small glaciers in a high-Arctic environment, and its relationship to the material transport and sedimentation of these glaciers. The study showed Longyearbreen and Larsbreen to be low activity glaciers, cold-based with temperate patches, and thus having a low potential of basal erosion. The transport of ions and suspended solids in the glacial meltwater implies storage of material in and around the glacier which comes into contact with the meltwater. The study suggests that small Arctic glaciers couple the slope system with the fluvial system and therefore build a highly effective denudation system. Small polythermal glaciers are therefore important in understanding Pleistocene and Holocene landform development in cold regions.

Comparison of BTS and Landsat TM data from Jotunheimen, southern Norway

Results from snow temperature measurements at the bottom of the winter snow cover (BTS) are compared with Landsat TM data in a preliminary analysis of the potential of using Landsat data in permafrost mapping in the area of Jotunheimen, southern Norway. Uncorrected apparent satellite temperatures (AST) from the thermal band were used to identify areas of high amplitude ground surface temperatures on the day of the satellite pass (15 August 1997) and the normalized difference vegetation index (NDVI) was applied to detect vegetation density. The BTS data are highly correlated with altitude. The analysis shows that AST makes a small, but significant, contribution towards explaining the variance of BTS at similar altitudes in a linear regression model. Use of the thermal data in the model seemed to remove the aspect dependency in the BTS data. Analysis of the residuals in a linear model including altitude and AST suggests that any improvement of the model must be based on parameters that vary systematically o...

The climatic significance of artefacts related to prehistoric reindeer hunting exposed at melting ice patches in southern Norway

The main aim of this study is to describe consequences of climate change in the mountain region of southern Norway with respect to recently exposed finds of archaeological remains associated with reindeer hunting and trapping at and around ice patches in central southern Norway. In the early years of the twenty-first century, warm summers caused negative glacier mass balance and significant glacier retreat and melting of ice patches in central southern Norway. As a result, prehistoric remains lost and/or left by past reindeer hunters appeared at ice patches in mountain areas of southern Norway. In the warm summer and autumn of 2006 the number of artefact recoveries at ice patches increased significantly because of melting of snow and ice patches and more than 100 objects were recovered in the Oppland county alone. In 2009, detailed multidisciplinary investigations were carried out at the Juvfonne ice patch in Jotunheimen at an elevation of c. 1850 metres. A well-preserved Iron Age hunting station was discovered and in total c. 600 artefacts have been documented at the Juvfonne site alone. Most of the objects were recovered and brought to the Museum of Cultural History at the University of Oslo for conservation, exhibition and storing. Thirteen so called ‘scaring sticks’ recovered from the recently exposed foreland of Juvfonne were radiocarbon dated, yielding ages that group in two separate time intervals, ad 246–534 and ad 804–898 (±1 sigma). By putting the temporal distribution of the radiocarbon-dated artefacts into the context of late-Holocene glacier-size variations in the Jotunheimen and Jostedalsbreen regions, we conclude that the most extensive reindeer hunting and trapping associated with snow/ice patches was related to periods with prevailing warm summers when the reindeer herds gathered on high-altitude, contracted glaciers and ice patches to avoid insect plagues. The ‘freshness’ of the fragile organic finds strongly indicates that at least some of the artefacts were rapidly covered by snow and ice and that they may have been more-or-less continuously covered by snow and ice since they were first buried.

Measuring coastal cliff retreat in the Kongsfjorden area, Svalbard, using terrestrial photogrammetry

As part of the international project Arctic Coastal Dynamics, results from two sites for measuring coastal cliff retreat in the Kongsfjorden area in Svalbard (79 ° N, 13 ° E) are presented. The two sites were established in August 2002 and revisited in August 2004. Photographs with stereo coverage were taken at distances of 7 and 15 m from the cliff walls with a 60-mm Hasselblad camera mounted on a theodolite. Fixed points were established by drilling bolts into the cliff wall and were then surveyed. These fixed points were used as control points for orientation of the photogrammetric models. Digital photogrammetry applied to scanned photographs of the sites resulted in a detailed digital terrain model (DTM) for each site and year. The coastal cliff retreat rates were found by differencing the DTMs of 2002 and 2004. As a result of the short distance between camera and cliff, the DTM differencing was accurate down to 10 mm at least. The results show a yearly retreat of 2.7 and 3.1 mm. These rates are taken to be significant as most of the retreat takes place within small areas with rates well above the accuracy limits of the technique. The results are analysed and discussed in light of earlier rock-wall retreat studies in the same area.

Meltwater routing in a high arctic glacier, Hannabreen, northern Spitsbergen

Electrical conductivity and chemistry of meltwaters draining glaciers have been used to study spatial differences and seasonal variations in melwater routing (e.g. Collins 1977, 1979 Tranter et al. 1993, Hodgkins et al. 1995). Collins (1977,1979) suggested a model to separate bulk runoff into a rapid englacial flow component and a delayd subglacial flow component. The model is based on the higher electrical conductivity of the subglacial component than the englacial component, assuming the conductivity of each component to be relatively constant throughout the ablation season. Tranter et al. (1993) argues that althrough such a model describes many features of the subglacial drainage system, it is unlikely that the chemical composition of each component is constant over the ablation season. The anionic composition of meltwater seems to provide a diagnostic basis for determining the flow routing of meltwater. SO4 2- is particularly useful, because sulphide oxidation is a rapid reaction which commonly goes t...

Glacier radar sounding using multiple-frequency bands

A glacier consists of physical structures covering a large span of length scales. The different scales can be mapped using different radar frequencies. The bottom topography is mapped using HF frequencies (5 - 20 MHz). The internal structure is seen at UHF frequencies (100 - 500 MHz). The snow cover and firn layers can be mapped with frequencies around 1 GHz.

Technological concepts for modelling, monitoring and mapping the terrestrial cryosphere on continental to global scale

This paper focuses on modelling, monitoring and mapping concepts on a continental to global scale, using geo-referenced data from the terrestrial cryosphere as an example. The discussion takes a technological approach, showing how geographical information technology (GIT) and computer science can be used by scientists to improve the analysing capabilities of Earth observations from these often remote polar and mountainous areas. Huge amounts of geo-referenced measurements with relevance to the terrestrial cryosphere are presently available to the scientific community and the general public. This is a mixture of in situ and remote-sensing measurements, derived products and model results. The amount of data will probably increase exponentially in the future, particularly remote-sensing data. Making global analysis, including all available cryospheric variables, will require a common technological platform with the required data structures and analysing capabilities. A system of networked databases is one solution to the problem. The technology is available, but implementation of such a system will require a greater emphasis on GIT and data integration in the design of observation and analysis systems for the terrestrial cryosphere. Such an integrated approach will probably increase the capabilities of detecting climatic change, e.g. by applying advanced time-space statistical analysis. Results of climate models could also be integrated on a common platform along with geospatial measurements and different derived products.