Rolf Nyberg

Alpine Debris Flows in Northern Scandinavia: Morphology and dating by lichenometry

ABSTRACTThe effects of an extreme rainfall triggering debris flows (mudflows) in the mountains S of Abisko, N Sweden, in 1979, are evaluated with regard to geomorphological impact. Several older events of debris flows in the same area during postglacial time are evident in the morphology of the slopes. Where such flows have occurred repeatedly, debris accumulations superficially similar to alluvial cones and referred to as debris flow cones are built. An attempt at dating old flows by means of lichenometry indicated at least four earlier events within the last 2700 years in Nissunvagge. A map of the spatial pattern of known rainfall-triggered mass movements in northern Lappland is presented to support the hypothesis of geomorphic impact of extreme rainfall in three area size classes called regions, cells and spots.

Mass movements, nivation processes and climatic fluctuations in northern Scandinavian mountains

Climatic fluctuations during the twentieth century in northern Scandinavia and Spitsbergen may have influenced the frequency of rainfall-triggered mass movements such as debris flows, with a shorter recurrence interval during colder periods before c. 1920 and after c. 1960, and less frequent occurrence during the intervening warm period. However, precipitation data are contradictory regarding contrasts between warm and cold periods, and the recorded high number of debris flow events during later decades may also be a result of improved observations. Studies of nivation processes and snow cover distribution may provide additional information on climatic fluctuations. Examples are given of the use of nivation landforms as climatic indicators.

The rainstorm of August 1998 in the Abisko area, northern Sweden: preliminary report on observations of erosion and sediment transport.

The rainstorm of August 1998 in the Abisko area, northern Sweden: preliminary report on observations of erosion and sediment transport

Observations of slushflows and their geomorphological effects in the Swedish mountain area

Observations of slushflows and their geomorphological effects in the Swedish mountain area.

NIVATION AND LOCAL GLACIATION IN N. AND S. SWEDEN. A PROGRESS REPORT

An ongoing geomorphological research project on nivation and local glaciation is testing the following working ./ hypothesis. After the main Weichselian deglaciation in south Sweden, periods of cold tundra conditions returned, e.g. in the Younger Dryas period. Fossil ice-wedge casts and rocks with wind-polis- ^// hed facets and flute marks indicate permafrost climate and _ strong winds with snow-drifting from easterly and westerly direc- tions. Large masses of drifting snow were trapped in the canyon valleys of Soderasen and other horst ridges, where nivation / hollows and small glacial cirques were slightly rejuvenated. Ni- / veo-eolian sand was deposited in some hollows and also incorpo- // rated in some moraine-like deposits. The bedrock hollows and cirques were mainly excavated during the much longer tundra 64// periods before the advances of the Quaternary main ice sheets over Scania. But the hollows survived the erosional impact of the ice sheets. The work to test the hypothesis is making progress, by analysis/// of the Late-Glacial forms and material in south Sweden, by \ comparisons with landforms, material and processes in the actual , // mountain tundra of Abisko in the north, and by comparisons - /

Geomorphic features as indicators of climatic fluctuations in a periglacial environment, northern Sweden

Geomorphic features as indicators of climatic fluctuations in a periglacial environment, northern Sweden

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

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