University of Lapland

About: University of Lapland is a education organization based out in Rovaniemi, Finland. It is known for research contribution in the topics: Arctic & Context (language use). The organization has 665 authors who have published 1870 publications receiving 39129 citations. The organization is also known as: University of Rovaniemi & Lapin yliopisto.

Grazing decreases N partitioning among coexisting plant species

Abstract: 1. Herbivores play a key role in shaping ecosystem structure and functions by influencing plant and microbial community composition and nutrient cycling.2. This study investigated the long-term eff ...

Basal ice formation in snow cover in Northern Finland between 1948 and 2016

Abstract: Basal ice formation in the terrestrial snowcover is a commonphenomenon innorthern circumpolar areas, onehaving significant impacts on ecosystems, vegetation, animals andhuman activities. There is limited knowledge on the spatial and temporal occurrence of basal ice formationbecause of the sparse observationnetwork and challenges involved in detecting formation events.Wepresent a unique dataset on the annual extent of ice formation events in northernFinlandbetween 1948 and2016based on reindeer herders’descriptions of the cold season in theirmanagement reports. In extreme years, basal ice can formoverwide geographical extents. In approximately half of the herding districts studied, it occurredmore frequently in the period1983–2016 than in the period 1948–1982. Furthermore,five out of sevenof themost extensive basal ice formation events (90thpercentile)occurred between 1991 and 2016.Themost commonly reported processes related to ice formationwere thawor rain-on-snowevents followedby freezingof the snowcover. Yearswith extensive basal ice formationwere often characterized by above-averageOctober–December air temperatures, air temperature variations around0 °Cand relatively highprecipitation.However, basal ice did not occur during all warmandwet earlywinters, and formation eventswere generallyweakly linked to the large-scale atmospheric teleconnections.Another risk factor for reindeer grazing associatedwithwarmand rainy earlywinters is the growthofmycotoxinproducingmoldsbelow the snow.Approximately 24%of all reportedmold formation events co-occurred withbasal ice formation. The prevalence and frequency of basal ice formation events canbe assessed based onour results.Ourwork contributes to understanding long-termfluctuations and changes in snow and ice conditions and the impacts of this variability in circumpolar areas.

The role of lake size and local phenomena for monitoring ground-fast lake ice.

Abstract: In this study, we assess the effect of the lake size on the accuracy of a threshold-based classification of ground-fast and floating lake ice from Sentinel-1 Synthetic Aperture Radar (SAR) imagery. For that purpose, two new methods (flood-fill and watershed method) are introduced and the results between the three classification approaches are compared regarding different lake size classes for a study area covering most of the Yamal Peninsula in Western Siberia. The focus is on April, the stage of maximum lake ice thickness, for the years 2016 and 2017. The results indicate that the largest lakes are likely most prone to errors by the threshold classification. The newly introduced methods seem to improve classification results. The results also show differences in fractions of ground-fast lake ice between 2016 and 2017, which might reflect differences in temperatures between the winters with severe impact on wildlife and freshwater fish resources in the region. Patterns of low backscatter responsible for the classification errors in the centre of the lakes were investigated and compared to the optical Sentinel-2 imagery of late-winter. Strong similarities between some patterns in the optical and SAR data were identified. They might be zones of thin ice, but further research is required for clarification of this phenomenon and its causes.

Dendrochronological investigation of wood extractives

Abstract: X-ray microdensitometry was applied to a set of Scots pinewood (i.e. low extractive content). Earlywood and latewood properties were determined as minimum and maximum densities of each tree ring and the potential influence of acetone-soluble extractives (i.e. non-structural and secondary constituents of wood) was estimated using tree-ring statistics. The occurrence of extractives in different portions of wood was determined using dendrochronological methods, by comparing the densities of unextracted and extracted wood. It was not only found that unextracted samples exhibited inflated earlywood and latewood density values, but the growth trends were also altered. Extractives flattened the inter-annual growth variability, both in earlywood and latewood, and influenced the estimation of intra-annual radial growth variations. Characterizing the varying amount of extractives is of inter-disciplinary importance. The results in this study describe their occurrence and show that the radial variations in extractives could be highly detailed by simply using densitometry-based dendrochronology.

Influence of anisotropy on velocity and age distribution at Scharffenbergbotnen blue ice area

Abstract: We use a full-Stokes thermo-mechanically coupled ice-flow model to study the dynamics of the glacier inside Scharffenbergbotnen valley, Dronning Maud Land, Antarctica. The domain encompasses a high accumulation rate region and, downstream, a sublimation-dominated bare ice ablation area. The ablation ice area is notable for having old ice at its surface since the vertical velocity is upwards, and horizontal velocities are almost stagnant there. We compare the model simulation with field observations of velocities and the age distribution of the surface ice. No satisfactory match using an isotropic flow law could be found because of too high vertical velocities and much too high horizontal ones in simulations despite varying enhancement factor, geothermal heat flux and surface temperatures over large ranges. However, the existence of a pronounced ice fabric may explain the observed present-day surface velocity and mass balance distribution in the inner Scharffenbergbotnen blue ice area. Near absence of data on the temporal evolution of Scharffenbergbotnen since the Late Glacial Maximum necessitates exploration of the impact of anisotropy using prescribed ice fabrics: isotropic, single maximum, and linear variation with depth, in both two-dimensional and three-dimensional flow models. The realistic velocity field simulated with a noncollinear orthotropic flow law, however, produced surface ages in significant disagreement with the few reliable age measurements and suggests that the age field is not in a steady state and that the present distribution is a result of a flow reorganization at about 15 000 yr BP. In order to fully understand the surface age distribution, a transient simulation starting from the Late Glacial Maximum including the correct initial conditions for geometry, age, fabric and temperature distribution would be needed. This is the first time that the importance of anisotropy has been demonstrated in the ice dynamics of a blue ice area and demonstrates the need to understand ice flow in order to better interpret archives of ancient ice for paleoclimate research.