Spatial and Temporal Variations of Solifluction and Related

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List of Papers

This thesis is based on the following papers, which are referred to in the text by their Roman numerals.

I Ridefelt H., Boelhouwers J., 2006, Observations on regional variations in solifluction landform morphology and environment in the Abisko region, northern Sweden. Permafrost and Periglacial Processes, 17, 253–266. II Ridefelt H., Etzelmüller B., Boelhouwers J., Jonasson C., 2008 Statistic-empirical modelling of mountain permafrost in the Ab- isko region, sub-Arctic northern Sweden. Norsk Geografisk Tidskrift, 62, 278-289. III Ridefelt, H., Boelhouwers, J., Eiken, T., 2009, Measurement of solifluction rates using multi-temporal aerial photography. Earth Surface Processes and Landforms, 34, 725-737. IV Ridefelt H., Åkerman J., Beylich AA., Boelhouwers J., Kol- strup E., Nyberg R., in press, 56 years of solifluction measurements in the Abisko Mountains, northern Sweden – analysis of spatial and temporal variations of slow soil surface movements. Geografiska Annaler. V Ridefelt H., Etzelmüller B., Boelhouwers J., Spatial analysis of solifluction landforms and process rates in the Abisko Moun- tains, northern Sweden. Submitted to Permafrost and Perigla- cial Processes (under revision). VI Ridefelt H., Etzelmüller B., Boelhouwers J., Local variations of solifluction activity in the Abisko Mountains, northern Sweden. Manuscript.

Reproduction of the published papers is made with kind permission from the copyright holders: Paper I and III © John Wiley & Sons Ltd. Paper II © Routledge Francis & Taylor Group Paper IV© Blackwell Publishing

My contributions to the papers Paper I: Field work, data analysis, writing and discussion in collaboration with Jan Boelhouwers. Paper II: All field work and major part of the writing. Data analysis and discussion in collaboration with co-authors. Paper III: Idea and data analysis, part of the writing and discussion. Photo- grammetrical analysis in collaboration with Trond Eiken. Paper IV: Idea and all data analysis, most of the writing and discussion. Paper V: Part of the idea. Data analysis in collaboration with Bernd Et- zelmüller. Most of the writing. Paper VI: Idea in collaboration with Jan Boelhouwers. Most of the field work, data analysis and writing.

Contents

1. Introduction ...... 9 2. Characteristics of solifluction ...... 11 2.1 The mechanisms of solifluction ...... 11 2.2.1 Frost creep ...... 11 2.2.3 Gelifluction ...... 12 2.3 Solifluction landforms ...... 12 2.4 Environmental and climatic controls on solifluction processes ...... 13 2.4.1 Ground climate ...... 14 2.4.2 Permafrost ...... 16 2.4.3 Topography ...... 16 2.4.4 Vegetation and soil texture ...... 17 3. The Abisko region ...... 19 4. Methods ...... 22 4.1 Field measurements ...... 22 4.1.1 Landform morphometry ...... 22 4.1.2 Grids for solifluction measurements at a local scale ...... 22 4.1.3 Permafrost assessment ...... 23 4.2 GIS-derived environmental parameters ...... 23 4.3 Assessment of long-term movement rates using aerial photography . 24 4.4 Compilation of solifluction data from the Abisko region ...... 25 4.5 Statistical methods ...... 25 4.6 Regionalization of movement rates ...... 26 4.7 Geomorphic work ...... 26 5. Results ...... 27 5.1 Solifluction movement rates ...... 27 5.2 Permafrost assessment ...... 28 5.3 Environmental controls on solifluction ...... 31 5.4 Regionalization of movement rates ...... 32 5.5 Geomorphic work ...... 33 6. Discussion ...... 35 6.1 Regional and local scale – similarities and differences ...... 35 6.2 Comparisons between the different methods ...... 36

6.3 Knowledge and methods ...... 37 6.4 Future outlook ...... 38 7. Conclusions ...... 40 Acknowledgements ...... 43 Sammanfattning ...... 45 References ...... 48

1. Introduction

Environmental controls, spatial and temporal variability in solifluction movement rates and landform distribution are addressed in this thesis based on field studies in the Abisko region, northern Sweden. Solifluction is generally considered the most widespread form of slope movement in cold regions and attains surface movement rates in the order of a few cm per year (French, 2007; Matsuoka, 2001). Studies on slow mass wasting processes have largely focused on movement, mechanisms, internal structure or climatic significance and detailed point-specific monitoring, involving studies at the micro- and meso-scale (e.g. Thorn, 2003). Generally, issues related to spatial scale have been neg- lected in contemporary periglacial geomorphology (e.g. Gamble and Meen- temeyer, 1996; Thorn, 2003). Concerns of current climate change impacts on periglacial regions necessitate landscape-scale assessment of solifluction rates on decadal time-scales and methodological challenges for solifluction movement detection (Matsuoka, 2006). On a regional scale, changes in solifluction movement rates can be expected to have an impact on sediment erosion, storage and sedimentation patterns on slopes and on sediment budgets (Ridefelt and Boelhouwers, 2006). However, complex interactions between ground climate, snow, slope hydrology and vegetation and their influence on solifluction at different scales complicate prediction of solifluction responses to climate change. Also, Harris (1993) suggests that the solifluction activity responses to climate change may be highly site specific. A further considera- tion in solifluction movement assessment is the small annual movement and a potentially large inter-annual variability, which necessitates long monitoring periods (Smith, 1992). There are a limited number of studies of variations of solifluction occurrence and movement rates on a catchment or regional scale (e.g. Rapp, 1960; Price, 1973; Smith, 1987; Douglas and Harrison, 1996; Berthling et al., 2002). The results from these studies show that in general solifluction occurrence and activity vary within the study areas. It is therefore difficult to draw conclusions about the solifluction activity for a larger region based on a limited number of measurements. To address this problem, approaches within Geographical Information Systems (GIS) and remote sensing, in combination with statistical analysis, have been developed to model larger areas with reliable results and without extensive field work (e.g. Atkinson et al., 1998; Luoto and Seppäla, 2002; Hjort et al., 2007). Further, morphometry of solif-

9 luction landforms and the factors which control it are still poorly understood and it is currently difficult to generate testable hypotheses concerning process-form relationships (Hugenholtz and Lewkowicz, 2002). Solifluction rates have previously been measured in northern Sweden, mainly by Rapp in the valley of Kärkevagge, with a complete record from 1952-1960 and complementary measurements made by Åkerman during the 1960s and 1970s (Rapp 1960; Rapp and Åkerman, 1993). Rudberg also made measurements on solifluction lobes in Kärkevagge (Rudberg, 1958). Together, these data demonstrate important slope process activity, with mean surface movement rates varying between 2 and 6.5 cm per year. These measurements were undertaken at the slope scale and are insufficient to explain the regional variability in solifluction movement, resulting landforms and associated environmental controls. In addition, these studies did not include the relationships between different climatic factors and solifluction. The overall aim of this study is to understand and quantify the environmental factors that control the spatial distribution and variability of solifluction occurrence, morphometry and movement rates at different scales in the Abisko region in northern Sweden. Apart from field measurements, this includes statistical spatial modelling, the testing of new methodologies such as the use of aerial photography for long-term assessment of solifluction movement rates, compilation of solifluction data from the Abisko region and the assessment of potentially important environmental factors, such as permafrost. These issues are addressed in six papers with the following focus: • Paper I: Variations of solifluction landform morphometry within the Abisko region and its environmental controls. • Paper II: Assessment of the regional permafrost distribution. • Paper III: Assessment of long-term solifluction movement rates using aerial photography. • Paper IV: Compilation of solifluction data from the Abisko region for environmental controls of movement rates on a regional scale and temporal variations. • Paper V: Spatial modelling of solifluction occurrence on a regional scale, regionalization of movement rates and assessment of geomorphic work. • Paper VI: Local scale variations of solifluction movement, geomorphic work and environmental controls.

10 2. Characteristics of solifluction

2.1 The mechanisms of solifluction The term solifluction has been used with slightly different meanings over the years since it was first established by Andersson (1906). I will use the term solifluction as defined by Matsuoka (2001) and van Everdingen (2005) including the mechanisms of both frost creep and gelifluction. Matsuoka (2001) also includes needle ice creep and plug-like flow in the definition of solifluction, but since these mechanisms are not operating in the study area, these are not considered. Segregation ice formation and subsequent frost heave and thaw consolidation are discussed as these are the essential parts of the frost creep and gelifluction mechanisms. It should be emphasized that the mechanisms often operate in close synergy.

2.2.1 Frost creep Frost creep is the downslope movement of soil particles originating from frost heaving normal to the slope, followed by near-vertical thaw consolidation (Benedict, 1970). Upon thawing cohesion between soil particles may induce retrograde movement (Matsuoka, 2001). Depending on the periodici- ty of the freeze-thaw cycles, frost creep can be subdivided into diurnal frost creep and seasonal frost creep. It occurs in all frost environments and does not require permafrost. Segregation ice formation (and succeeding thawing) is essential for frost creep to occur. Segregation ice is commonly present as ice lenses, which are orientated parallel to the freezing plane at time of formation (Williams and Smith, 1989). Taber (1930) and Beskow (1935) showed that frost heave is mainly due to the freezing of transported water and that the main controlling factors of segregation ice growth are the size and shape of soil particles, the amount of available water, the size and percentage of voids, rate of cooling and the surface load. Regarding moisture, frost heave will be greater in wet or moist situations, if the other conditions are equal (Williams and Smith, 1989). Frost heave also has a very distinctive way of affecting the soil structure and its strength upon thawing, which is related to ice content and moisture supply during thaw (Van Vliet-Lanoë, 1985; 1998). The thickness of the affected material

11 is believed to be important since it has an impact on the shear stresses, which increase with depth (Williams and Smith, 1989).

2.2.3 Gelifluction Gelifluction occurs when a plastic soil layer originates from thawing of segregated ice in seasonally frozen ground and/or inflow of additional water from meltwater or rainfall (Harris, 1993; Matsuoka, 2001). If the meltwater cannot drain away the increased porewater pressure causes a reduction in the frictional strength of the thawing soil. In non-cohesive soils, as silt- and sand-sized fines, shearing is distributed throughout the moving soil mass. Normally these soils have low liquid and plastic limits and are highly dependent on variations in soil moisture (Harris, 1993). Field measurements indicate that gelifluction is dominant at wetter sites, in comparison with frost creep (e.g Washburn, 1967; Benedict, 1970; Jaesche et al., 2003) and movement often occurs when the soil is close to or above its liquid limit (Smith, 1988). The precise mechanisms of gelifluction remain debatable (Kinnard and Lewkowicz, 2005). Harris et al. (1995, 1997, 2003, 2008a) have shown in laboratory studies that when void ratios are high, low shear strengths can for shorter periods be observed immediately behind the thaw front. When thaw consolidation subsequently occurs the void ratio and moisture content are lowered and the soil strengthens. The soil movement may in this context be regarded as a pre-failure strain in the thawing soil (e.g. Harris et al., 1997) and gelifluction has been considered to occur by viscous flow. But Harris et al. (2003) have demonstrated that the gelifluction movement more appears to be like plastic creep. This has been supported by Kinnard and Lewkowicz (2005), who observed that gelifluction events occurred while soil moisture was close to or above the liquid limit of the soil. This would suggest that the soil was close to a viscous state, but the gelifluction peaks were followed by retrograde movement indicating an elasto-plastic process (Kinnard and Lew- kowicz, 2005).

2.3 Solifluction landforms According to the IPA’s Glossary of Permafrost and Related Ground-Ice Terms (van Everdingen, 2005) solifluction landforms can be divided into:

• Solifluction apron: A fan-like deposit at the base of a slope. • Solifluction lobe: An isolated, tongue-shaped feature, up to 25 m wide and 150 m or more long. Fronts covered by a vegetation mat are called "turf-banked lobes" whereas those that are stony are called "stone-banked lobes".

12 • Solifluction sheet: A broad deposit of non-sorted, water- saturated, locally derived materials that is moving or has moved downslope. Sorted and/or non-sorted stripes are commonly associated with solifluction sheets. • Solifluction terrace: A low step, or bench, with a straight or lobate front. Those covered with a vegetation mat are called "turf-banked terraces"; those that are stony are called "stone- banked terraces". There is a wide range of terminology in relation to solifluction landforms. I partly follow IPA’s terminology, but mostly consider the terminology commonly used (e.g. Benedict, 1970; Washburn, 1979; French, 1996; Mat- suoka, 2001), in which features produced by solifluction are grouped into lobes and terraces. It is important to be aware that there are other terms being employed for similar features depending on the author (e.g. solifluction tongue, Rudberg, 1962; solifluction steps, Walsh et al., 2003). This leads to a terminology that can often be confusing (Douglas and Harrison, 1996).

2.4 Environmental and climatic controls on solifluction processes Even though knowledge is not complete in detail on what environmental factors actually control solifluction rates, it is clear that climate, hydrology, geology and topography all play a role (Matsuoka, 2001). Environmental factors affect the mechanisms and rates of solifluction in different ways and their importance vary from site to site, between different regions (Benedict, 1970; Williams and Smith, 1989) and between different climatic zones (e.g. Matthew et al., 1993). It is also difficult to make quantitative conclusions about the relative importance of the environmental factors, as the interaction between these factors is very complex (Matthews et al., 1993). Change in scale also changes the relevant environmental parameters controlling the spatial variability (Turner et al., 1989). However, how different environmental parameters influence solifluction distribution and rates at different scales is rarely discussed as deduced from the methodologies used in different studies. Many authors have made suggestions on the controlling environmental factors in specific areas or regions (e.g. Matthew et al., 1993; Åkerman, 1996; Auzet and Ambroise, 1996; Hugenholtz and Lewkowicz, 2002, Matsuoka et al., 2005) without referring to the scale of measurement. Table 1 summarizes some of the studies in relation to the scale of the studies with special reference to the local and regional scale. According to Ta- ble 1 soil moisture, soil texture and ground temperature regime (reflected in permafrost conditions and freeze depths) are important factors at both local and regional scales. Vegetation types and patterns only seem to be of impor-

13 tance on a local scale, which is also valid for the effect of snow cover (thickness and duration) and snow patches. MAAT and aspect are important on a regional scale.

Table 1. Environmental factors that control solifluction at a local and regional scale according to the literature. Local scale Regional scale Soil moisture (Smith, 1987, 1988; Price, 1990; Soil moisture (Benedict, 1970; Matthew et Jaesche et al., 2003) al., 1993; Åkerman, 1996; Ridefelt and Boelhouwers, 2006; Matsuoka, 2005) Snow cover (Hugenholtz and Lewkowicz, Snow cover (Ridefelt and Boelhouwers, 2002; Jaesche et al., 2003) 2006) Snow patches (Williams, 1957; Hugenholtz MAAT (Matthews et al., 1993) and Lewkowicz, 2002) Freeze/thaw depth (Smith, 1988; Price, 1990; Freeze/thaw depth (Gamper, 1983; Mat- Hugenholtz and Lewkowicz, 2002) thews et al., 1993; Jaesche et al., 2003) Freeze/thaw frequency (Matsuoka, 2005) Soil texture (Perez, 1988; Holness, 2001; Soil texture (Douglas and Harrison, 1996; Hugenholtz and Lewkowicz, 2002; Kinnard Åkerman, 1996; Holness, 2001; Ridefelt and Lewkowicz, 2006) and Boelhouwers, 2006; Matsuoka, 2005) Vegetation (Ballantyne, 1986; Price, 1990; Hugenholtz and Lewkowicz, 2002; Douglas and Harrison, 1996) Topography Slope angle (Åkerman, 1996) Topography Slope angle (Benedict, 1970; Holness, 2004; Matsuoka, 2005) Aspect (Douglas and Harrison, 1996) Altitude (Holness, 2004; Boelhouwers, 2006)

The relevant environmental parameters that emerge from Table 1 are discussed in the following section. Inevitably the different factors, irrespective of scale, are not always possible to separate since they strongly interact and therefore will appear in several sections.

2.4.1 Ground climate Soil moisture is essential in all environments where solifluction occurs (e.g. Benedict, 1970; Matsuoka, 2001; Jaesche et al., 2003; Kinnard and Lewko- wicz, 2005). It controls segregation ice growth and soil saturation potential and is a function of precipitation, net radiation, temperature and soil texture and structure. Soil moisture has an effect upon the soil freeze-thaw regime through changes in the thermal properties. In the Alps late summer precipitation is of importance for providing soil moisture during freeze up and thaw (Jaesche et al., 2003). High moisture availability during the snow melt period can maintain a high groundwater level until autumn and enhance potential diurnal freeze-thaw action and also increase seasonal frost heave (Bene- dict, 1970). This might enhance both diurnal and annual frost creep and ge-

14 lifluction. Low rates of movement may be due to either reduced moisture availability or rapid drainage of the ground during the snow melt period (Douglas and Harrison, 1996). On a local scale late-lying snow patches are important in contributing with meltwater to the seasonally thawing ground, which may induce mass movement if the debris is saturated (Harris, 1972; Embleton and King; 1975; Smith, 1988). Williams (1957) found that terraces were associated with late-lying snow and that the snow patches melted from the underside providing meltwater downslope. In Scandinavia solifluction rates seem to respond most strongly to differences in soil moisture contents during the spring and summer thaw (Mat- thews et al., 1993). This results from increased winter snowfall, which re- duces frost penetration rates leading to a greater formation of segregated ice during autumn freeze-back. As a consequence, the soil moisture content will be higher during the succeeding thaw phase (Matthews et al., 1993). On a local scale, late-lying snow patches are important in contributing with meltwater to the seasonally thawing ground. Solifluction is often found downslope from snow patches, which provide meltwater downslope when melting from the underside (e.g. Nyberg, 1991; Hugenholtz and Lewkowicz, 2002). The snow cover thickness and duration exerts control on solifluction by its insulation effect, thereby impeding frost penetration and also by the tim- ing of snow melt, with moisture supply to the soil (Hugenholtz and Lewko- wicz, 2002). In the Alps the development of snow cover, especially during early winter snowfalls, also controls the seasonal frost depth and thus the solifluction potential (Jaesche et al., 2003). A threshold relationship may exist, with a minimum of late-winter snow required to provide moisture for spatially differentiated solifluction during the melt season in the arctic environment (Hugenholtz and Lewkowicz, 2002). On a regional scale winter frost penetration, often as a function of snow thickness (Jaesche et al., 2003), seems to be a major controlling factor in the Alps (Gamper, 1983; Matthews et al., 1993). Harris et al., (2008b) observed large spatial variation in the frost depths due to differences in snow cover thickness. Gamper (1987) found a strong correlation between mean winter air temperatures and solifluction in the Alps. But in a more recent study from the Alps no such correlation could be established from a 13-year record of solifluction movement rates (Jaesche et al., 2003). Ground temperature has, along with soil moisture, an effect upon the formation of ice segregation and saturated conditions (Auzet, 1996). Impor- tant controls on the ground temperature are vegetation type, snow and bare soil (Williams and Smith, 1989). Variations in ground temperature govern the number of frost cycles, freezing and thawing rate and the onset of snow melt and freezing. Frozen ground can be divided into two major groups; seasonally frozen ground and permafrost (Williams and Smith, 1989). From a laboratory study

15 Harris et al. (2008a) have recently shown that in seasonally frozen ground frost heave did only occur during winter frost penetration and ice content decreased with depth. But for permafrost ground frost heave also occurred during summer thaw phases as a result of summer rainfall.

2.4.2 Permafrost Permafrost is widespread in periglacial areas. Generally, the local permafrost condition is more relevant than the regional permafrost conditions in terms of its influence on solifluction processes (Matsuoka, 2001). Permafrost creates an impermeable layer which prevents meltwater to percolate into the ground and, as such, it contributes to water saturation of the ground (e.g. Embleton and King, 1975, Matsuoka, 2001). Surface movement rates are lower on permafrost sites than at non-permafrost sites. High surface rates are usually associated with a high frequency of diurnal freeze–thaw cycles, but maximum depth of movement is largest in the cold permafrost zone and most rapid denudation is where slopes are underlain by warm permafrost (Matsuoka, 2001). However, Harris et al. (2008a) suggest that sediment transport by solifluction is possibly much larger in cold permafrost regions than in warm permafrost or non-permafrost regions. This is because solifluction will be favored by the melting of segregated ice or, as during permafrost degradation or climate warming, by the complete thaw of the ice-rich tran- sient layer. In contrast to this, data from Marion Island (sub-Antarctic) and Abisko (sub-Arctic, northern Sweden) suggest much higher rates of denudation in the sub-Antarctic environment dominated by diurnal frost activity than in the sub-Arctic environment dominated by seasonal frost (Davis and Ridefelt, unpublished data).

2.4.3 Topography Topography has, through the net radiation balance, a major influence on air and ground temperatures, precipitation, snow cover distribution and duration. Aspect, slope angle and altitude are main controls on the variations in incoming radiation, whereas slope curvature controls flow acceleration and erosion/deposition rates (e.g. Lane et al., 1998). Slope angle directly influences solifluction movement through the gravi- tational downslope force component and rarely occurs at slope angles less than 5° (Douglas and Harrison, 1996). In lower latitude alpine areas the influence of slope gradient is often masked by the spatial variation in other factors such as freeze-thaw frequency, surface texture and moisture distribution (e.g. Benedict, 1970). Åkerman (1996) observed very little influence of slope angle in a regional study on movement rates of solifluction on Spits- bergen. But, on a local scale good correlations were found between slope

16 angles and movement rates of non-vegetated solifluction lobes and non- sorted steps (Åkerman, 1996). The importance of slope aspect has been noted in a regional scale study by Smith (1988) in the Canadian Rocky Mountains, where significantly higher movement rates were detected on sites with north to east aspects. Douglas and Harrison (1996) observed that aspect seemed to operate on a broader scale, rather than at a local level in southeast Iceland and that turf- banked terraces were best developed at wind-exposed sites. Ballantyne and Harris (1994) came to a similar conclusion, but their observations in the northern Highlands of Scotland showed that 90% of the turf-banked terraces occupied lee slopes.

2.4.4 Vegetation and soil texture The role of vegetation is more unclear, although it is mentioned by many as a possible controlling factor (Gamper, 1983; Matthews et al., 1993; Pissart, 1993; Douglas, 1996; Matsuoka, 2001). Vegetation often interacts in a complex manner with topography and snow cover, soil conditions and hydrology (Williams and Smith, 1989). One of the main effects of vegetation is its insu- lating properties (Kane, 1997). But depending on the type of vegetation the indirect influences of vegetation vary considerably (Tricart, 1969). The buf- fering effect of different types of vegetation can be attributed to the influence of vegetation on snow distribution, thickness and longevity (Liston et al. 2002). Moss and organic matter in the soil also increase the soil water holding capacity. In permafrost environments thick moss carpets and organic soil horizons decrease active layer thickness (Kane, 1997). Liston et al., (2002) concluded from an experiment on arctic tundra that an increase in the distribution and height of shrubs leads to less snow redistribution by the wind and less snow lost to sublimation during wind transport. In the Alps vegetation helps to insulate the soil, so as to reduce the depth of frost penetration and reduce rates of solifluction by gelifluction, but pro- moting frost creep (Gamper, 1983; Matthews et al., 1993). In Scandinavia, the relationship between the rate of solifluction and vegetation appears to be more complex. On the local scale the vegetation free surfaces are also believed to favor the development of active landforms related to solifluction processes (Doug- las and Harrison, 1996). The importance of vegetation locally is also supported by Josefsson (1990), who attributes local variations in ground temperatures in the Abisko Valley to different vegetation types. Benedict (1970) pointed out the importance of soil texture and this has also been demonstrated in a laboratory experiment by Harris (1995). Harris’ (1995) results showed that frost heave and surface downslope movement were greater in silt-rich soils than in sandy soils. Silt-rich soils are prone to gelifluction because of their susceptibility to ice segregation during freezing

17 and because drainage of excess soil water is slow during thawing (Harris, 1993). Further, moisture thresholds for plastic deformation vary with soil texture, where sandy and silty soils have low liquid and plastic limits (Har- ris, 1977). Douglas and Harrison (1996) argue that coarse (sandy to stony) soils drained relatively rapidly during the period of snow melt which resulted in reduced rates of solifluction.

18 3. The Abisko region

The Abisko region (68°21'N, 18°49'E) is situated within the Scandinavian mountain range, the Caledonides, in northern Sweden, approximately 200 km north of the Arctic Circle. It is dominated by north-south orientated valleys and the summits in the region reach around 1400 m a.s.l. (Fig. 1). Sev- eral glaciations have occurred in the north-west of Sweden during the Qua- ternary, with mountain ice sheets dominating between 0.7 and 2.0 million years ago and Fennoscandian ice sheets developing over the last 0.7 million years ago. During glacial phases cold-based ice has formed on upland surfaces and preserved these. Extensive relict non-glacial surfaces are located at mid-elevations around 1000 m a.s.l. (Kleman and Stroeven, 1997; Goodfel- low et al., 2008). Goodfellow et al. (2008) suggest that the summits in the study region have not undergone significant glacial erosion. The region was chosen because of its variations in climate and topography within in a restricted area (approximately 150 km2), which make this region interesting when studying spatial variation of natural processes. Fur- ther, there is documented evidence of solifluction activity in the region (e.g. Rapp, 1960; Rudberg, 1962; Nyberg, 1991). Good research facilities and long climate records further support the selection of the study area.

Figure 1. The study region extending from Kärkevagge in the west to Abisko in the east.

The Abisko region experiences an oceanic sub-Arctic climate in the west, but becomes significantly drier towards the east. Annual precipitation at Katterjåkk to the west is 848 mm, while only 304 mm is received in the Ab- isko valley to the east. Even though Björkliden is situated only c.10 km west of Abisko, it receives almost twice as much precipitation (Fig. 1). This af- fects the general soil moisture and snow conditions in the study area. Only small differences in mean annual temperature can be observed, but increased continentality towards the east results in higher temperature amplitudes (Åkerman, 2005). The geology in the area is dominated by mica schists and calcite marble, except for the valley of Kärkevagge which is dominated by quartzitic and phyllitic rocks and other banded tectonites (Kulling, 1964). Till is the most common regolith material in the area, but there are also some glacifluvial deposits. At higher altitudes the regolith is thin and uncohesive (Rodhe et al., 1999). The vegetation in the valleys and on lower slopes is dominated by grass heath, dry heath and meadow with low and tall herbs. The treeline is generally around 650 m a.s.l., but reaches 700 m a.s.l., on south-facing slopes. Above the treeline dwarf willows and meadows with tall herbs dominate and are succeeded by fresh willow and dwarf birch rich heath. With increased altitude the vegetation gradually becomes dominated by dry heaths and meadows with low herbs, which above 1000 m a.s.l. changes to grass heath (An- dersson et al., 1985). On the summits of Mt Låktatjåkka and Mt Njulla the

20 vegetation is sparse and the regolith thin. The east-facing slopes are normally in the lee of dominant westerly winds and sustain preferential snow accu- mulation relative to the wind exposed west-facing slopes (Darmody et al., 2000). Solifluction occurs throughout the region and the dominating landforms are turf-banked lobes and terraces (Ridefelt and Boelhouwers, 2006). On summit areas there are also stone-banked lobes and non-sorted sheets. In the NW-SE oriented valley Kärkevagge, located in the west of the region, snow accumulates on the northeast-facing side of the valley. It is also on these slopes where most solifluction occurs. The dominant forms in the valley are turf-banked lobes and terraces. The Låktatjåkka valley is oriented parallel to the Kärkevagge valley. It has shorter slopes than Kärkevagge and a less steep east-facing slope. Solifluction landforms are generally smaller in this valley and patterned ground is locally present; large solifluction forms occur on the west-facing slope. On the upslope southern end of the valley lobe- shaped solifluction features are present. Dominant landforms on Mt Låktatjåkka are stone-banked lobes, non-sorted stripes and non-sorted sheets. At lower altitudes on Mt Njulla and in the Björkliden area turf- banked lobes are common. In the Latnjajaure area, situated 15 km west of Abisko, slopes are steep, the valley floor is flat and dominated by a lake and regolith is shallow (Beylich, 2008). Solifluction occurs on west-facing slopes, since the east-facing slopes are very steep and mainly consists of rockwalls (Beylich, 2008).

21 4. Methods

4.1 Field measurements The field measurements were initiated during the summer 2003 and termi- nated in 2008. In addition to the measurements described below solifluction landforms were mapped in the field during the years 2007 and 2008. This was based on visual observations for most parts of the region and complemented with aerial photo analysis and the use of an unpublished geomorpho- logical map.

4.1.1 Landform morphometry Morphometry of solifluction landforms at ten sites was assessed in the field, measuring tread widths and lengths and riser heights (paper I). The sites were distributed within the region from east to west according to the moisture gradient and were also selected based on differences in elevation and aspect.

4.1.2 Grids for solifluction measurements at a local scale Grids for measuring ground surface movement rates were set up at ten sites within the study region (paper V and VI). These covered both solifluction landforms and adjacent ground. The grids also included differences in the environment, such as slope gradient, stoniness on the surface, vegetation cover and moisture differences at the surface. Wooden dowels of 20 cm length were used for measurement of surface movement rates and frost heave. A reference point consisting of a 0.8 m long aluminum-pole with a diameter of 10 mm was inserted into stable ground at the back of a block or at depths below 0.6 m where movement should not occur. A string was at- tached to the poles, which served as reference line and measurements of displacement were done using a steel tape. To create digital spatial models of the grids a Total Station (Trimble, Geodimeter®) connected to a handheld computer (PSION Workabout®) equipped with the software Geodos© (paper VI). The software was also used. Locations of each dowel, the boundaries of the solifluction forms, blocks, permanent water and stream channels were recorded.

22 Soil moisture measurements were made at every wooden dowel using a TDR-probe (Theta Probe ML2, Delta-T devices, Cambridge). The vegetation within the grids was characterized through three classes: mosses/lichens, herbs (shrubs) and grasses. The percentage cover of each class was visually estimated within a circumference of 0.5 meter around selected markers at regular intervals. The dominating grain size fractions of soil material were assessed by sampling mineral soil at a depth of c.20 cm at regular intervals within the grids. The soil samples were dried, weighted and sieved. To ana- lyze the silt and the clay content in the fraction smaller than 0.063 a laser granulometre was used (CILAS Granulometer 715, Marcoussis, France).

4.1.3 Permafrost assessment The potential permafrost distribution was assessed in March 2005 and 2006 using the bottom temperature of snow cover (BTS) method (Haeberli, 1973; Hoelzle, 1992) (paper II). Haeberli (1973) introduced the method, to indicate possible permafrost occurrence in mountainous areas and it has been used in numerous studies (e.g. Hoelzle, 1992; Isaksen et al., 2002; Lewkowicz and Ednie 2004). The method was developed for the Alps, but has also been used successfully in the Norwegian mountains (e.g. Isaksen et al., 2002; Heggem et al., 2005). The values of BTS correspond to different probabilities of permafrost occurrence as follows: BTS <-3°C permafrost probable; -3°C to - 2°C permafrost possible and >-2°C permafrost not probable (Haeberli, 1973). These thresholds values have been questioned recently (Bonnaventure and Lewkowicz, 2008), who recommended that the BTS measurements should be complemented by extensive ground truthing. In the present study, the BTS was supported by automatically recorded ground temperature measurements, which were used to derive an alternative permafrost assessment by calculating the mean annual ground temperature and the frost number (Nelson and Outcalt, 1987).

4.2 GIS-derived environmental parameters To complement the data collected in the field, topography parameters were derived from a 50 m DEM (Lantmäteriet©), using ArcGIS®9.2 and TAS 2.0.9© (paper II, IV and V). The parameters elevation, slope gradient, slope curvature (total, plan and profile), standard deviation of slope curvature, mean upstream flow length, downstream flow length, wetness index, potential incoming radiation (PR) and duration of sun hours are assumed to be important for the distributional pattern of solifluction (see section on environmental controls). Further, a normalized difference vegetation index (NDVI) was used for assessing the differences in vegetation cover (paper V). An index for the snow cover was also developed, primarily based on the

23 slope gradient, aspect and the wind direction. This delimits lee and wind- faced areas. A redistribution of + 25% on lee slopes and -25% on wind- facing slopes was assumed. A trend surface was created based on precipitation data from four weather stations in the region (paper V).

4.3 Assessment of long-term movement rates using aerial photography A new methodology of using aerial photography for assessing long-term movement rates was developed (paper III). Two pairs of overlapping aerial photographs covering the Kärkevagge and Låktatjåkka valleys were selected based on highest available resolution and longest time span between the photographs (1959 and 2000). The flight height of the selected images is c. 4600 m above the terrain and the pixel resolution is c.0.5 m. The original films were scanned with a resolution of 15 microns, corresponding to a Ground Sampling Distance of 0.46 m. A 50 m Digital Elevation Model (DEM) (Lantmäteriet©) was used to create orthophotos with a resolution of 0.5 m from the aerial photographs. The Root Mean Square Error (RMSE) was used to estimate the error in the analysis. The outline of the riser contact with the surrounding slope was digitized in ArcGIS® 9.2 on both orthophotos using as much zoom as possible. Two different approaches, the flow direction method and the front line method, were explored to estimate displacement of the lobe front and one approach to estimate volume of the material involved. The flow direction method is based on the assumption that the direction of the movement of the landforms follows the steepest descent. The flow direction is calculated from a raster DEM using the flow direction function implemented in ArcGIS®. Displace- ment measurements were made at c.1m interval along the outline of the forms identified in the photographs. The front line method defines the direction of the movement as perpendicular to the front outline of the form. To calculate the volume flux of displaced material using the two orthophotos the height of the risers needed to be measured in the field at several places at each form. The area of the morphometry change was calculated by digitizing polygons, which follow the outline of the forms on the two orthophotos. To calculate the volume of displaced material at each form, the areas of the polygons were then multiplied with the average differences in riser height at each form.

24 4.4 Compilation of solifluction data from the Abisko region Rates of solifluction surface movement have been measured in the Abisko region since the 1950’s, especially in the valley of Kärkevagge. This data constitutes a unique database of solifluction movement rates, which are compiled and analyzed in paper IV. The first measurements from the 1950’s are predominantly from Kärkevagge (Rapp, 1960; Rudberg, 1962). Mea- surements in Kärkevagge continued until the late 1970s (Rapp and Strömqu- ist, 1979; Rapp and Åkerman, 1993). Åkerman continued the measurements, with the latest readings from 2002 and these previously unpublished results are presented in paper IV. Measurements have also been made in the areas of Låktatjåkka, Njulla, Björkliden, Nissunvagge and the Latnjavagge drainage basin (Nyberg, 1991, 1993; Beylich, 2008). As presented in this thesis, Ride- felt and Boelhouwers measured solifluction movement rates at eight sites within the region from 2004 until 2008 (papers IV - VI).

4.5 Statistical methods The statistical analysis was made in order to explore the relationships between solifluction and the environmental factors that potentially control this process. Solifluction as dependent variable was characterized through morphometry (paper I), movement rates (paper IV, V and VI) and occurrence (paper V). The analysis was made using parametric and non-parametric correlation analysis depending on the distribution of the data used, multiple regression (paper IV), logistic regression (paper II and V) and geographically weighted regression (GWR) (paper II and V). GWR was introduced into geomorphology by Atkinson (1998) in a study of riverbank erosion, but has not yet been applied in periglacial geomorphology. It is the analysis of spatially varying relationships (non-stationarity) and makes it possible to detect and map local trends. The method can be used as an exploratory tool to detect locations that might be of special interest, to determine if spatial non-stationarity is present in relationships of spatial data or to build models (Fotheringham et al., 2002; Brunsdon et al., 1999). The GWR model (Equation 1) is an extension of a global regression model:

i = 0 (ui,vi)+ k k (ui,vi)k+ i (Equation 1)

th where (ui,vi)are the coordinates of the i point in space and k (ui,vi) is the realization of the continuous function k (u,v)at the point I, k is the independent variable and i is a random error term .

25 To evaluate if the variation is a reflection of non-stationarity the interquartile range of the local estimates can be compared to the standard error of the global model (Fotheringham et al., 2002). When applied in paper II and V a logistic GWR model (Fotheringham et al., 2002) was used.

4.6 Regionalization of movement rates An attempt was made to regionalize the variations in movement rates within the Abisko region based on movement rates measured in the field (paper V). Two different approaches were tested. First, the topographic and environmental variables retained in the global logistic regression model were used together with the most significant result from the correlation analysis to per- form an unsupervised maximum likelihood classification (Jensen, 1996). In combination with the field measured movement rates this classification was used to regionalize the annual average movement rates (activity map 1). The second approach was based on the linear relationship between probability of solifluction occurrence and movement rates of the forms. The relationship was used to interpolate movement rates within the region (activity map 2).

4.7 Geomorphic work Geomorphic work, defined as a measure of erosion intensity (Equation 2, Caine, 1976) was calculated for valley slopes (paper V) and for the grid areas (paper VI) and includes values for both solifluction landforms and adjacent areas with no developed landforms.

E = V g(d sin) (Equation 2)

where V is the volume, is the density, g is the acceleration of gravity, d is the slope distance and is the slope angle.

For further details on the calculations see papers V and VI. For the estimation of the geomorphic work on the valley slopes (paper V) the movement rates used in the volume calculation are based on the linear relationship between probability of solifluction occurrence and the average of movement rates for both developed forms and ground with no developed forms (paper V). For the estimation of the geomorphic work within the grid areas (paper VI) the average annual movement for each grid was used, including movement of both landforms and the adjacent ground.

26 5. Results

5.1 Solifluction movement rates Measurements of solifluction movement rates, based on different methodologies, are presented in paper III to VI. Below an attempt is made to compare the results, as reflected by the different methodologies. It should be noted that measurements from the photo analysis represent movement rates of the lobe front, whereas the field measured values represent measurements made at the tread surface of the forms. There is also a temporal variation in the data set. Data from the photo assessment gives the average over 41 years, whereas the data from the field measurements is based on an average over four years (2004 to 2008) and the data used in the compilation paper vary for each study (paper IV). Bearing these differences in mind, maximum and minimum average rates for different sites are presented in Table 2. Maxi- mum rates of individual markers are not considered, nor are the minimum rates of the individual markers, which most likely will correspond to 0 at most sites. This is motivated by the fact that individual markers can either be outliers or represent peaks of variations which are not spatially or temporally representative of the site.

Table 2. Average (avg) solifluction movement rates in the Abisko region estimated by different methods. For the Mt Låktatjåkka site the data from the compilation study refers to “stone stripes” , whereas data from field measurements refers to non-sorted sheets. At the Njulla W site the field measurements refer to measurements from both a turf-banked solifluction lobe (max rate) and to small bare lobes superimposed on a larger lobe (min rate). Site/area Aerial photo assessment Field measurements Data compilation (avg mma-1) (avg mma-1) (avg mma-1)

Max Min Max Min Max Min Kärkevagge 63 20 60 19* 101 4 Låktatjåkka 102 15 60 6.3 - - Valley Mt Låktatjåkka - - 21 2.1 9 2 Njulla W - - 24 5.4 25 25 Mt Njulla - - 14 0 50 13 * Solifluction terraces are not considered, since these were not included in the aerial photo assessment or the data compilation.

27 For Kärkevagge similar values are found between the three studies. Maxi- mum rates are similar for the photo assessment (lobe fronts) and the field measurements (grid measurements on tread). Field measurements presented in the compilation study suggest even higher maximum rates from solifluction lobe treads (Rapp and Åkerman, 1993). The values compared here are not for the same lobe. However, the field measured lobes are located relatively close to each other. The two lobes from the photo analysis, which have the maximum value of 63 mma-1, are located much further away in the valley, c.700-1200 m from the field measured lobes. Similarly, the lobes in the Låktatjåkka valley reported in Table 2 are located relatively far away from each other (c.1000 m) and on different aspects of the valley (N-facing and W-facing). The maximum values for the lobe front (photo analysis) are much higher than the maximum values for the tread (field measurements). At Mt Låktatjåkka the measured sites are probably in close proximity to each other, but the exact location for the stone stripes from the compilation study is unknown. Here, two different landforms, non-sorted sheets and stone stripes, are compared. The non-sorted sheets show the highest maximum movement rate, but there is a large difference in time between these measurements (c.40 years). For the Njulla W site the values compare very well for the two different studies (24 and 25 mma-1), but for the Mt Njulla sites the values are different (maximum rates of 14 and 50 mma-1 respectively). But again these sites are not located in close proximity, with an altitude difference of c.140 m, and the landform types are reported as “sheets” and “small bare lobes” respectively. Overall it can be concluded that there is a variation in the results from the different methods. This is to be expected where results are based on different methods, but it is also true for the results of the field measurement and the data compilation. Only one area, the western slope of Mt Njulla (Njulla W), shows similar results from the field measurements and the data compilation, even though there is a long time span between these measurements.

5.2 Permafrost assessment For the permafrost modelling of the region the result of the GWR analysis suggested that a division of the region into two subregions may be adequate. The interquartile range was equal to two times the standard error and thus there is no strong evidence of non-stationarity; neither no clear evidence of stationarity. In this analysis all local estimated coefficients and constants of the logistic GWR model were significant above the 1.96 level using a 2- tailed pseudo t-test, except the values at Riksgränsen, which were excluded (Fig. 2). The coefficients and constants were divided into two classes using the natural breaks method in ArcGIS® 9.2. Two global logistic regression models were created based on the results in Figure 2, considering the possi-

28 bility of non-stationarity between the Njulla-Slåttatjåkka sub-region in the east and the sub-region between Riksgränsen and Björkliden (referred to as Riksgränsen-Låktatjåkka-Björkliden). The constant value (-2.90) and the coefficient estimate (0.006) in the global model were much closer in values to the constant and coefficient estimate for the western sub-region (-5.15 and 0.005) than for the Njulla-Slåttatjåkka sub-region (-16.54 and 0.02 for elevation) (Table 3). This shows that a single global model of the whole region would have masked the difference in the permafrost-elevation relationship in the Njulla-Slåttatjåkka sub-region.

Figure 2. The spatial variation of the estimated local coefficients and constants in the logistic GWR model of the relationship between elevation and BTS data points. Each colour (grey and white) corresponds to two values representing the range of the constant and coefficient estimates.

The models used elevation as independent variable for the Riksgränsen- Låkatjåkka-Björkliden sub-region and elevation and summer PR for the Njulla-Slåttatjåkka sub-region (Table 3). All independent variables included in the models were significant, but the Nagelkerke r2-value was rather low (Table 3).

29 Table 3. Equation constants and coefficients, based on the global logistic regression and degree of explanation. The constants and coefficients are all significant within the 0.05 confidence level. Topographic St. St. Nagel- Site Con- Coef- kerke Parameters stant dev. ficient dev. r2 Njulla-Slåttatjåkka Elevation 0.02 0.01 -16.54 7.85 0.23 0.34 0.17 PR summer Riksgränsen- Låktatjåkka-Björkliden Elevation -5.15 1.20 0.005 0.00 0.24 Entire region Elevation -2.90 4.3 0.006 0.00 -

In the western part of the region the models showed probabilities >0.50 for permafrost at elevations above 1025 m a.s.l., and >0.8 at 1300 m a.s.l. In the eastern part of the region a probability >0.8 was found at 850 m a.s.l. on the northeast- and east-facing slopes, while a similarly high probability was found at 1000 m a.s.l. on the west-facing slopes and at 1100 m a.s.l. on the south-facing slopes (Fig. 3).

Figure 3. Interpolated probabilities of permafrost based on the global logistic regression models for the sub-regions Riksgränsen-Låktatjåkka-Björkliden and Njulla- Slåttatjåkka.

30 5.3 Environmental controls on solifluction In Table 4 the environmental controls that emerged from different correlation tests and models of solifluction occurrence, morphometry and movement rates are presented. Vegetation is important both on a regional and a local scale. This is expressed through the NDVI, which has the strongest influence on the occurrence of turf-banked lobes on a regional scale (paper V). Different vegetation types also have an influence on variations in movement rates on the local scale, but the importance of different vegetation types varies from site to site (paper VI). Also, soil moisture is important on both scales and has an influence on the occurrence, morphometry and movement rates. On a regional scale elevation/permafrost is of importance, but has no influence on the local scale. Regarding the influence of topography on a local scale, it is instead slope angle which has an importance at some sites (paper VI). Slope angle is also of importance on a regional scale for the solifluction occurrence (paper V). The percentage of fine material has some influence on the solifluction morphometry (paper I), but did not have any influence on the movement rates on a local scale (paper VI). For the solifluction occurrence model it was not included as a parameter. MAAT, freeze start and annual precipitation were identified as having an influence on the annual temporal variations of movement rates.

Table 4. Environmental and climatic parameters influencing solifluction occurrence, morphometry and movement rates as indicated by the statistical analysis. LR refers to a parameter retained in a logistic regression model, while MR refers to a parameter retained in multiple regression model. The asterisk symbol (*) indicates Spearman’s correlation test, where *= 0.05, **= 0.01, and ***=0.001 confidence level. Solifluction Solifluction Solifluction movement rates Parameter occurrence morpho- Local Regional Temporal metry scale scale change NDVI/Vegetation ** LR St Dev curvature ** PR (annual) ** LR Wetness index/Soil moisture * LR *** * * Slope angle ** LR * Elevation/permafrost ** LR *** * Fraction of fine material ** MAAT * MR Freeze start MR Annual precipitation MR Snow index ** Duration sun hours ** Curvature/profile curvature **

31 5.4 Regionalization of movement rates In the unsupervised classification three clusters (referred to as class 4, 6 and 7) corresponded to areas dominated by solifluction landforms (activity map 1, Figure 4). For the regionalization of the sediment movement rates class 4 corresponds to one site with movement measurements, class 6 to four sites and class 7 to one site. According to this classification the highest annual movement rates, 41 mm, are found at the highest elevations in the valleys. Annual movement rates of 9 to 19 mm dominate in the lower parts of the valleys.

Figure 4. The three classes retained from the unsupervised classification based on NDVI, PR annual, elevation and duration of sun hours and the corresponding movement rates.

The regionalized annual average movement rates of solifluction based on the linear relationship between average annual movement rates of the forms and the probability of solifluction occurrence for the same sites show the highest movement rates on the east-facing slopes of Kärkevagge and Njulla (activity map 2, Figure 5). Apart from sharing the same aspect, these slopes do not have similar environmental characteristics.

Figure 5. Regionalized annual movement rates of solifluction based on the linear relationship between movement rates and probability of solifluction occurrence.

5.5 Geomorphic work The geomorphic work calculated for the valley slopes is largest on the east- facing slope of Kärkevagge with a magnitude of 7 MJa-1km-2 and shows a decrease towards the east of the region with the smallest value, 0.6 MJa-1 km-2, for the east-facing slope of Gohpascorru (Table 5). For the grid areas the calculations show the same pattern. The numbers for both calculations correspond well for the site with the largest work, Kärkevagge W1, and for the site with the smallest work, Gohpascorru.

33 Table 5. Geomorphic work calculated for valley slopes (paper V) and for grids areas (local scale, paper VI). The work includes both solifluction forms and areas with no forms. Geomorphic Geomorphic work Area work Area Site (valley slope) (km2) (local) (km2) MJa-1km-2 MJa-1km-2 Kärkevagge W1 7.0 1.15 6.2 0.0042 Kärkevagge W2 Kärkevagge E 3.2 0.85 1.7 0.0057 Låkta valley W-facing 0.7 0.47 2.1 0.0043 Låkta valley E-facing Gohpascorru 0.6 1.14 0.61 0.0031 Njulla W-facing 1.5 1.93 Mt Låktatjåkka - - 0.11 0.00050 Mt Njulla - - 0.13 0.00043

34 6. Discussion

6.1 Regional and local scale – similarities and differences Spatial variability is a function of scale. It is a well established argument that changes in scale change the relevant parameters for the spatial variability (e.g. Meentemeyer and Box, 1987; Walsh et al., 1998; Phillips, 1999). This has been clearly shown in this thesis, where parameters, such as vegetation, soil moisture and slope angle are important on both a regional and local scale, whereas a parameter such as elevation/permafrost is only important on a regional scale. Even though environmental parameters may be important on both scales, the nature of their influence may vary. On a regional scale the parameters operate more as thresholds values. In the regional grid-based model of solifluction occurrence only slope angles between 3 to 35° and areas above the treeline were considered (paper V). In the outcome of the study it is shown that high NDVI values are associated with solifluction occurrence. High NDVI values above the tree line are found in the valleys and on the south- and west-facing slopes of Mt Njulla and correspond to the vegetation types meadow with low herbs, grass heath, dry and fresh heath. Low NDVI values, where very few solifluction landforms occur, correspond to blocky areas with rocky outcrops, extreme snow beds and glaciers. Potential incoming short wave radiation (PR) was also identified as an important factor, where relatively low PR values correspond to areas where solifluction occur. Low PR values are found in valleys as compared to the summit areas, but the lowest absolute values are found on steep slopes and bedrock walls. On a local scale different vegetation types influence the solifluction movement rates. This is also true for the slope angle, but the local topography is not always important (paper VI). Meentemeyer (1989) proposes a number of factors that affect our choice of scale. This can be available data or mathematical and statistical considerations or dominant paradigm. In the end it seems that scales are uncons- ciously selected and arbitrary. In this thesis the two scale perspectives, local and regional were a clear focus from the beginning, but the scale of measurements (e.g. sampling interval) within these two scales was based on either statistical considerations or based on theoretical knowledge. Neverthe- less, a pilot study would always be required in order to detect the suitable spatial sampling interval. In the compilation study (paper IV) it became clear

35 that arbitrary choices of scale may be common, but it might also reflect the lack of details in the papers used in the study. The scale at which data is collected might be different than the scale at which the predictions are needed, creating a need for a change of scale from the measurements to the predictive model (Western and Blöschl, 1999). This was obvious in the compilation study (paper IV), but may also be problematic when DEM- derived parameters are used (paper II, IV and V). The resolution of the DEM will then dictate the resolution of the study or, if not, there may be a discre- pancy in the resolution of the dependent and the independent parameters. The use of a 50 m DEM in the regional studies (paper II and V) should however be a suitable resolution. Also, traditional methods suitable for slope scale measurements may not be suitable for measurements on a landscape scale, or might even be impossible to use.

6.2 Comparisons between the different methods The methods used in this thesis can be divided into field measurements, statistical analysis and GIS- and remote sensing-based analysis. The field measurements are in many ways the core of the analysis, but statistics and GIS analysis are needed in order to structure and interpret the field measurements. Statistical models present the risk of oversimplifying complex natural phenomena and move the attention away from the understanding of underly- ing causes of processes. The introduction of GWR allows to identify spatially varying relationships and thus to capture important variations which oth- erwise might not appear in global models. Equally, remote sensing does not offer the level of details that can be observed in the field, but does on the other hand offer both a spatial and temporal scale of study which is not possible to obtain in the field. The use of GIS also presents the possibility to easily visualize the regionalization of movement rates and to calculate geomorphic work for larger areas, but again the strength of the statistical relationships used for achieving this must be considered when interpreting the result. Recurrent problems in the models in the papers presented in this thesis are the rather low values of model fit (paper II, V and VI). Is this due to lack of suitable parameters or is it because it is very difficult to separate the interaction of naturally varying environmental and climatic parameters into dis- tinctly separated variables? We cannot explain the variations in the landscape without simplifying it and therefore there is also a need for models with a limited number of comprehensible parameters. In this context we need to consider what we want to use the models for. Today, much solifluction research is placed within a climate change context. What is a useful model in periglacial research in this context and how accurate does it have to be? As statistical modelling is a new emerging field in periglacial research,

36 models will generally require further development to become more reliable. Regarding what might be useful models, the development of process models may enhance our ability to understand and predict changes in periglacial dynamics due to a changing climate. Movement rates are assessed through aerial photo analysis (lobe front displacement) (paper III) and through field measurements (displacement of various parts of the lobes and adjacent ground) (paper V and VI). No “clas- sical” measurements focusing on a single lobe have been considered and equal attention has been given to activity outside the landforms. The grid measurements broaden the view on solifluction as not only a process produc- ing clearly distinguishable landforms, which has also been suggested by Berthling et al. (2002). An advantage of this strategy is that i) the values obtained represent solifluction activity of the slope and not only the landform and ii) a truly random data set is obtained which is useful when using average numbers. But since the measurements are not dictated by the locations of landforms it might also induce a problem of how to consider and understand the measured values. This means that sometimes the measurements of a form are made in the back of the form and at other locations measurements are done at the front of the form. When using the photo analysis method it is on the other hand clear that lobe fronts are measured.

6.3 Knowledge and methods Large systems are not replicable, as laboratory and most engineered systems are, nor are their constitution, composition, and structure designed or con- trolled (Haff, 1996). Two landscapes may be similar in many respects, but will always have distinctive characters. These can often be averaged away in small uniform systems, but in large systems they will persist (e.g. resistant soil layers, patterns of vegetation) and may significantly influence the course of geomorphic evolution (Haff, 1996). Part of what Haff (1996) brings up is also something that came to my mind at several occasions when working in the field. We work in environments that are constantly changing both spatially and temporally. A lobe is never a “perfect” lobe and even if we have set up clear criteria and definitions for measurements our eyes will be the judge in the end. When working with other people in the field this becomes obvious, we do not always make the same judgments. And since we do not work with an exact science we sometimes have to make arbitrary choices. This can for example be the lack of sharp boundaries of landforms and visual estimations of the presence or absence of vegetation. In this sense we can ask ourselves how repeatable a study actually is. We can never make exactly the same study, not even if it is done in the same location, probably not even if the same person does it. How much does this affect the results? Probably the change in result is most often not significant enough to change the con-

37 clusions of a study, but there may be a few cases where conclusions might diverge and this issue would be interesting to investigate further. Solifluction studies (and related processes) have either focused on process studies based on a large amount of empirical data obtained in the field (e.g. Harris, 1972, 2008b; Rapp and Åkerman, 1993; Jaeshe et al., 2003; Matsuo- ka et al., 2005; Beylich, 2008) or on modelling studies based on a limited number of field data, but with large amounts of digitally derived data (e.g. DEM) (e.g. Luoto and Seppäla, 2002; Hjort et al., 2007). In this sense, permafrost modelling is in advance, where the two perspectives more commonly are applied in conjunction (e.g. Lewkowicz and Ednie, 2004; Heggem et al., 2005). Modelling is however an emerging area within this field of periglacial research and the next step is to combine it with process studies. A wide range of methods is desirable in order to look at processes from different perspectives to possibly obtain a deeper understanding, but this only works if the methods are used in conjunction or that researchers work in a team. Phillips (1999) argues that processes or environmental factors, which operate or vary at fundamentally different scales, are independent of each other. Links between different representations are necessary to understand physical geography. Also Phillips (1999) means that different methodologies are appropriate or necessary at different scales. DEM:s are typically used for regional scale studies, but in paper VI local scale digital terrain models were created. Certainly there are methods which are difficult to apply at certain scale, such as devices for continuous measurements of solifluction movement rates at a regional scale.

6.4 Future outlook Few studies in geography have combined macrospatial and microspatial levels of analysis because of the large amount of data needed (Meentemeyer, 1989). Using remote sensing and the techniques provided in a GIS this should not be a problem today. This thesis is a first attempt to combine studies on solifluction on different scales and an attempt to move beyond the plot scale process studies. The different papers in the thesis have presented both new methods of measuring solifluction and new results related to the understanding of the occurrence of solifluction landforms and variations of movement rates in the Abisko region. New questions have also emerged. Questions to address:

1. More critical GIS and statistical analysis: What is the significance on the result when resolution and/or interpolation methods are changed? What is the significance of not removing spatial dependencies and not identi- fying spatially varying relationships between independent and dependent parameters?

38 2. Modelling can be combined with empirical process studies in order to better understand the processes and the capacity for upscaling for regional assessments. 3. How can we use the aerial photo analysis method to understand evolution of solifluction lobe morphometry (and as a further step, solifluction processes, if possible)? At what time scale is this type of analysis most relevant and at what time scale can changes in morphometry be reliably detected? 4. The new methods presented in this thesis need to be tested further in new and different regions (regionalization of movement rates, application of GWR, photo analysis, digital reconstruction of terrain at a local scale). 5. Empirical validation of the permafrost model.

39 7. Conclusions

This thesis has shown that there are variations in environmental controls on solifluction parameters in the Abisko region, northern Sweden that vary with the scale of measurement. On a regional scale the most important controls, vegetation, elevation and soil moisture has a function of essential require- ments (certain vegetation types and soil moisture availability) or thresholds values (elevation, slope angle). Morphometry also varies on a regional scale with smaller forms at higher altitude, while larger dimensions associated with a higher percentage of fine material and a high content of soil moisture. Dimensions of turf-banked lobes and terraces also decrease from west to east. The regionalization of sediment movement rates has allowed an assessment of the influence of solifluction on a landscape scale. The method of terrain classification for achieving this has a tendency to overestimate the areas of activity. Using the relationship between the probability of solifluction occurrence and the field-measured movement rates provides a result more close to the distribution of the originally mapped forms. The result of this method shows the highest movement rates on the east-facing slopes of Kärkevagge and on the east-facing slope of Njulla. The geomorphic work is equally largest on the east-facing slope of Kärkevagge, but decrease towards the east of the region and is smallest on the east-facing slope of Gohpascor- ru. It can therefore be concluded that solifluction is a more important denudational agent in the western part of the region than in the eastern part. Gen- erally, the calculated geomorphic work suggests that solifluction is a significant denudational agent in the region. However, movement rates are not very high, except for Kärkevagge, and depth of movement is rather shallow, which contributes to it being less important than previously estimated. For the temporal analysis of variations in solifluction activity it was shown that MAAT was positively correlated to movement rates in Kärke- vagge, but the cause-effect relationship is uncertain. This uncertainty is related to the limitations in establishing general relationships between variations in solifluction movement rates and variations in climate-based parameters on data from many different sources and over a long time, which was highlighted in the compilation study (paper IV). New methodologies of analyzing variations in solifluction activity and understanding local variation have also been tested. This includes the use of aerial photography for assessing catchment scale decadal solifluction activity

40 by lobe front advance has shown to be a time and cost effective method. Using this method, lobe front displacement can be quantified provided that the rate of movement has been sufficient between the two time intervals. This method also provides a possibility to understand solifluction behavior at new temporal and spatial scales. For the local variation of solifluction activity and the understanding of how environmental parameters interact with solifluction processes on a local scale, traditional field methods in combination with a surveying technique and GIS integration of data, together with statistical analysis, has been used. This method has a potential to provide better understanding of how these processes interact, but should be developed further and preferably include more measured parameters. The prelimi- nary results show that the influence of different environmental factors on variations in movement rates is site specific. These factors include soil moisture, vegetation type and slope angle. The fraction of fine material in the soil seems to be of minor importance on a local scale in influencing variations in movement rates. For the permafrost assessment it was concluded that about 30% of the in- vestigated region is underlain by discontinuous permafrost and elevation is the main controlling factor. Lower limits of widespread discontinuous permafrost decrease from c.1000 m a.s.l. in the west to c.800 m a.s.l. in the east. Geographically Weighted Regression was successfully applied as a statistical method of analyzing spatially varying relationships and is recommended to be applied further as an exploratory tool in modelling of periglacial processes.

42 Acknowledgements

For financial support of field work I want to thank the Swedish Society for Geography and Anthropology (Svenska Sällskapet för Antropologi och Geografi), who have made my field work possible. I also want to thank Geografiska föreningen in Uppsala, Gertrud Thelins minnesfond, Lilje- walchs minnesfond, the Swedish Society for Tourism (Svenska Turistföre- ningen) and Stiftelsen Ymer-80 for additional financial support. This money has allowed me to extend my field work, to make two visits to the Oslo Uni- versity and buy important field instrumentation. But money is definitely not all. My field work would not have been possible without field assistants. Here, Petter Bergeå has made a very important contribution in giving a support, which extends from a lot of patience and encouraging on rainy or long days surveying with the total station to contributing with very creative technical solutions to various problems that may occur in the field. Field work also includes long walks, breaks and evenings in huts and I am really grateful that Petter has been willing to and gladly shared this time with me. Field work is sometimes boring, but can also be very fun, especially if Amelie Larsson is part of the team. I have never laughed as much in the field as during the days we spend in Abisko together. You always manage to find a funny twist on everything. And you argued very well against the complexity of research (read collecting data in the field). Petter and Amelie thank you for everything! I also had a very nice time in the field with Kajsa Bovin, Börje Dahrén, and Axel Andersson, thank you a lot for your help. Time pass quickly and many years ago I also got valuable help from Dan Hörnell and Sofie Fre- driksson. During 2008 I brought my parents with me in the field, thank you mom and dad. You did a very good job digging and writing. And without your help of babysitting (babywalking) during the last months of writing I would never have been able to finish this. And Sally, without you I would not have had such a pleasant time finishing my thesis! Your wonderful ap- pearance makes every day a happy moment. Last but not least, who is more to thank? As a PhD-student you hear many stories about horrible supervisors. I have never had the opportunity to tell any of these stories about my supervisors, Jan Boelhouwers and Bernd Et- zelmüller. You are great! Thank you for all the time you have taken in providing lots of valuable comments on manuscripts and for always being available. Bernd, thank you for letting me come over to Oslo and spend some

43 valuable time there. And Jan, I am really grateful for all the nice discussions we have had and especially I am glad that you have such an open mind, which is not that common as one would expect within the scientific commu- nity. Not only supervisors are of great importance, but also other senior researchers, who can share their knowledge and experience. Here I am most grateful to Else Kolstrup, whose door has always been open. As a female senior researcher within a male dominated field you have been a great source of inspiration and motivation.

44 Sammanfattning

I den här avhandlingen presenteras en analys av variationen av jordflytning i Abiskoregionen i norra Sverige. Jordflytning, som även kallas solifluktion, definieras som en långsam flytrörelse av vattenmättad jord och är utbrett i alla områden där det finns markfrost. Jordflytningsprocesser, deras rörelse- hastigheter och resulterande landformer varierar dock mycket beroende på olika klimatrelaterade faktorer, såsom markfuktighetsförhållandena och anta- let frostcykler. Djupet på vilket islinser bildas och storleken av sådana, samt topografin är också viktiga faktorer. I ett större perspektiv kan förändringar i klimatet komma att påverka utbredningen och hastigheten av jordflytnings- rörelser, vilket i sin tur kan leda till förändringar av stabiliteten i det ytliga marktäcket. Många generella samband mellan jordflytning och miljö- och klimatparametrar har påvisats, men utvecklingen av en kvantitativ modellering av jordflytning är föga utvecklad. Syftet med denna avhandling är att kartlägga och analysera utbredningen och variationen av förekomst och rörelsehastigheter av jordflytning och att förklara vilka miljö- och klimatfaktorer som påverkar jordflytning i Abisko- regionen. Ett antal nya metoder har introducerats vilka möjliggör en ny typ av analys av den rumsliga variationen av jordflytning, såväl som av variationen över tid. Detta utförs genom att kombinera fältmätningar med geografiska informationssystem (GIS), fjärranalys och statistiska metoder. Resultaten presenteras i sex artiklar, som i tur och ordning fokuserar på morfometrin hos jordflytningsformer (artikel I), förekomsten av permafrost (artikel 2), analys av den rumsliga och temporala variationen av rörelsehastigheter hos jordflytningsformernas fronter med hjälp av flygfotografier (artikel III), temporala variationer av rörelsehastigheter (artikel III, IV), regionala och lokala rumsliga variationer av rörelsehastigheter (artikel III till VI) samt statistisk modellering av förekomsten av jordflytningsformer och beräkning av “geomorfiskt effekt” (geomorphic work), som är ett mått på erosion (artikel V och VI). Inom ramen för denna avhandling har ett tiotal lokaler valts ut i regionen mellan Abisko och Kärkevagge. Dessa lokaler reflekterar skillnader i bland annat topografi och nederbördsförhållanden. I Kärkevagge i väst är neder- börden nästan tre gånger så stor som i Abisko längre österut. Detta påverkar markfuktighetsinnehållet och mängden snö som smälter under våren. På de utvalda lokalerna har mätningar av rörelsehastigheten vid markytan genom- förts under perioden 2004 till 2008. Mätningarna har utförts genom att föra

45 ned träpinnar i marken utplacerade i ett rutnät. Lokalerna täcker såväl jordflytningsformer som mark utan jordflytning och variationer i topografi. Det- ta är viktigt för att kunna avgöra varför det sker jordflytning på vissa ställen, men inte på andra. Rutnäten varierar i storlek från 20×30 m till 50×100 m, beroende på hur stora variationerna i landskapet är. Sju av de utvalda lokalerna har också mätts in med hjälp av en totalstation och mätpunkterna har använts för att återskapa digitala modeller av terräng- en. Med hjälp av dessa modeller har relationerna mellan jordflytningsformernas rörelsehastigheter och miljöparametrar på en lokal skala analyserats. På regional skala har en rasterbaserad modell över förekomsten av jordflytningsformer tagits fram. Två aktivitetskartor över variationen i rörelsehas- tigheter i regionen har skapats. Den ena baserad på de i fält uppmätta rörel- sehastigheterna i kombination med en terrängklassificering. Den andra ut- ifrån sambandet mellan sannolikheten för förekomst av jordflytningsformer och röreselhastigheterna. För att mäta förändringar i jordflytningsformernas morfometri under perioden 1959 till 2000 och över ett större område än vad som kan täckas in genom fältmätningar, har flygbilder använts. Detta är en helt ny metod som gör det möjligt att se hur lobfronterna förändras över flera decennier. Där- med kan också slutsatser dras om lobfronternas rörelsehastigheter. Vidare har alla rörelsehastighetsmätningar som gjorts från 1950-talet och framåt på jordflytningsformer i Abiskoregionen analyserats i en gemensam studie. Även morfometrin på landformerna i regionen har uppmätts i fält och analyserats i relation till olika parametrar, såsom andelen finmaterial i jorden, markfuktighet, sluttningsvinkel och höjd över havet . Slutligen har också permafrostförekomsten i regionen kartlagts. Perma- frostförekomst kan inverka på jordflytningsprocesserna och är av betydelse för tolkningen av vilka mekanismer som dominerar i ett område. För att här- leda förekomsten av permafrost har BTS (bottom temperature of winter snow) -metoden använts. Mätningarna genomförs med hjälp av en stång och en termistor som trycks ned genom snötäcket där temperaturen vid markytan mäts. Resultaten visar att på en regional skala är vegetation, höjd över havet och markfuktighet viktiga faktorer för att förklara förekomsten av jordflytningsformer. Höjd över havet och markfuktighet (wetness index) är betydande faktorer för att förklara rörelsehastigheter. Rörelsehastigheterna är generellt sett högre i den västra delen av regionen. Resultaten antyder att hastigheter- na i denna del kan öka med ökande årsmedeltemperatur i luften. Även “ge- omorfisk effekt” är störst i västra delen av regionen. Vilka faktorer som är betydelsefulla för att förklara variationer i rörelse- hastigheter på lokal skala varierar mellan de olika lokalerna, men inkluderar vegetation, sluttningsgradient och markfuktighet. Flygfotoanalysen visar att de årliga rörelsehastigheterna av jordflytningsformernas lobfronter i Kärke-

46 vagge och Låktatjåkka mellan åren 1959 och 2000 varierar från icke mätbara till 63 mm per år. Permafrostmodellen visar att en sannolikhet större än 0.8 för förekomst av permafrost föreligger från cirka 1300 meter över havet i den västra delen av regionen, medan gränsen är lägre, ned till cirka 850 meter över havet, i den östra delen av regionen. Slutsatser som kan dras av denna avhandling är att de faktorer som kon- trollerar och påverkar jordflytning i Abiskoregionen varierar beroende på vilka skala som mätningarna avser. På regional skala fungerar de kontrolle- rande faktorerna som nödvändiga tröskelvärden för förekomsten av jordflytningsformer. Jordflytningsformernas morfometri varierar också på regional skala; mindre former återfinns i toppmiljöer på högre höjd över havet, medan större former återfinns i dalgångar på lägre höjd över havet. De största formerna finns i västra delen av regionen och där andel finmaterial i jorden och markfuktigheten är större. Genom att skapa en aktivitetskarta över rörel- sehastigheterna för hela regionen, kan man avgöra hur stor påverkan jordflytning har på landskapet på regional skala. Av denna studie framgår att sådan påverkan är av betydelse, dock mindre betydelse än vad som tidigare föreslagits. Angående den lokala variationen av rörelsehastigheter och förståelsen för hur olika faktorer påverkar jordflytning, visar denna studie att återskapande av lokala rumsliga modeller i GIS är en potentiellt användbar metod. Meto- den behöver dock utvecklas mer och inkludera fler relevanta parametrar än vad som används i denna studie. Fotoanalysen möjliggör att kvantifiera lob- fronters rörelsehastigheter på en tidsskala över flera decennier och att mäta ett stort antal jordflytningsformer, vilket tidigare varit mycket svårt att åstadkomma med traditionella metoder. Detta bidrar till att öka förståelsen av jordflytning på både en ny tids- och en ny rumslig skala.

47 References

Åkerman J., 1996, Slow mass movement and climatic relationships. In Advances in Hillslope Processes, vol. 2, Anderson MG, Brooks SM. (eds.); 1219-1256.

Åkerman J., 2005, Impacts of a warming sub-arctic on permafrost distribution in northern Sweden. Abstracts: Nordic Geography Meeting, Lund, Sweden, 11–15 May2005.Available: http://www.ngm.cc/html/abstracts/abstract_akerman_johansson.pdf [1 May 2006].

Andersson JG., 1906, Solifluction, a component of subaerial denudation. Journal of Geology, 14, 91-112.

Andersson L., Rafstedt T, von Sydow U., 1985, Fjällens vegetation, Norrbottens län. Swedish Environmental Protection Agency: Stockholm.

Atkinson J., Jiskoot H., Massari R., Murray T., 1998, Generalized linear modelling in geomorphology. Earth Surface Processes and Landforms, 23, 1185–1195.

Auzet A-V., Ambroise B., 1996, Soil creep dynamics, soil moisture and temperature conditions on forested slope in the granitic Vosges mountains, France. Earth Surface Processes and Landforms, 21, 531-542.

Ballantyne CK., 1986, Late Flandrian solifluction on the Fannich Mountains, Ross- shire. Scottish Journal of Geology, 22, 395-406.

Ballantyne CK., Harris C., 1994, The periglaciation of Great Britain, Cambridge University Press, Cambridge.

Benedict JB., 1970, Downslope soil movement in a Colorado alpine region: rates, processes and climatic significance. Arctic and Alpine Research, 2, 165-226.

Berthling I., Etzelmüller B., Kielland Larsen C., Nordahl K., 2002, Sediment fluxes from creep processes at Jomfrunut, southern Norway. Norsk Geografisk Tid- skrift, 56, 67-73.

Beskow G., 1935, Tjälbildningen och tjällyftning med särskild hänsyn till vägar och järnvägar, Sveriges geologiska undersökning. Serie C, Avhandlingar och upp- satser, 0082-0024; 375, Stockholm.

Beylich AA., 2008, Mass transfers, sediment budget and relief development in the Latnjavagge catchment, Arctic-oceanic Swedish Lapland. Zeitschrift für Geo- morphologie, Suppl. band 52, 149-197.

Bonnaventure PP., Lewkowicz AG., 2008, Mountain permafrost probability mapping using the BTS method in two climatically dissimilar locations, northwest Canada. Canadian Journal of Earth Sciences, 45, 443-455.

Brunsdon C. Fotheringham AS., Charlton ME., 1999, Some notes on parametric signficance tests for geographically weighted regression. Journal of Regional Science 39, 497-524.

Caine N., 1976, A uniform measure of subaerial erosion. Geological Society of America Bulletin, 87, 137-140.

Darmody RG., Thorn CE., Dixon JC., Schlyter P., 2000, Soils and landscapes of Kärkevagge, Swedish Lapland. Soil Science Society of America Journal, 64, 1455-1466.

Douglas TD., Harrison S., 1996, Turf-banked terraces in Öraefi, Southern Iceland: morphometry, rates of movement and environmental controls. Arctic and Alpine Research, 28, 228-236.

Embleton C., King C., 1975, Periglacial Geomorphology (2nd ed.), Edward Arnold, London. van Everdingen R (ed.), 1998 (revised May 2005), Multi-language glossary of permafrost and related ground-ice terms, National Snow and Ice Data Center for glaciology, Boulder, CO.

Fotheringham AS., Brunsdon C., Charlton ME., 2002, Geographically Weighted Regression: The Analysis of Spatially Varying Relationships. Wiley: Chichester.

French H., 1996, The periglacial environment, Addison Wesley Longman Limited, England.

French HM., 2007, The Periglacial Environment (3d edition). Wiley, Chichester, 458 pp.

Gamble DW., Meentemeyer, V., 1996, The role of scale in research on the Hima- laya-Ganges-Brahmaputra interaction. Mountain Research and Development, 16, 2, 149-155.

Gamper M., 1983, Controls and rates of movement of solifluction lobes in the eastern Swiss Alps. In Proceedings of the 4th International Conference on Perma- frost, 328-333.

Gamper M., 1987, Mikroklima und Solifluktion: Resultate von Messungen im schweizerischen Nationalpark in der Jahren 1975-1985. Göttinger Geogra- phische Abhandluneng, 84, 31-44.

Goodfellow BW., Stoeven AP., Hättetsrand C., Kleman J., Jansson KN., 2008, De- ciphering a non-glacial/glacial landscape mosaic in the northern Swedish mountains. Geomorphology, 93, 213-232.

49 Gruber S., Hoelzle M., 2001, Statistical modelling of mountain permafrost distribution: Local calibration and incorporation of remotely sensed data. Permafrost and Periglacial processes, 12, 69-77.

Haeberli W., 1996, On the morphodynamics of ice/debris-transport systems in cold mountain areas. Norsk Geografisk Tidskrift, 50, 3-9.

Haeberli W., 1973, Die basis temperature der winterlichen schneedecke als möglich- er indikator für die verbreitung von permafrost. Zeitschrift für Gletscherkunde und Glazialgeologie 9, 221-227.

Haff PK., 1996, Limitations on predictive modelling in Geomorphology, in Rhoads B.L., Thorn C.E (eds.), The Scientific Nature of Geomorphology, John Wiley & Sons, Chichester, England.

Harris C., 1972, Processes of soil movement in turf-banked solifluction lobes, Oks- tindan, northern Norway, in Price R.J, Sugden D.E. (eds.). Polar Geomorpholo- gy, Institute of British Geographers, Special Publication, 4, 155-174.

Harris C., 1977, Engineering properties, groundwater conditions, and the nature of soil movement on a solifluction slope in north Norway. Quarterly Journal of Engineering Geology, 10, 27-43.

Harris C., 1993, The role of climatic and soil properties in periglacial solifluction: Evidence from laboratory simulation experiments, in Frenzel, B. (ed.), Solifluc- tion and climatic variations in the Holocene, special issue: ESF Project “Euro- pean Paleoclimate and Man”, 6, European Science Foundation, Strasbourg.

Harris C., Davies MCR., Coutard J-P., 1995, Laboratory simulations of periglacial solifluction: significance of porewater pressures, moisture contents and un- drained shear strength during soil thawing. Permafrost and Periglacial Processes, 7, 293-312.

Harris C., Davies MCR., Coutard J-P., 1997, Rates and processes of periglacial solifluction: An experimental approach. Earth Surface Processes and Land- forms, 22, 849-868.

Harris C., Davies MCR., Rea BR., 2003, Gelifluction: viscous flow or plastic creep? Earth Surface Processes and Landforms, 28, 1289-1301.

Harris C., Kern-Leutschg M., Murton J., Font M., Davies M., Smith F., 2008a, Solif- luction processes on permafrost and non-permafrost slopes: Results of a large- scale laboratory simulation. Permafrost and Periglacial Processes, 19, 359-378.

Harris C., Kern-Luetschg M., Smith F., Isaksen K., 2008b, Solifluction processes in an area of seasonal ground freezing, Dovrefjell, Norway. Permafrost and Perig- lacial Processes, 19, 31-47.

Heggem E., Juliussen H., Etzelmüller B., 2005, Mountain permafrost in Central- Eastern Norway. Norsk Geografisk Tidskrift, 59, 94-108.

50 Hjort J., Luoto M., Seppäla M., 2007, Landscape scale determinant of periglacial features in subarctic Finland: A grid-based modelling approach. Permafrost and Periglacial Processes, 18, 115-127.

Hoelzle M., 1992, Permafrost occurence from BTS measurements and climatic parameters in the eastern Swiss Alps. Permafrost and Periglacial Processes, 3, 143-147.

Holness SD., 2001, Periglacial slope processes, landforms and environment at Ma- rion Island, maritime Subantarctic, PhD thesis, University of the Western Cape.

Holness SD., 2004, Sediment movement rates and processes on cinder cones in the maritime subantarctic (Marion Island). Earth Surface Processes and Landforms, 29, 91-103.

Hugenholtz C., Lewkowicz A., 2002, Morphometry and environmental characteristics of turf-banked solifluction lobes, Kluane Range, Yukon Territory, Canada. Permafrost and Periglacial Processes, 13, 301-313.

Isaksen K., Hauck C., Gudevang E., Odegård R., Sollid J., 2002, Mountain permafrost distribution in Dovrefjell and Jotunheimen, sourthern Norway, based on BTS and DC resistivity tomography. Norsk Geografisk Tidskrift, 56, 122-136.

Jaesche P., Veit H., Huwe B., 2003, Snow cover and soil moisture controls on solifluction in an arean of seasonal frost, eastern Alps. Permafrost and Periglacial Processes, 14, 399-410.

Jensen JR., 1996, Issues involving the creation of digital elevation models and terrain corrected orthoimagery using soft-copy photogrammetry. In Digital Photo- grammtery : An Addendum to the Manual Photogrammetry, Greve C (ed.). American Society for Photogrammetry and Remote Sensing: Bethesda, MD; 167-179.

Josefsson M., 1990, Ground temperature variations in a sub-arctic mountain valley, Abisko, Northern Sweden. Geografiska Annaler, 72, 179-190.

Kane DL., 1997, The impact of hydrologic perturbations on arctic ecosystems in- duced by climate change, in Oechel W.C., Callaghan T., Gilmanov T., Holten J.I., Maxwell B., Molau U., and Sveinbjörnsson B., (eds), Global Change and Arctic Terrestrial Ecosystems, Springer, New York, 63–81.

Kinnard C., Lewkowicz AG., 2005, Movement, moisture and thermal conditions at a turf-banked solifluction lobe, Kluane Range, Yukon Territory, Canada. Perma- frost and Periglacial Procesees, 16, 261-175.

Kinnard C., Lewkowicz AG., 2006, Frontal advance of turf-banked solifluction lobes, Kluane Range, Yukon Territory, Canada. Geomorphology, 3-4, 261-276.

Kleman J., Stroeven AP., 1997, Preglacial surface remnats and Quaternary glacial regimes in northwestern Sweden. Geomophology, 19, 35-54.

51 Kulling O., 1964, Översikt over norra Norrbottensfjällens Kaledonberggrund. Sve- riges Geologiska Undersökning, serie Ba översiktskartning med beskrivningar, 19, 166.

Lane S., Richards K., Chandler J., 1998, Landform monitoring, modelling and analysis, John Wiley and Sons, Chichester.

Lewkowicz A., Ednie M., 2004, Probability mapping of mountain permafrost using the BTS method, Wolf Creek, Yukon territory, Canada. Permafrost and Perig- lacial Processes. 15, 67-80.

Liston GE., McFadden JP., Sturm M., Pielke RA., 2002, Modelled changes in arctic tundra snow, energy and moisture fluxes due to increased shrubs. Global Change Biology, 8, 17–32.

Luoto M., Seppälä M., 2002, Modelling the distribution of palsas in Finnish Lapland with logistic regression and GIS. Permafrost and Periglacial Processes, 13, 17– 28.

Matsuoka N., 2001, Solifluction rates, processes and landforms: a global review. Earth-Science Reviews, 55, 107-134.

Matsuoka N., Ikeda A., Date T., 2005, Morphometric analysis of solifluction lobes and rock glaciers in the Swiss Alps. Permafrost and Periglacial Processes, 16, 99-113.

Matsuoka N., 2006, Monitoring periglacial processes: Towards construction of a global network. Geomorphology, 80, 20-31.

Matthews JA., Ballantyne CK., Harris C., McCarroll D., 1993, Solifluction and climatic variations in the Holocene: Discussion and synthesis. In Solifluction and climatic variations in the Holocene, special issue: ESF Project “European Paleoclimate and Man, Frenzel B (ed.). European Science Foundation: Stras- bourg: 339-361.

Meentemeyer V., Box E., 1987, Scale effects in landscape studies, in Turner M.G.(ed), Landscape heterogeneity and disturbance. Springer Verlag, New York, 15-36.

Meentemeyer V., 1989, Geographical perspectives of space, time and scale. Land- scape ecology, 3, 163-173.

Nelson FE., Outcalt SI., 1987, A computational method for prediction and regionalization of permafrost. Arctic and Alpine Research, 19, 279-288.

Nyberg R., 1991, Geomorphic processes at snowpatch sites in the Abisko Moun- tains, northern Sweden. Zeitschrift für Geomorphologie, 35, 321-343.

Nyberg R., 1993, Freeze-thaw activity and some of its geomorphic implications in the Abisko Mountains, Swedish Lappland, Permafrost and Periglacial Processes, 4, 37-47.

52 Perez FL., 1988, The movement of debris on a high Andean talus. Zeitschrift für Geomorpholgie, 32, 77-99.

Phillips JD., 1999, Methodology, scale and the field of dreams. Annals of the Asso- ciation of American Geographers, 89, 754-760.

Pissart A., 1993, Understanding the controls on solifluction movements in different environments: a methodology and its application in the French Alps. In Solifluc- tion and climatic variations in the Holocene, special issue: ESF Project “Euro- pean Paleoclimate and Man, Frenzel B (ed.). European Science Foundation: Strasbourg: 209-216.

Price LW., 1973, Rates of mass wasting in the Ruby range, Yukon Territory. North American Contribution, 2nd International Conference ion Permafrost, Yakutsk, National Academy Press: Washington; 235-245.

Price LW., 1990, Subsurface movement on solifluction slopes in the Ruby Range, Yukon Territory, Canada: a 20-year study. Arctic and Alpine Research, 23, 200– 205.

Rapp A., 1960, Recent development of mountain slopes in Kärkevagge and sur- roundings, northern Scandinavia. Geografiska Annaler, 42, 71-200.

Rapp A., Strömquist L., 1979, Field experiments on mass movements in the Scandi- navian Mountains with special reference to Kärkevagge, Swedish Lappland, Meddelanden från Uppsala universitets geografiska institution, series A, 288.

Rapp A., Åkerman J., 1993, Slope processes and climate in the Abisko mountains, northern Sweden. In Solifluction and climatic variations in the Holocene, special issue: ESF Project “European Paleoclimate and Man, Frenzel B (ed.). Euro- pean Science Foundation: Strasbourg: 163-177.

Ridefelt H., Boelhouwers J., 2006, Observations on regional variations in solifluction landform morphology and environment in the Abisko region, northern Sweden. Permafrost and Periglacial Processes, 17, 253-266.

Ridefelt H., Etzelmüller B, Boelhouwers J, Jonasson C., 2008, Mountain permafrost distribution in the Abisko region, sub-Arctic northern Sweden. Norsk Geograf- isk Tidskrift, 62, 278-289.

Ridefelt H., Åkerman J., Beylich AA., Boelhouwers J., Kolstrup E., Nyberg R., in press, 56 years of soliflcution measurements in the Abisko Mountains, northern Sweden – perspectives of slow soil surface movement and long-term monitoring, Geografiska Annaler.

Rodhe L., Pyykonen M., Krekula M., 1999, Soil map Abisko (digitized working material).

Rudberg S., 1958, Some observations concerning mass movements on slopes in Sweden. Geologiska Föreningen i Stockholm Förhandlingar, 80, 114-125

53 Rudberg S., 1960, Recent quantative work on slope processes in Scandinavia. Zeit- schrift für Geomorphologie, Suppl. band 9, 44-56.

Rudberg S., 1962, A report on some field observations concerning periglacial geomorphology and mass movement on slopes in Sweden. Biuletyn Peryglacjalny, 11, 311–323.

Smith DJ., 1988 Rates and controls of soil movement on a soliflcution slope in the Mount Rae area, Canadian Rocky mountains. Zeitschrift für Geomorphologie, Suppl. band, 71, 25-44.

Smith DJ., 1987, Late Holocene solifluction lobe activity in the Mount Rae area, southern Canadian Rocky Mountains. Canadian Journal of Earth Sciences, 24, 1634-1642.

Smith DJ., 1992, Long-term Rates of Contemporary solifluction in the Canadian Rocky Mountains. In Periglacial geomorphology, Dixon JC, Abrahams AD (eds.); 201-221.

Taber S., 1930, The mechanisms of frost heaving. Journal of Geology, 38, 303-317.

Thorn C., 2003, Making the most of new instrumentation. Permafrost and periglacial processes, 14, 411-419.

Tricart J., 1969, Geomorphology of cold environments. Macmillan and Co Ltd, Lon- don.

Turner MG., O’Neill RV., Gardner RH., Milne BT., 1989, Effects of changing spatial scale on the analysis of landscape pattern. Landscape Ecology, 3, 153-162.

Walsh SJ., Bian L., McKnight S., Brown DG., Hammer ES., 2003, Solifluction steps and risers, Lwee Ridge, Glacier National Park, Montana, USA; a scale and pattern analysis. Geomorphology, 55, 381-398.

Washburn AL., 1979, Geocryology: A survey of periglacial processes and environments, London.

Washburn AL., 1967, Instrumental observations of mass-wasting in the Mesters Vig District, Norteast Greenland. Meddelelser om Grönland, 166, 1-297.

Western AW., Blöschl G., 1999, On the spatial scaling of soil moisture. Journal of Hydrology, 217, 203-224.

Williams PJ., 1957, Some investigations into solifluction features in Norway. Geo- graphical Journal, 123, 42-58.

Williams PJ., Smith MW., 1989, The frozen Earth, Cambridge University press, Cambridge.

Van Vliet-Lanoë B., 1998, Frost and soils: Implications for paleosols, paleoclimates and stratigraphy. Catena, 34, 157-183.

Van Vliet-Lanoë B., 1985, Frost effects in soils, in Boardman J. (ed.), Soils and Quaternary landscape evolution, John Wiley & Sons, Chichester, England.

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