Near–surface ground temperature regime variability in selected microenvironments, Kärkevagge, Swedish Lapland

The importance of topographic microvariability in influencing shallow (10–50 cm depths) soil temperature regimes in arctic–alpine Kärkevagge, northern Sweden, from August 1999 to July 2000 is demonstrated using six sites. The ground microclimate on the tops of very large boulders forming an extensive boulder field in the central valley bottom is more comparable to that at an alpine ridge–crest site 300 m higher than it is to the microclimate at the base of one of the boulders. The boulder crests also differ substantially from the more generalized valley–bottom conditions outside the boulder field. Assuming that chemical processes may be active at temperatures at or above 0°C, sites in the valley experience favorable conditions from 159 to 324 days of the year. Aside from the annual cycle, freeze–thaw cycles are infrequent within Kärkevagge.     

Near–surface ground temperature regime variability in selected microenvironments, Kärkevagge, Swedish Lapland

The importance of topographic microvariability in influencing shallow (10–50 cm depths) soil temperature regimes in arctic–alpine Kärkevagge, northern Sweden, from August 1999 to July 2000 is demonstrated using six sites. The ground microclimate on the tops of very large boulders forming an extensive boulder field in the central valley bottom is more comparable to that at an alpine ridge–crest site 300 m higher than it is to the microclimate at the base of one of the boulders. The boulder crests also differ substantially from the more generalized valley–bottom conditions outside the boulder field. Assuming that chemical processes may be active at temperatures at or above 0°C, sites in the valley experience favorable conditions from 159 to 324 days of the year. Aside from the annual cycle, freeze–thaw cycles are infrequent within Kärkevagge.     

Enigmatic Efflorescence in Kärkevagge, Swedish Lapland: The Key to Chemical Weathering?

The second marvel to catch the eye of the visitor to Kärkevagge, after the impressive boulder deposit on the floor of the valley, is the series of prominent white stripes running down the valley's dark cliffs. Streams and springs descending the eastern flank of Kärkevagge are marked by the presence of whitish coatings on the black rock surfaces and on cobbles lining ephemeral waterways. These were referred to as 'lime crusts' by early investigators, but they are not reactive to HCl. We believe that they are a precipitate resulting from acid attack on the local rocks. Pyrite is common in many of the rocks in the valley and its oxidation produces sulfuric acid. As the dissolved mineral elements are carried in the drainage water, efflorescence forms on the surfaces where the water flows due to evaporation or to changes in temperature. The exact mineralogy of the white crusts is unknown, but the crusts are dominated by Al, S, and O, and in some cases by Ca, depending on the substrate and local conditions. Gypsum, illite, and chlorite have been identified by X–ray diffraction of some scrapings of white–coated rocks. However, we believe that some unidentified oxy–hydroxy aluminum sulfates make up the bulk of the precipitates.     

Chemical denudation rates in Kärkevagge, Swedish Lapland

This study examines the spatial and temporal variability of chemical denudation rates in Kärkevagge, northern Sweden. The chemical flux rates within the valley are strongly influenced by the local geology. Chemical denudation rates determined for the study period are more than double those previously reported in the literature for this valley. Rates of greater than 46t km⁻² a⁻¹ were measured at the valley mouth over the course of the melt season. This difference is likely due to differences in measurement technique compared to that used by past researchers. This rate is also much higher than for other arctic and alpine watersheds. Chemical denudation in Kärkevagge is comparable to larger temperate rivers. The rapid chemical denudation in Kärkevagge is likely due to sulfide weathering creating acid solutions.     

Chemical denudation rates in Kärkevagge, Swedish Lapland

This study examines the spatial and temporal variability of chemical denudation rates in Kärkevagge, northern Sweden. The chemical flux rates within the valley are strongly influenced by the local geology. Chemical denudation rates determined for the study period are more than double those previously reported in the literature for this valley. Rates of greater than 46t km⁻² a⁻¹ were measured at the valley mouth over the course of the melt season. This difference is likely due to differences in measurement technique compared to that used by past researchers. This rate is also much higher than for other arctic and alpine watersheds. Chemical denudation in Kärkevagge is comparable to larger temperate rivers. The rapid chemical denudation in Kärkevagge is likely due to sulfide weathering creating acid solutions.     

Enigmatic Efflorescence in Kärkevagge, Swedish Lapland: The Key to Chemical Weathering?

The second marvel to catch the eye of the visitor to Kärkevagge, after the impressive boulder deposit on the floor of the valley, is the series of prominent white stripes running down the valley's dark cliffs. Streams and springs descending the eastern flank of Kärkevagge are marked by the presence of whitish coatings on the black rock surfaces and on cobbles lining ephemeral waterways. These were referred to as 'lime crusts' by early investigators, but they are not reactive to HCl. We believe that they are a precipitate resulting from acid attack on the local rocks. Pyrite is common in many of the rocks in the valley and its oxidation produces sulfuric acid. As the dissolved mineral elements are carried in the drainage water, efflorescence forms on the surfaces where the water flows due to evaporation or to changes in temperature. The exact mineralogy of the white crusts is unknown, but the crusts are dominated by Al, S, and O, and in some cases by Ca, depending on the substrate and local conditions. Gypsum, illite, and chlorite have been identified by X–ray diffraction of some scrapings of white–coated rocks. However, we believe that some unidentified oxy–hydroxy aluminum sulfates make up the bulk of the precipitates.     

天山南麓台兰河口丘状堆积物成因及时代的新见解

研究表明台兰河口的丘状堆积体属古泥石流成因，物质组成显示泥石流形成于中低山带的峡谷段，泥石流可能由谷坡堆积物（主要为钙质胶结的冰碛）滑塌阻塞河床发展而成。其形成时代晚于末次冰期，应在全新世中期或更晚一些。     

QUANTIFYING SEDIMENT TRANSPORT PROCESSES IN PERIGLACIAL MOUNTAIN ENVIRONMENTS AT A CATCHMENT SCALE USING GEOMORPHIC PROCESS UNITS

The research record on the quantification of sediment transport processes in periglacial mountain environments in Scandinavia dates back to the 1950s. A wide range of measurements is available, especially from the Kärkevagge region of northern Sweden. Within this paper satellite image analysis and tools provided by geographic information systems (GIS) are exploited in order to extend and improve this research and to complement geophysical methods. The processes of interest include mass movements such as solifluction, slope wash, dirty avalanches and rock- and boulder falls. Geomorphic process units have been derived in order to allow quantification via GIS techniques at a catchment scale. Mass movement rates based on existing field measurements are employed in the budget calculations. In the Kärkevagge catchment, 80% of the area can be identified either as a source area for sediments or as a zone where sediments are deposited. The overall budget for the slopes beneath the rockwalls in the Kärkevagge is approximately 680 t a⁻¹ whilst about 150 t a⁻¹ are transported into the fluvial system.     

STORURDI: A LATE HOLOCENE ROCK-SLOPE FAILURE (STURZSTROM) IN THE JOTUNHEIMEN, SOUTHERN NORWAY

An extensive accumulation of rock debris at the mouth of Urdadalen in the Jotunheimen, southern Norway, is interpreted as the deposit of a rock-slope failure (sturzstrom). This is the first large-scale rock-slope failure to be recognised in the Jotunheimen but is unlikely to be the only one. The debris descended to the valley floor, passed across the valley axis and moved 40 m up the opposite side of the valley. Some debris passed over the lip of Urdadalen and now forms a boulder tongue that extends for c. 800 m into Utledalen. A maximum velocity of 80 m s⁻¹ for debris movement from crest of hillside to toe of boulder tongue has been estimated, and a minimum velocity of 28 m s⁻¹ was required for the debris to run up the opposite side of Urdadalen. The degree of boulder hardness/weathering as determined by Schmidt hammer suggests the sturzstrom occurred in the Late Holocene (1.825 ± 0.76 cal. ka bp ), during a period of climatic deterioration. The localised geomorphological impact of the failure event has been to dam the valley and create a small lake, to cause valley widening, to produce a north-facing hillside embayment at 1200–1400 m above sea level with the potential to collect and retain snow that might, in future, lead to niche glacier development and cirque initiation, and to provide a large volume of rock debris for entrainment and onward transport in future glacial cycles.     

Gelifluction within a solifluction lobe in the Kärkevagge valley, Swedish Lapland

Soil displacement, soil temperature, depths of thaw plane and groundwater level were continuously monitored during the period from July 1999 to June 2000 within a solifluction lobe in the Kärkevagge valley, northern Sweden. The strain–probe method was used to measure soil displacement, and we found significant soil displacements in the thawing period 2000. These displacements were the result of gelifluction. The ice content profile showed that gelifluction occurred at the same time as the thaw plane reached the layers with high ice content at shallow soil depths (0–6 and 16–25 cm deep). In contrast, gelifluction did not occur when the thaw plane reached the layers with high ice content at greater depth (46–49 cm deep). These observations indicate that thawing of ice lenses in the near–surface layer triggers gelifluction.     

Gelifluction within a solifluction lobe in the Kärkevagge valley, Swedish Lapland

Soil displacement, soil temperature, depths of thaw plane and groundwater level were continuously monitored during the period from July 1999 to June 2000 within a solifluction lobe in the Kärkevagge valley, northern Sweden. The strain–probe method was used to measure soil displacement, and we found significant soil displacements in the thawing period 2000. These displacements were the result of gelifluction. The ice content profile showed that gelifluction occurred at the same time as the thaw plane reached the layers with high ice content at shallow soil depths (0–6 and 16–25 cm deep). In contrast, gelifluction did not occur when the thaw plane reached the layers with high ice content at greater depth (46–49 cm deep). These observations indicate that thawing of ice lenses in the near–surface layer triggers gelifluction.     

Identification of geomorphic process units in Kärkevagge, northern Sweden, by remote sensing and digital terrain analysis

Sediment transport processes in the Kärkevagge are investigated concerning their spatial and temporal characteristics due to long–term monitoring. Within this study remote sensing techniques and GIS modelling in connection with geomorphic mapping are applied for identification and characterization of geomorphic process units. Relationships between geomorphometric parameters and slope processes like solifluction, talus creep and rockfall have been analysed. Multitemporal Landsat–TM5 scenes are used as source for landcover characteristics (Normalized Difference Vegetation Index) after preprocessing involving orthorectification and topographic normalization in order to remove possible terrain–induced effects. Additionally, a digital elevation model with a resolution of 20 m for the Kärkevagge catchment is developed and parameters like slope gradient, slope aspect and profile curvature are extracted as input for the analysis of the sediment transport system. The combination of landcover information, geomorphometrical and topological features allows the definition of areas for single process activities. They show specific sediment displacement characteristics depending on material conditions, topological and geometrical features. Geomorphic process units, which show a homogenous composition, are extracted from these available layers.     

Rock slope failure and landscape evolution in the Caledonian Mountains, as exemplified in the Abisko area, northern Sweden

Paraglacial rock slope failure (RSF) is here studied as a locally major contributor to mountain landscape evolution in the Caledonian ranges. Dense RSF clusters exist in Scotland and Norway, but overall RSF distribution in Scandinavia is poorly known. In the Abisko area, air photo scrutiny confirms the reported incidence of sparse but significant RSF. In the Kärkevagge complex, the Rissa RSF is one of the largest in northern Europe, with a scar volume of 42 Mm3. The well–known Giant Boulder Deposit (GBD) is a rock avalanche emanating from the Rissa RSF scar, the interpretation of wholesale valley wall retreat at deglaciation being discounted. In the adjacent valley of Vassivagge, a major RSF on Vuoitasrita has a similar area and morpholocation, but lacks a GBD. It has consumed 5–10% of the relict preglacial mountain surface. Both RSFs are near incipient watershed breaches in valleys which may have undergone vigorous enlargement during the last stadial. Glaciation history may explain spatial incidence as well as neotectonic and other triggers. The localised geomorphic impact of RSF in the Abisko mountains is high by comparison with contemporary slope processes. The cumulative impact of paraglacial RSF over the Quaternary may have been considerable, and RSF may be an indicator of concentrated late–stage glacial erosion.     

Rock slope failure and landscape evolution in the Caledonian Mountains, as exemplified in the Abisko area, northern Sweden

Paraglacial rock slope failure (RSF) is here studied as a locally major contributor to mountain landscape evolution in the Caledonian ranges. Dense RSF clusters exist in Scotland and Norway, but overall RSF distribution in Scandinavia is poorly known. In the Abisko area, air photo scrutiny confirms the reported incidence of sparse but significant RSF. In the Kärkevagge complex, the Rissa RSF is one of the largest in northern Europe, with a scar volume of 42 Mm3. The well–known Giant Boulder Deposit (GBD) is a rock avalanche emanating from the Rissa RSF scar, the interpretation of wholesale valley wall retreat at deglaciation being discounted. In the adjacent valley of Vassivagge, a major RSF on Vuoitasrita has a similar area and morpholocation, but lacks a GBD. It has consumed 5–10% of the relict preglacial mountain surface. Both RSFs are near incipient watershed breaches in valleys which may have undergone vigorous enlargement during the last stadial. Glaciation history may explain spatial incidence as well as neotectonic and other triggers. The localised geomorphic impact of RSF in the Abisko mountains is high by comparison with contemporary slope processes. The cumulative impact of paraglacial RSF over the Quaternary may have been considerable, and RSF may be an indicator of concentrated late–stage glacial erosion.     

Spatial variation of early season surface water chemistry in Kärkevagge, Swedish Lapland

This study examines the spatial variability of early season water chemistry in the arctic-alpine valley of Kärkevagge, Sweden. The data demonstrate the spatially heterogeneous nature of water chemistry and the general patterns of chemical weathering in the valley. Water chemistry in this valley is dominated by two anions, bicarbonate and sulfate. Bicarbonate is derived from the dissolution of atmospheric CO₂ and the weathering of carbonate units in the local metamorphic rocks, while the sulfate is derived from the oxidation of pyrite in the Seve-Koli tectonic nappe. Spatial patterns of chemical constituents reflect the broad effects of local geology on surface water chemistry. In particular, they demonstrate the effects that mineral species present in minor amounts have on basin-wide water chemistry. However, solute flux rates derived from water chemistry and discharge demonstrate less variability.     

Identification of geomorphic process units in Kärkevagge, northern Sweden, by remote sensing and digital terrain analysis

Sediment transport processes in the Kärkevagge are investigated concerning their spatial and temporal characteristics due to long–term monitoring. Within this study remote sensing techniques and GIS modelling in connection with geomorphic mapping are applied for identification and characterization of geomorphic process units. Relationships between geomorphometric parameters and slope processes like solifluction, talus creep and rockfall have been analysed. Multitemporal Landsat–TM5 scenes are used as source for landcover characteristics (Normalized Difference Vegetation Index) after preprocessing involving orthorectification and topographic normalization in order to remove possible terrain–induced effects. Additionally, a digital elevation model with a resolution of 20 m for the Kärkevagge catchment is developed and parameters like slope gradient, slope aspect and profile curvature are extracted as input for the analysis of the sediment transport system. The combination of landcover information, geomorphometrical and topological features allows the definition of areas for single process activities. They show specific sediment displacement characteristics depending on material conditions, topological and geometrical features. Geomorphic process units, which show a homogenous composition, are extracted from these available layers.     

56 YEARS OF SOLIFLUCTION MEASUREMENTS IN THE ABISKO MOUNTAINS, NORTHERN SWEDEN – ANALYSIS OF TEMPORAL AND SPATIAL VARIATIONS OF SLOW SOIL SURFACE MOVEMENT

Solifluction movement rates from 1952 to 2008 for the Abisko region, northern Sweden, have been compiled and analysed through correlation tests and multiple regression. The temporal analysis is based on two datasets ( Lobe11 & gridAB and Line B ) from Kärkevagge. The dataset Lobe11 & gridAB show a strong correlation between movement rates and mean annual air temperature (MAAT) and MAAT is also identified as one of the significant contributing parameters in the multiple regression model. No significant correlations were found for the Line B dataset. The spatial analysis indicates generally higher movement rates in the western part of the region and at lower altitudes mainly between 700 and 900 m a.s.l., but the spatial variability is high. To reduce the influence of the temporal variation the data for the correlation tests of the spatial variations were divided into two parts: 1957 to 1980 and 1981 to 2008. The correlation analysis of the dataset 1957 to 1980 shows a significant negative correlation between annual average movement rates and permafrost probability and altitude. The dataset 1981 to 2008 shows a positive correlation between movement rates and wetness index. It is concluded that movement rates may increase with higher MAAT in the western part of the region (Kärkevagge), the spatial variability of movement rates within the region is very high and that altitude (and/or permafrost) together with wetness index are the main controls on the regional spatial variation. The study highlights the limitations in establishing statistical relationships between movement rates and climate using data from different field empirical studies.     

Snow-avalanche impact landforms, deposits and effects at Urdvatnet, southern Norway: implications for avalanche style and process

An unusual assemblage of landforms and deposits is described from upper Norangsdalen, Sunnmøre region, southern Norway, and interpreted as the product of snow‐avalanche events that vary in magnitude, frequency and debris content. An avalanche impact plunge pool, proximal scar and distal mound are associated with a coarse gravel deposit covering part of the valley floor. Landforms in this debris spread include gravel ridges, boulder lines, beaded ridges, fine sediment banked against and covering large boulders, and gravel clumps. Many of these landforms are aligned, indicating across‐valley transport radiating from the plunge pool. Features were mapped in the field and samples analysed for grain size and heavy‐mineral content. The debris spread is attributed to deposition by high‐energy, debris‐rich snow‐avalanche events that collect debris from large areas of the valley side, lower slopes and plunge pool. Aligned landforms develop through sediment transport in a basal shear zone, and randomly distributed gravel clumps represent melt pits following debris transport in the avalanche body. Air displacement ahead of larger avalanches is thought to have felled and tilted trees on the lower slopes of the distal valley side. Approximate ages of damaged trees allowed estimation of the frequency of snow‐avalanche events: (1) small, frequent events (several per annum) carry debris to the lower valley slopes and the plunge pool; (2) moderate events with an annual to decadal frequency maintain the pool–scar–mound complex; and (3) large, debris‐rich events with a decadal to centennial frequency add material to the debris spread.     

The hydrogeochemistry of the Kärkevagge Valley, Lapland, Sweden

The Kärkejokk (jokk = Lappish for brook) is rich in sulfate and calcium, both elements having been considered enigmatic. To resolve these problems we collected waters at 13 sites during 27 June to 1 September 1996. Nine sites were in the Kärkevagge, and the others in the drainage towards lake Torne Träsk. Rain waters were collected the same period. Conductivity, pH, and temperature were measured in the field, whereas salt load and the elements Na, K, Ca, Mg, S, Si, Fe, Al, Mn, Zn, Sr, and Ba were determined in the laboratory.
Mixing models based on rain water and leaching products of the major bedrocks do not explain observed element patterns except in the lower parts of the jokk. However, oxidation of pyrite has formed acid, sulfate–rich solutions that released Ca and Mg from limestones, and Fe, Mn, Al, and Si, from black shales (Malmsten 1998; Malmsten et al. 2000). Conservative mixing models, using rain water, leached bedrock and pyrite, match the jokk waters quite well, and sulfur isotope data corroborate these findings. The nearby Låktajokk, and Vassijokk also contain much S.
Where these waters debouch they may deposit Si, Al, and Ca, but only little S on various rocks. Total rock analyses, thermodynamic and X–ray data suggest that gypsum, barite, or alunite are not formed in major quantities.
These models show that the hydrogeochemistry of the Kärkejokk may be less enigmatic than often assumed.     

SPATIAL AND TEMPORAL PATTERNS OF TALUS ACTIVITY – A LICHENOMETRIC APPROACH IN THE STUBAIER ALPS,AUSTRIA

Lichenometric measurements using Rhizocarpon ssp. were carried out on 20 talus slopes in the cirques of the Finstertal valley (Austria) at an elevation of 2300–3000 m a.s.l. The aim was to assess activity patterns on selected slopes and between the slopes of the study area, to find evidence of rockfall pulses in the last centuries and to calculate rockwall retreat rates. A calibration curve was derived from five sites of known age and adapted to the prevailing size of talus boulders. We measured the five largest lichens on more than 300 boulders and the percentage coverage of Rhizocarpon‐free clasts on more than 1000 test fields. Most of the investigated talus cones are characterized by moderate rockfall supply, with the apex being more active than the talus foot and moderate redistribution by avalanche and debris flows. Considerably enhanced activity was found under rockwalls influenced by permafrost, particularly on the north faces at an elevation of >2600 m a.s.l. At currently moderately active sites, boulder falls seem to have been slightly more frequent in the late nineteenth and first half of the twentieth century. In positions where permafrost is expected in the rockwalls, a weak maximum in the late nineteenth century and highly active present‐day conditions were found, the latter being assigned to current permafrost melt. Rockwall retreat rates derived from lichen coverage are between 400 and 1500 mm/ka which is in good concurrence with talus volume assessments, but higher than the rates derived from direct rockfall measurements. The rates derived from lichen coverage have to be taken with caution as the effects of debris redistribution are hard to quantify.