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  • 1. Abbott, Benjamin W.
    et al.
    Jones, Jeremy B.
    Schuur, Edward A. G.
    Chapin, F. Stuart
    Bowden, William B.
    Bret-Harte, M. Syndonia
    Epstein, Howard E.
    Flannigan, Michael D.
    Harms, Tamara K.
    Hollingsworth, Teresa N.
    Mack, Michelle C.
    McGuire, A. David
    Natali, Susan M.
    Rocha, Adrian V.
    Tank, Suzanne E.
    Turetsky, Merritt R.
    Vonk, Jorien E.
    Wickland, Kimberly P.
    Aiken, George R.
    Alexander, Heather D.
    Amon, Rainer M. W.
    Benscoter, Brian W.
    Bergeron, Yves
    Bishop, Kevin
    Blarquez, Olivier
    Bond-Lamberty, Ben
    Breen, Amy L.
    Buffam, Ishi
    Cai, Yihua
    Carcaillet, Christopher
    Carey, Sean K.
    Chen, Jing M.
    Chen, Han Y. H.
    Christensen, Torben R.
    Cooper, Lee W.
    Cornelissen, J. Hans C.
    de Groot, William J.
    DeLuca, Thomas H.
    Dorrepaal, Ellen
    Fetcher, Ned
    Finlay, Jacques C.
    Forbes, Bruce C.
    French, Nancy H. F.
    Gauthier, Sylvie
    Girardin, Martin P.
    Goetz, Scott J.
    Goldammer, Johann G.
    Gough, Laura
    Grogan, Paul
    Guo, Laodong
    Higuera, Philip E.
    Hinzman, Larry
    Hu, Feng Sheng
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jafarov, Elchin E.
    Jandt, Randi
    Johnstone, Jill F.
    Karlsson, Jan
    Kasischke, Eric S.
    Kattner, Gerhard
    Kelly, Ryan
    Keuper, Frida
    Kling, George W.
    Kortelainen, Pirkko
    Kouki, Jari
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Laudon, Hjalmar
    Laurion, Isabelle
    Macdonald, Robie W.
    Mann, Paul J.
    Martikainen, Pertti J.
    McClelland, James W.
    Molau, Ulf
    Oberbauer, Steven F.
    Olefeldt, David
    Pare, David
    Parisien, Marc-Andre
    Payette, Serge
    Peng, Changhui
    Pokrovsky, Oleg S.
    Rastetter, Edward B.
    Raymond, Peter A.
    Raynolds, Martha K.
    Rein, Guillermo
    Reynolds, James F.
    Robards, Martin
    Rogers, Brendan M.
    Schaedel, Christina
    Schaefer, Kevin
    Schmidt, Inger K.
    Shvidenko, Anatoly
    Sky, Jasper
    Spencer, Robert G. M.
    Starr, Gregory
    Striegl, Robert G.
    Teisserenc, Roman
    Tranvik, Lars J.
    Virtanen, Tarmo
    Welker, Jeffrey M.
    Zimov, Sergei
    Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment2016In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 11, no 3, 034014Article in journal (Refereed)
    Abstract [en]

    As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.

  • 2. Acharya, Kamal Prasad
    et al.
    De Frenne, Pieter
    Brunet, Jörg
    Chabrerie, Olivier
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Diekmann, Martin
    Hermy, Martin
    Kolb, Annette
    Lemke, Isgard
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Verheyen, Kris
    Graae, Bente Jessen
    Latitudinal variation of life-history traits of an exotic and a native impatiens species in Europe2017In: Acta Oecologica, ISSN 1146-609X, E-ISSN 1873-6238, Vol. 81, 40-47 p.Article in journal (Refereed)
    Abstract [en]

    Understanding the responses of invasive and native populations to environmental change is crucial for reliable predictions of invasions in the face of global change. While comparisons of responses across invasive species with different life histories have been performed before, comparing functional traits of congeneric native and invasive species may help to reveal driving factors associated with invasion. Here we compared morphological functional trait patterns of an invasive species (Impatiens parviflora) with its congeneric native species (I. noli-tangere) along an approximately 1600 km European latitudinal gradient from France (49 degrees 34'N) to Norway (63 degrees 40'N). Soil nitrogen was recorded during six weeks of the growing season, and light, soil moisture, and nutrient availability were estimated for each sampled population using community weighted means of indicator values for co-occurring species. Temperature data were gathered from nearby weather stations. Both the native and invasive species are taller at higher latitudes and this response is strongest in the invasive species. Seed mass and number of seeds per capsule increase in I. noli-tangere but decrease in I. parviflora towards higher latitudes. Surprisingly, plant height in the invasive I. parviflora decreases with increasing soil nitrogen availability. The latitudinal pattern in seed mass is positively related to temperature in I. noli-tangere and negatively in I. parviflora. Leaf area of both species decreases with increasing Ellenberg indicator values for nitrogen and light but increases with increasing soil moisture. Soil nitrogen concentrations and Ellenberg indicator values for nitrogen have significant positive (I. nolitangere) and negative (I. parviflora) effects on the number of seeds per capsule. Our results show that the native I. noli-tangere has efficient reproduction at its range edge while the invasive I. parviflora shows a marked decrease in seed size and seed number per capsule. These patterns are unrelated to the growth and obtained size of the plants: even low soil nitrogen availability in the north seemed not to limit plant growth and size. Our results suggest that the invasive I. parviflora tends to become more invasive at lower latitudes by producing heavier seeds and more seeds per capsule.

  • 3.
    Adriansson, Linus
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Stockholm i färger: En kritisk diskursanalys av kulturarvets produktion och legitimering i stadens bebyggelsemiljö2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Avsikten med denna uppsats är att med en kritisk diskursanalys undersöka hur kunskap om kulturarvet och kulturhistoriska värden konstrueras i Stockholms byggda miljö. Akademisk litteratur inom kulturarvsforskningen beskriver en situation där det uppstått ett glapp mellan teori och praktik inom kulturarvssektorn som vidgats sedan postmodernismens och konstruktionismens framväxt i början på 1970-talet. Den utövande kulturarvsvården och värderingsprocessen är i stor utsträckning styrd av värdeorienterade klassificeringssystem där utgångspunkten är att finna och tolka olika värdetyper i ett objekt. Detta traditionella förhållningssätt är en del av ”den auktoriserade kulturarvsdiskursen”; ett begrepp inom kulturarvsforskningen som menar att kulturarvssektorn premierar traditionella värden genom expertutpekanden vilket leder till en reproduktion av kanoniserade objekt med vissa ideologiska förtecken. Sedan år 1974 finns det i Sverige nationella kulturpolitiska mål fastslagna och sedan år 2012 finns det fyra nationella kulturmiljömål som landets kulturmiljövårdande institutioner ska sträva. Målens tankegods förmedlar en ambition om att göra kulturmiljöer och kunskap tillgängligt för att främja demokratisering av kulturarvet. I Stockholms kommun är det Stadsmuseet som ansvarar för utpekandet och klassificeringen av kulturhistoriskt värdefulla byggnader och miljöer. Syftet med undersökningen är att bidra med en djupare förståelse för hur kunskapen om kulturhistoriska värden i Stockholms byggda kulturmiljö produceras och legitimeras. Resultat och analys visar att diskurserna i Stadsmuseets översiktsdokument sedan klassificeringens introduktion under tidigt 1980-tal har förändrats av ideologiska, politiska och ekonomiska element. Museets och kommunens samtida översiktsdokument har en anknytning till kunskapsläget inom kulturarvsforskningen genom att argumentera för relativa, pluralistiska värden. Men den traditionella värdesynen och expertdiskursen i värderingsprocessen har lett till en värdering och klassificering som reproducerar en traditionell förståelse av det byggda kulturarvet. En universell metod i kombination med intern praxis används för att identifiera vilka kulturhistoriska värden som finns, utan att precisera vilka egenskaper som upprätthåller dessa värden. Det ger klassificeringen en svag anknytning till kulturarvsforskning, regeringens kulturpolitiska mål och den egna institutionens värdesyn i samtida översiktsdokument.

  • 4. Ahlkrona, Josefin
    et al.
    Lötstedt, Per
    Kirchner, Nina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zwinger, Thomas
    Dynamically coupling the non-linear Stokes equations with the shallow ice approximation in glaciology: Description and first applications of the ISCAL method2016In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 308, 1-19 p.Article in journal (Refereed)
    Abstract [en]

    We propose and implement a new method, called the Ice Sheet Coupled Approximation Levels (ISCAL) method, for simulation of ice sheet flow in large domains during long time-intervals. The method couples the full Stokes (FS) equations with the Shallow Ice Approximation (SIA). The part of the domain where SIA is applied is determined automatically and dynamically based on estimates of the modeling error. For a three dimensional model problem, ISCAL computes the solution substantially faster with a low reduction in accuracy compared to a monolithic FS. Furthermore, ISCAL is shown to be able to detect rapid dynamic changes in the flow. Three different error estimations are applied and compared. Finally, ISCAL is applied to the Greenland Ice Sheet on a quasi-uniform grid, proving ISCAL to be a potential valuable tool for the ice sheet modeling community.

  • 5. Ahlström, A. P.
    et al.
    Anderson, B.
    Arenillas, M.
    Bajracharya, S.
    Baroni, C.
    Bidlake, W. R.
    Braun, L. N.
    Caceres, B.
    Casassa, G.
    Ceballos, J. L.
    Cobos, G.
    Davila, L. R.
    Delgado Granados, H.
    Demberel, O.
    Demuth, M. N.
    Espizua, L.
    Fischer, A.
    Fujita, K.
    Gadek, B.
    Ghazanfar, A.
    Hagen, J. O.
    Hoelzle, M.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Karimi, N.
    Li, Z.
    Martinez De Pison, E.
    Pelto, M.
    Pitte, P.
    Popovnin, V. V.
    Portocarrero, C. A.
    Prinz, R.
    Ramirez, J.
    Rudell, A.
    Sangewar, C.
    Severskiy, I
    Sigurdsson, O.
    Soruco, A.
    Tielidze, L.
    Usubaliev, R.
    Van Ommen, T.
    Vincent, C.
    Yakovlev, A.
    Historically unprecedented global glacier decline in the early 21st century2015In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 61, no 228, 745-+ p.Article in journal (Refereed)
    Abstract [en]

    Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (similar to 42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (similar to 5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.

  • 6. Akselsson, Cecilia
    et al.
    Olsson, Jonas
    Belyazid, Salim
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Capell, René
    Can increased weathering rates due to future warming compensate for base cation losses following whole-tree harvesting in spruce forests?2016In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 128, no 1-2, 89-105 p.Article in journal (Refereed)
    Abstract [en]

    Whole-tree harvesting, i.e. harvesting of stems, branches and tops, has become increasingly common during recent decades due to the increased demand for renewable energy. Whole-tree harvesting leads to an increase in base cation losses from the ecosystem, which can counteract recovery from acidification. An increase in weathering rates due to higher temperatures is sometimes suggested as a process that may counteract the acidifying effect of whole-tree harvesting. In this study the potential effect of increasing temperature on weathering rates was compared with the increase in base cation losses following whole-tree harvesting in spruce forests, along a temperature gradient in Sweden. The mechanistic model PROFILE was used to estimate weathering rates at National Forest Inventory sites at today's temperature and the temperature in 2050, as estimated by two different climate projections. The same dataset was used to calculate base cation losses following stem-only and whole-tree harvesting. The calculations showed that the increase in temperature until 2050 would result in an increase in the base cation weathering rate of 20-33 %, and that whole-tree harvesting would lead to an increase in base cation losses of 66 % on average, compared to stem-only harvesting. A sensitivity analysis showed that moisture changes are important for future weathering rates, but the effect of the temperature change was dominating even when the most extreme moisture changes were applied. It was concluded that an increase in weathering rates resulting from higher temperatures would not compensate for the increase in base cation losses following whole-tree harvesting, except in the northernmost part of Sweden.

  • 7.
    Alavimoghaddam, Mohammadreza
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Assessing the ability of HEC-HMS rainfall-runoff model to simulate stream flow across Sweden2017Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Computer modeling is the powerful tool for simulating nature’s behavior; however, still more efforts are need for reaching perfect simulation with computer models (especially in the hydrological field of study). In this Master’s thesis, the accuracy of the HEC-HMS computer model for long term rainfall-runoff simulation was evaluated across Sweden. Five different catchments from north to south of Sweden were selected and then simulation have done for 34 years of available data. Simulation was conducted using daily, monthly and yearly time scale resolutions. Results from the north to the south of Sweden were completely different. Simulated runoff and observed runoff in northern catchments followed the same pattern over different time scales but in the southern part of Sweden the results had different patterns in space and time. The best results with HEC-HMS were found in the northern catchments with steep main river slopes. In the southern catchments the model could not predict runoff in any realistic manner at any time and space scale. In total the HEC-HMS model cannot simulate the rainfall runoff for long periods of simulation across Sweden. This is especially true in southern parts of the country dominate with low elevation catchments. However, with regards to its ability for event-based simulation HEC-HMS could be a suitable tool to simulate flood event discharges that are needed for road or other hydraulic structures designs. But, this would require significant amounts of calibration and model development.

  • 8. Albert, Aurélie
    et al.
    Auffret, Alistair G.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cosyns, Eric
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    D'hondt, Bram
    Eichberg, Carsten
    Eycott, Amy E.
    Heinken, Thilo
    Hoffmann, Maurice
    Jaroszewicz, Bogdan
    Malo, Juan E.
    Mårell, Anders
    Mouissie, Maarten
    Pakeman, Robin J.
    Picard, Mélanie
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Poschlod, Peter
    Provoost, Sam
    Schulze, Kiowa Alraune
    Baltzinger, Christophe
    Seed dispersal by ungulates as an ecological filter: a trait-based meta-analysis2015In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 124, no 9, 1109-1120 p.Article in journal (Refereed)
    Abstract [en]

    Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filter - which differentially affects individuals according to their characteristics and shapes species assemblages - and that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and non-dispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales.

  • 9. Alfredsson, H.
    et al.
    Clymans, W.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Conley, D. J.
    Estimated storage of amorphous silica in soils of the circum-Arctic tundra region2016In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 30, no 3, 479-500 p.Article in journal (Refereed)
    Abstract [en]

    We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum-Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil reservoir (0-1m depth) in circum-Arctic tundra terrain. At all sites, the vertical distribution of ASi concentrations followed the pattern of either (1) declining concentrations with depth (most common) or (2) increasing/maximum concentrations with depth. Our results suggest that a set of processes, including biological control, solifluction and other slope processes, cryoturbation, and formation of inorganic precipitates influence vertical distributions of ASi in permafrost terrain, with the capacity to retain stored ASi on millennial timescales. At the four study sites, areal ASi storage (0-1m) is generally higher in graminoid tundra compared to wetlands. Our circum-Arctic upscaling estimates, based on both vegetation and soil classification separately, suggest a storage amounting to 219 +/- 28 and 274 +/- 33 Tmol Si, respectively, of which at least 30% is stored in permafrost. This estimate would account for about 3% of the global soil ASi storage while occupying an equal portion of the global land area. This result does not support the hypothesis that the circum-Arctic tundra soil ASi reservoir contains relatively higher amounts of ASi than other biomes globally as demonstrated for carbon. Nevertheless, climate warming has the potential to significantly alter ASi storage and terrestrial Si cycling in the Arctic.

  • 10. Alfredsson, Hanna
    et al.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Clymans, Wim
    Stadmark, Johanna
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Conley, Daniel J.
    Amorphous silica pools in permafrost soils of the Central Canadian Arctic and the potential impact of climate change2015In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 124, no 1-3, 441-459 p.Article in journal (Refereed)
    Abstract [en]

    We investigated the distribution, storage and landscape partitioning of soil amorphous silica (ASi) in a central Canadian region dominated by tundra and peatlands to provide a first estimate of the amount of ASi stored in Arctic permafrost ecosystems. We hypothesize that, similar to soil organic matter, Arctic soils store large amounts of ASi which may be affected by projected climate changes and associated changes in permafrost regimes. Average soil ASi storage (top 1 m) ranged between 9600 and 83,500 kg SiO2 ha(-1) among different land-cover types. Lichen tundra contained the lowest amounts of ASi while no significant differences were found in ASi storage among other land-cover types. Clear differences were observed between ASi storage allocated into the top organic versus the mineral horizon of soils. Bog peatlands, fen peatlands and wet shrub tundra stored between 7090 and 45,400 kg SiO2 ha(-1) in the top organic horizon, while the corresponding storage in lichen tundra, moist shrub- and dry shrub tundra only amounted to 1500-1760 kg SiO2 ha(-1). Diatoms and phytoliths are important components of ASi storage in the top organic horizon of peatlands and shrub tundra systems, while it appears to be a negligible component of ASi storage in the mineral horizon of shrub tundra classes. ASi concentrations decrease with depth in the soil profile for fen peatlands and all shrub tundra classes, suggesting recycling of ASi, whereas bog peatlands appeared to act as sinks retaining stored ASi on millennial time scales. Our results provide a conceptual framework to assess the potential effects of climate change impacts on terrestrial Si cycling in the Arctic. We believe that ASi stored in peatlands are particularly sensitive to climate change, because a larger fraction of the ASi pool is stored in perennially frozen ground compared to shrub tundra systems. A likely outcome of climate warming and permafrost thaw could be mobilization of previously frozen ASi, altered soil storage of biogenically derived ASi and an increased Si flux to the Arctic Ocean.

  • 11. Ameli, Ali A.
    et al.
    Beven, Keith
    Erlandsson, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Creed, Irena F.
    McDonnell, Jeffrey J.
    Bishop, Kevin
    Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone2017In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 53, no 1, 942-960 p.Article in journal (Refereed)
    Abstract [en]

    The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flow path dynamics drive the spatiotemporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flow paths are complex and difficult to map quantitatively. Here we couple a new integrated flow and particle tracking transport model with a general reversible Transition State Theory style dissolution rate law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (K-s) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration ( Ceq) to intrinsic weathering rate ( Rmax), vertical heterogeneity in K-s enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As <mml:mfrac>CeqRmax</mml:mfrac> decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behavior, regardless of the degree of vertical heterogeneity in K-s. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as <mml:mfrac>CeqRmax</mml:mfrac> decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).

  • 12. Anchukaitis, Kevin J.
    et al.
    Wilson, Rob
    Briffa, Keith R.
    Buntgen, Ulf
    Cook, Edward R.
    D'Arrigo, Rosanne
    Davi, Nicole
    Esper, Jan
    Frank, David
    Gunnarson, Björn E.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hegerl, Gabi
    Helama, Samuli
    Klesse, Stefan
    Krusic, Paul J.
    Stockholm Univ, Dept Phys Geog, Stockholm, Sweden.
    Linderholm, Hans W.
    Myglan, Vladimir
    Osborn, Timothy J.
    Zhang, Peng
    Rydval, Milos
    Schneider, Lea
    Schurer, Andrew
    Wiles, Greg
    Zorita, Eduardo
    Last millennium Northern Hemisphere summer temperatures from tree rings: Part II, spatially resolved reconstructions2017In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 163, 1-22 p.Article, review/survey (Refereed)
    Abstract [en]

    Climate field reconstructions from networks of tree-ring proxy data can be used to characterize regional scale climate changes, reveal spatial anomaly patterns associated with atmospheric circulation changes, radiative forcing, and large-scale modes of ocean-atmosphere variability, and provide spatiotemporal targets for climate model comparison and evaluation. Here we use a multiproxy network of tree-ring chronologies to reconstruct spatially resolved warm season (May August) mean temperatures across the extratropical Northern Hemisphere (40-90 degrees N) using Point-by-Point Regression (PPR). The resulting annual maps of temperature anomalies (750-1988 CE) reveal a consistent imprint of volcanism, with 96% of reconstructed grid points experiencing colder conditions following eruptions. Solar influences are detected at the bicentennial (de Vries) frequency, although at other time scales the influence of insolation variability is weak. Approximately 90% of reconstructed grid points show warmer temperatures during the Medieval Climate Anomaly when compared to the Little Ice Age, although the magnitude varies spatially across the hemisphere. Estimates of field reconstruction skill through time and over space can guide future temporal extension and spatial expansion of the proxy network.

  • 13.
    Anderberg, Niklas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Betesmarker i Mjölkkrisens Sverige: Mjölkbönder och betesmarken, landskapet och framtiden2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The situation for Swedish dairy farmers has been difficult since 2014. Many are choosing to close down their businesses. At the same time, Sweden has experienced a reduction of important habitats consisting of grazing lands, a trend that is still ongoing. This study explores how dairy farmers look at grasslands, their values, management, and future. Through interviews with dairy farmers it investigates how farmers look at the systems of environmental compensation awarded for the management of pastures and grassland habitats. The study concludes that is primarily an aesthetic landscape value that is the main reason behind the desire to preserve pastures amongst farmers. This can be linked to a personal relationship between the farmers and the landscape he/she grew up in and help create through with their work. Any reduction in grasslands has not been observed by a majority of the interviewed farmers, despite the fact that such a reduction is occurring in their counties as a whole. This suggests that the situation can vary widely at a local level. The opinions concerning the environmental compensations vary among the interviewees, but overall there is a wish for a less bureaucratic system that provides more flexibility for the farmer. This wish for less bureaucracy is also found concerning the system around the law demanding that all cows should be allowed to graze during a period of the year. In the end, it seems important for the future of grazinglands and the habitats they create that profitability returns to the dairy farmers, since without farmers grazing will be further reduced. Today’s difficult situation for the farmers increases the risk of it being difficult to find the workforce of future farmers who are willing and able to perform the work that is done today.

  • 14.
    Andréen, Sigrid
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The development of landscape structures affecting biodiversity in the Hanveden and Tyresta green wedges2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The green wedges of Stockholm are meant to support a high level of biodiversity as well as cultural and recreational services but evaluating the spatial development of the wedges is difficult because their delineation has changed since they were first used in a regional development plan. This study examines a part of the Hanveden and Tyresta wedges in southern Stockholm, with the goal to use robust ecological theory to evaluate the development of the wedges from 1992 until today with focus on conserving a high level of biodiversity. Using an already existing GIS-based method of identifying connectivity weaknesses in the wedges, more weaknesses were found in 2010 than in 1992 although the total area of the wedges had only declined 3.3%. The shape of the wedges had also changed, with more narrow parts in 2010 than in 1992. To more effectively compare the development of factors in the landscape that are relevant for biodiversity, this study proposes a new method using the common shrew and hazel grouse as surrogate species. The total area loss for the common shrew was 2.96% from 1991 to 2013 and 2.23% for the hazel grouse. Fragmentation increased for both species. A large part of the greenspaces relevant to the surrogate species are covered by the green wedges, meaning that important cultural and recreational values identified by the county council are also present in areas relevant to the surrogate species. Using surrogate species to delineate and monitor the green wedges could enhance the cultural and recreational qualities of the wedges, emphasize the need for connectivity planning, identify ecologically important parts of the greenspaces as well as provide a tool for following up the development of the urban greenspaces of Stockholm. However, formulating goals relevant to biodiversity is important to fully evaluate development and municipal cooperation is needed.

  • 15.
    Antikainen, Catarina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Formation and Retention of Soil Organic Matter (SOM) in the Taygetos Mountains (Greece): Influence of Soil Properties and Wildfire2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Deforestation and soil degradation is a worldwide problem, and especially so in the Greek Taygetos mountains. With wildfires affecting thousands of square kilometers of land, soil quality assessments are important in order to choose the right land management measures in the process of landscape restoration. Soil organic matter (SOM) is a good indicator of soil quality, but its response to wildfires and dependence on other soil properties is not well known in the Taygetos area. This study attempts to investigate the influence of topographic aspect and slope inclination on SOM formation and retention in fire damaged forests. Results are put into context with other soil properties such as pH and water content as well as the influence of wildfires. The study found unexpectedly high amounts of SOM in all sampled slopes, which was attributed to the incorporation of charcoal from burnt litter produced during low intense fires. No correlation was detected between SOM and aspect, and only a weak negative correlation between SOM and slope inclination. However, the study found a strong correlation between SOM amounts and water content, which suggests that water is one of the main limiting factors of SOM in the Taygetos mountains.

  • 16.
    Ardung, Ola
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Closed To Open Sourve GIS: First Steps In Reverse Engineering ESRI's Layer Defintion File Format2017Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Visualization of digital geographic data is often accomplished through custom symbology that is saved in a proprietary format called a layer file (.lyr). The sharing of free geographical information system (GIS) data can be limited as the symbology data is bound inthe .lyr file format. This makes it harder and more tedious to work with open software tools since it is not possible to convert or open the .lyr file in free and open GIS software and thus limits the distribution of free GIS data. The aim of this thesis is to increase the interoperability of .lyr data between proprietary and free and open GIS software. This was done by revers eengineering the .lyr file format to document the file structure and to distribute the knowledge and metadata gained from this project to the open source community. Reverse engineering the.lyr format provided a well needed metadata and documentation about the format which increases the interoperability and enable future work to continue to lessen the gap between open source and commercial software. This groundwork can therefore, enable a continued development of data interoperability between proprietary and free and open GIS software.

  • 17.
    Arleskär, Staffan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bostadsrätt, gräsmark eller skog?: Hur har exploatering för bostadsbyggande år 2000-2015 påverkat Järvakilens funktion som spridningsväg?2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Urbanization is a key driver of habitat loss, ecosystem degradation and has a great impact on biodiversity. Exploitation of buffer zones surrounding conservation areas and green structures in urban environment can affect biodiversity through reduced total area of habitat, increased edge effects and lost connectivity on a landscape level. The previous regional development plans for the Stockholm region, had the purpose of leaving large green structures undeveloped to secure core areas of great biological value by focusing on a dense city core. However, the latest regional development strategy puts stress on the green wedges by shifting the focal areas of the development into suburban regional city centers, in many cases close to the green wedges. The purpose of this study was to map habitat loss and changes in the total area of the Järva green wedge, west of Stockholm, caused by development of housing areas in previously sparsley exploited buffer zones, during the period 2000 – 2015. The study uses theories of landscape ecology, remote sensing and GIS to map and quantify habitat loss between 2000 and 2015. Two different birds were used as surrogate species, one grassland habitat specialist – Corncrake (Crex crex) and one forest habitat generalist – Eurasian jay (Garrulus glandarius). The two different surrogate species were used to identify how loss of two nature types could influence biodiversity and connectivity for a group of species. Documents and development plans on regional and local scale were also used to map and predict further habitat loss and exploitation of the green wedge until 2030. The result of the study shows that grassland habitat lost nearly twice the area than forest habitat due to development of housing areas during the period 2000 to 2015. A total of 1.3 km² of grassland and 0.7 km² forest habitat were replaced by housing areas during the fifteen years covered in the study, and the Järva green wedge will have lost a total of 3.84 km² buffer zones by the year 2030. The Corncrake and other grassland specialist species is likely to get most affected when grassland suffered the greatest habitat loss in the area. Even though the Eurasian jay has a key ecological function for the Oak forest in the Järva green wedge and relies on forest habitat for successful breeding, the loss of forest habitat will probably not affect the habitat generalist species in the same way. On a regional scale, the study suggests that habitat loss and fragmentation may affect grassland specialist species more than forest generalist species. The overall connectivity in the Järva green wedge is likely to get affected by a shrinking total area caused by narrowing of the green wedge until 2030. The function of the Järva green wedge as a dispersal corridor for biodiversity in the Stockholm region will most certainly get affected by further loss of buffer zones caused by exploitation of land for housing areas.

  • 18.
    Aronsson, Johanna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Användning av tredimensionell geologisk modellering i hydrogeologiska utredningar: En fallstudie inför anläggandet av ett akviferlager i Brunkebergsåsen i Stockholm2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Akviferlager är en form av geoenergi där solenergi lagrad i grundvattnet används för att värma och kyla byggnader. Inför anläggandet av ett akviferlager är det viktigt med grundläggande geologiska och hydrogeologiska utredningar för att säkerställa funktion och kapacitet hos akviferlagret, samt minimera eventuell miljöpåverkan. I denna studie utvecklas en tredimensionell geologisk modell för att öka kunskapen om rullstensåsens geologiska uppbyggnad samt bedöma hur geologin kan komma att påverka det planerade akviferlagret. För att undersöka vilken påverkan manuella justeringar och tolkningar av geologin har, togs två geologiska modeller fram för jämförelse. Utifrån de geologiska modellerna uppskattades effektiv hydraulisk konduktivitet för åsen, d.v.s. sammanlagd konduktivitet för hela akviferens mäktighet, samt transporttid mellan akviferlagrets brunnspoler. Studien visar att akviferen består av sammanhängande jordlager med hög hydraulisk konduktivitet. Beroende på tolkningar och justeringar i modelleringsprocessen visar de två olika modellerna på skillnader vad gäller jordlagrens utbredning och mäktighet. Detta medför skillnader i effektiv hydraulisk konduktivitet mellan modellerna, vilket resulterar i relativt stora skillnader vad gäller transporttider mellan brunnspolerna. Tredimensionella geologiska modeller bedöms bidra till förbättrade hydrogeologiska utredningar då det är ett enkelt och effektivt sätt att bygga upp ett områdes geologi för översikt, tolkning och vidare studier i form av exempelvis grundvattenmodellering.

  • 19.
    Asokan, Shilpa M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rogberg, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography. University of New Hampshire, USA.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Climate model performance and change projection for freshwater fluxes: comparison for irrigated areas in Central and South Asia2016In: Journal of Hydrology Regional Studies, ISSN 1070-9428, E-ISSN 1857-8489, Vol. 5, 48-65 p.Article in journal (Refereed)
    Abstract [en]

    Study region: The large semi-arid Aral Region in Central Asia and the smaller tropical Mahanadi River Basin (MRB) in India. Study focus: Few studies have so far evaluated the performance of the latest generation ofglobal climate models on hydrological basin scales. We here investigate the performanceand projections of the global climate models in the Coupled Model Intercomparison Project, Phase 5 (CMIP5) for freshwater fluxes and their changes in two regional hydrological basins, which are both irrigated but of different scale and with different climate. New hydrological insights for the region: For precipitation in both regions, model accuracy relative to observations has remained the same or decreased in successive climate model generations until and including CMIP5. No single climate model out-performs other models across all key freshwater variables in any of the investigated basins. Scale effects are not evident from global model application directly to freshwater assessment for the two basins of widely different size. Overall, model results are less accurate and more uncertain for freshwater fluxes than for temperature, and particularly so for model-implied water storage changes. Also, the monsoon-driven runoff seasonality in MRB is not accurately reproduced. Model projections agree on evapotranspiration increase in both regions until the climatic period 2070–2099. This increase is fed by precipitation increase in MRB and by runoff water (thereby decreasing runoff) in the Aral Region.

  • 20.
    Assefa Hassen, Yohannes
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The Impacts of Mining on Arctic Environment and Society from Corporate Social Responsibility and Sustainable Development Perspectives: The Case of Jokkmokk (Kallak) Iron Mines in Northern Sweden2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Extractive industry in Arctic is controversial due  to the ecosystems and communities in the region are highly sensitive to natural and anthropogenic disturbances as it is one of the world’s global change hot-spots, as well as its uniqueness and distinctive social and ecological significance. As mining industry has developed into sophisticated operations, yet the basic causes of environmental pollution and degradation and impacts on the natural environment of the Arctic region remain unchanged. Mining in this environment may be faced with dilemmas as the result of adverse impacts they may cause and their escalating environmental footprints;  as well as reactions from pressure groups and indigenous peoples, which in turn may have a detrimental effect on their reputations and financial performances. This may further have social, environmental and political risks in their present and future roles and operations. Thus, the mining industry ought to recognize the impacts in their operations, and are required to work towards minimizing the adverse impacts and maximizing the substantial benefits of their actions on the environment, the community and local people. Corporate social responsibility (CSR) and sustainability are supposed to be two of several principles used to examine the social and environmental endeavours and results of business activity.

    The aim of this thesis is to assess the environmental and social impacts associated with major mining operations Arctic region, and to conduct preliminary review of the perspectives of CSR and sustainable development in countries across the Arctic region and subarctic, especially the United States of America (USA), Finland and Sweden. As well as conduct comparative study and analysis on how corporate entities in these countries dealing with the two theoretical frameworks and how they are approached in practice and managed, and information are disclosed. The study also concentrates on how these issues can be handled in the case of Jokkmokk (Kallak) Iron Mines in Sweden. Different methodological approaches and techniques have been adopted in this study. The literature review is supplemented by interviews with strategically important stakeholders. The Environmental Impact Assessment (EIA) statement is reviewed and conceptual modeling is also employed to demonstrate the dynamic effects and consequences of the Kallak North Iron Mines. The findings in this thesis propose that the corporations’ in the USA show differences from those of the European countries in defining and  addressing social and environmental concerns; as well as managing CSR and sustainability issues and communicating them as there are qualitatively different practices and approaches to CSR in these countries. In conclusion, main points are suggested as important recommendations entailing of some clear expectations to fulfill on how CSR and sustainability issues may be handled by extractive industry including the case of Jokkmokk (Kallak North) Iron Mines. 

  • 21.
    Auffret, Alistair G.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Aggemyr, Elsa
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Spatial scale and specialization affect how biogeography and functional traits predict long-term patterns of community turnover2017In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 31, no 2, 436-443 p.Article in journal (Refereed)
    Abstract [en]

    1. Immigration, extirpation and persistence of individual populations of species are key processes determining community responses to environmental change. However, they are difficult to study over long time periods without corresponding historical and modern-day species occurrences.

    2. We used historical and present-day plant species occurrence data from two different spatial scales (resolutions) to investigate the plant community turnover during the 20th century in a Baltic Sea archipelago. Patterns of turnover were analysed in relation to plant functional traits relating to dispersal and competition/persistence, as well as biogeographical variables.

    3. Turnover was largely driven by interactions between functional traits and measures of area, connectivity and distance to mainland. However, the combinations of traits and biogeographical variables that were most important for predicting immigration and extirpation differed between data sets, and between species associated with grassland management and the entire species pool.

    4. Taller plants were more likely to persist regardless of scale and biogeography, reflecting the grazing abandonment that occurred in the study area. Interactions between dispersal traits and biogeography were related to immigrations when the entire species pool was considered. However, increased dispersal potential, a smaller island size and increasing distance to mainland combined to promote extirpations in management-associated species. A perennial life span and seed banking contributed to species persistence. At the larger spatial scale, trait-driven turnover was not mediated by the biogeographical context.

    5. We showed that it is important to consider functional traits, biogeographical variables and their interactions when analysing community turnover over time. Furthermore, we found that the understanding of how combinations of traits and biogeography predict turnover depends on the source and spatial scale of the available data, and the species pool analysed.

  • 22. Augustsson, A.
    et al.
    Söderberg, Uddh T.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Åström, M.
    Olofsson, B.
    Balfors, B.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The risk of overestimating the risk-metal leaching to groundwater near contaminated glass waste deposits and exposure via drinking water2016In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 566, 1420-1431 p.Article in journal (Refereed)
    Abstract [en]

    This study investigates metal contamination patterns and exposure to Sb, As, Ba, Cd and Pb via intake of drinking water in a region in southeastern Sweden where the production of artistic glass has resulted in a large number of contaminated sites. Despite high total concentrations of metals in soil and groundwater at the glassworks sites properties, all drinking water samples from households with private wells, located at a 30-640 m distance from a glassworks site, were below drinking water criteria from the WHO for Sb, As, Ba and Cd. A few drinking water samples showed concentrations of Pb above the WHO guideline, but As was the only element found in concentrations that could result in human exposure near toxicological reference values. An efficient retention of metals in the natural soil close to the source areas, which results in a moderate impact on local drinking water, is implied. Firstly, by the lack of significant difference in metal concentrations when comparing households located upstream and downstream of the main waste deposits, and secondly, by the lack of correlation between the metal concentration in drinking water and distance to the nearest glassworks site. However, elevated Pb and Cd concentrations in drinking water around glassworks sites when compared to regional groundwater indicate that diffuse contamination of the soils found outside the glassworks properties, and not only the glass waste landfills, may have a significant impact on groundwater quality. We further demonstrate that different mobilization patterns apply to different metals. Regarding the need to use reliable data to assess drinking water contamination and human exposure, we finally show that the conservative modelling approaches that are frequently used in routine risk assessments may result in exposure estimates many times higher than those based on measured concentrations in the drinking water that is actually being used for consumption.

  • 23.
    Axelsson, Pia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Minskad trädtillväxt under Lilla sitiden?: En dendroklimatologisk jämförelse mellan nutid och 1600-talet invid trädgränsen i norra Skandinavien2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    During the period called Little Ice Age (1400 ~ 1900) the climate of northern Europe was in an annual year-basis overall colder than it was before and after that period. The numbers of short, cold and rainy summers and long, bitter-cold winters where often repetitive under the approximately 500-years the period lasted. In Scandinavia, the coldest time during this period is estimated to have started around the end of the 16th century and lasted to the beginning of the 18th century. Trees growing at the tree-line are limited by temperature for their annual growth and hence showing differences of growth during changes in the climate,  a method called dendroclimatology. The variations of growth can be read in the tree-rings either by analyze the width of the ring or by look into the density of the wood and is used to reconstruct past climates. The aim of this study is to investigate how the tree-growth responded to the colder temperatures compared to today. Trees (Scots pine) close to the tree-line in northern Scandinavia where used to enhance the temperature signal in the data.  The proxy used is the growth density (MXD – maximum latewood density). The result reveals that during the coldest century, the trees show a larger number of negative growth-years with comparison with the 20th century and the negative and positive growth follows a more united trend. The result also shows a great number of negative growth-years at the end of the Little Ice Age, with a lot of extreme low growth - indexes (lower than -1.5). The conclusion then leans towards a cooler climate with overall lower temperatures under the 17th century compared to 1900-2004. 

  • 24.
    Axiotou, Anna-Maria
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Enkätundersökning om attityder gentemot källsortering bland invånarna i Kiruna centralort2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Recycling is one of the most significant action we can do to reduce the environmental impactof waste. More efficient use of natural resources and the reduced greenhouse gas emissions is two major environmental benefits. The people that live on this planet have a key role in increasing recycling by sorting their household waste. Therefore, residents must take a responsibility for their consumption and the use of the planets resources. People's attitudes tosort waste is therefore essential for understand recycling behaviour and intensions.

    This study aims to examine waste recycling behaviour, with a focus on attitudes and factors that affect the recycling behaviour among residents in Kiruna, the northern most municipalityof Sweden. 97 inhabitants in the central part of Kiruna participated in the survey. It was found that lack of recycling stations and curbside collection were factors that affected people to recycle. The study also showed that the residents had a positive attitude to recycle because ofthe level of knowledge about the benefits of recycling.

  • 25. Bagger-Sjöbäck, Dan
    et al.
    Strömbäck, Karin
    Hakizimana, Pierre
    Plue, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Larsson, Christina
    Hultcrantz, Malou
    Papatziamos, Georgios
    Smeds, Henrik
    Danckwardt-Lillieström, Niklas
    Hellström, Sten
    Johansson, Ann
    Tideholm, Bo
    Fridberger, Anders
    A Randomised, Double Blind Trial of N-Acetylcysteine for Hearing Protection during Stapes Surgery2015In: PLoS ONE, ISSN 1932-6203, Vol. 10, no 3, e0115657Article in journal (Refereed)
    Abstract [en]

    Background Otosclerosis is a disorder that impairs middle ear function, leading to conductive hearing loss. Surgical treatment results in large improvement of hearing at low sound frequencies, but high-frequency hearing often suffers. A likely reason for this is that inner ear sensory cells are damaged by surgical trauma and loud sounds generated during the operation. Animal studies have shown that antioxidants such as N-Acetylcysteine can protect the inner ear from noise, surgical trauma, and some ototoxic substances, but it is not known if this works in humans. This trial was performed to determine whether antioxidants improve surgical results at high frequencies. Methods We performed a randomized, double-blind and placebo-controlled parallel group clinical trial at three Swedish university clinics. Using block-stratified randomization, 156 adult patients undergoing stapedotomy were assigned to intravenous N-Acetylcysteine (150 mg/kg body weight) or matching placebo (1:1 ratio), starting one hour before surgery. The primary outcome was the hearing threshold at 6 and 8 kHz; secondary outcomes included the severity of tinnitus and vertigo. Findings One year after surgery, high-frequency hearing had improved 2.7 +/- 3.8 dB in the placebo group (67 patients analysed) and 2.4 +/- 3.7 dB in the treated group (72 patients; means +/- 95% confidence interval, p = 0.54; linear mixed model). Surgery improved tinnitus, but there was no significant intergroup difference. Post-operative balance disturbance was common but improved during the first year, without significant difference between groups. Four patients receiving N-Acetylcysteine experienced mild side effects such as nausea and vomiting. Conclusions N-Acetylcysteine has no effect on hearing thresholds, tinnitus, or balance disturbance after stapedotomy.

  • 26. Bartsch, Annett
    et al.
    Widhalm, Barbara
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Siewert, Matthias Benjamin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Can C-band synthetic aperture radar be used to estimate soil organic carbon storage in tundra?2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 19, 5453-5470 p.Article in journal (Refereed)
    Abstract [en]

    A new approach for the estimation of soil organic carbon (SOC) pools north of the tree line has been developed based on synthetic aperture radar (SAR; ENVISAT Advanced SAR Global Monitoring mode) data. SOC values are directly determined from backscatter values instead of upscaling using land cover or soil classes. The multi-mode capability of SAR allows application across scales. It can be shown that measurements in C band under frozen conditions represent vegetation and surface structure properties which relate to soil properties, specifically SOC. It is estimated that at least 29 Pg C is stored in the upper 30 cm of soils north of the tree line. This is approximately 25% less than stocks derived from the soil-map-based Northern Circumpolar Soil Carbon Database (NCSCD). The total stored carbon is underestimated since the established empirical relationship is not valid for peatlands or strongly cryoturbated soils. The approach does, however, provide the first spatially consistent account of soil organic carbon across the Arctic. Furthermore, it could be shown that values obtained from 1 km resolution SAR correspond to accounts based on a high spatial resolution (2 m) land cover map over a study area of about 7 x 7 km in NE Siberia. The approach can be also potentially transferred to medium-resolution C-band SAR data such as ENVISAT ASAR Wide Swath with similar to 120m resolution but it is in general limited to regions without woody vegetation. Global Monitoring-mode-derived SOC increases with unfrozen period length. This indicates the importance of this parameter for modelling of the spatial distribution of soil organic carbon storage.

  • 27. Baskaran, Preetisri
    et al.
    Hyvönen, Riitta
    Berglund, S. Linnea
    Clemmensen, Karina E.
    Ågren, Göran I.
    Lindahl, Björn D.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Modelling the influence of ectomycorrhizal decomposition on plant nutrition and soil carbon sequestration in boreal forest ecosystems2017In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 213, no 3, 1452-1465 p.Article in journal (Refereed)
    Abstract [en]

    Tree growth in boreal forests is limited by nitrogen (N) availability. Most boreal forest trees form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve the uptake of inorganic N and also have the capacity to decompose soil organic matter (SOM) and to mobilize organic N (ECM decomposition'). To study the effects of ECM decomposition' on ecosystem carbon (C) and N balances, we performed a sensitivity analysis on a model of C and N flows between plants, SOM, saprotrophs, ECM fungi, and inorganic N stores. The analysis indicates that C and N balances were sensitive to model parameters regulating ECM biomass and decomposition. Under low N availability, the optimal C allocation to ECM fungi, above which the symbiosis switches from mutualism to parasitism, increases with increasing relative involvement of ECM fungi in SOM decomposition. Under low N conditions, increased ECM organic N mining promotes tree growth but decreases soil C storage, leading to a negative correlation between C stores above- and below-ground. The interplay between plant production and soil C storage is sensitive to the partitioning of decomposition between ECM fungi and saprotrophs. Better understanding of interactions between functional guilds of soil fungi may significantly improve predictions of ecosystem responses to environmental change.

  • 28.
    Belin, Klas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Exkursioners bidrag till elevers kunskapsutveckling: En klassificering av exkursionsguider med hjälp av Blooms reviderade taxonomi2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna studie syftar till att ta reda på vilka kunskaper och kognitiva processer elever kan få underexkursioner i ämnet geografi. Utöver detta undersöktes hur exkursioner bedrivs i Stockholms län.Undersökningen genomfördes genom en insamling av exkursionsguider som sedan analyserades medhjälp av Blooms reviderade taxonomi. För att få ett bredare underlag kring hur exkursioner utövasskickades webbenkäter ut till ett flertal lärare.Överlag är begreppskunskapen den mest framträdande kunskapen under de undersökta exkursionernavilket stämmer överens med den tidigare forskningen inom detta område. Exkursionsguiderna visaräven att majoriteten av exkursionsuppgifterna vill få eleven till den lägre nivån av kognitivt tänkande ioch med att uppgifterna syftar till att eleven ska förstå begrepp. Resultatet visar dock att det finns entendens att elever ges en möjlighet till en högre nivå av tänkande under de exkursioner där eleven äraktiv och försöker hitta svar på uppgifterna de fått av läraren.

  • 29.
    Bennich, Therese
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Belyazid, Salim
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The Route to Sustainability-Prospects and Challenges of the Bio-Based Economy2017In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 9, no 6, 887Article, review/survey (Refereed)
    Abstract [en]

    The bio-based economy has been increasingly recognized in the sustainability debate over the last two decades, presented as a solution to a number of ecological and social challenges. Its premises include climate change mitigation, cleaner production processes, economic growth, and new employment opportunities. Yet, a transition to a bio-based economy is hampered by risk factors and uncertainties. In this paper, we explore the concept of a bio-based economy, focusing on opportunities of achieving sustainability, as well as challenges of a transition. Departing from an understanding of sustainability provided by the weak and strong sustainability paradigms, we first outline the definition and development of the bio-based economy from a theoretical perspective. Second, we use Sweden as an example of how a transition towards a bio-based economy has been evolving in practice. The review indicates that the proposed direction and strategies of the bio-based economy are promising, but sometimes contradictory, resulting in different views on the actions needed for its premises to be realized. Additionally, current developments adhere largely to the principles of the weak sustainability paradigm. In order for the bio-based economy to develop in accordance with the notion of strong sustainability, important steps to facilitate a transition would include acknowledging and addressing the trade-offs caused by biophysical and social limits to growth.

  • 30.
    Berg, Håkan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Nguyen, Thanh Tam
    Stockholm University, Faculty of Science, Department of Physical Geography. Nong Lam University, Vietnam.
    Use of pesticides and attitude to pest management strategies among rice and rice-fish farmers in the Mekong Delta, Vietnam2012In: International Journal of Pest Management, ISSN 0967-0874, E-ISSN 1366-5863, Vol. 58, no 2, 153-164 p.Article in journal (Refereed)
    Abstract [en]

    This study assesses the use of pesticides and attitude to pest management strategies among rice and rice-fish farmersin Can Tho’ and Tien Giang provinces of the Mekong Delta, Vietnam, in 2007. A comparison is made to a similarstudy in 1999, in order to identify changes in patterns of pesticide use and possible influences of integrated pestmanagement (IPM) programmes and brown planthopper (a major pest) outbreaks. One hundred and twenty farmersused 66 different pesticides, similar to the 64 pesticides recorded as being used in the 1999 survey. Nine of the 10 mostpopular pesticides in 2007 were the same as those found to be popular in 1999. Insecticides are used by 73–95% ofthe farmers, which is the most commonly employed type of pesticide. The number of applications of both herbicidesand fungicides has more than halved since 1999 for all farmers, while insecticide applications has doubled for IPMfarmers (those with prior training in IPM methodology). Similarly, the average dose of active ingredient (a.i.) ofinsecticides per crop has decreased slightly for non-IPM rice farmers, while it has more than doubled among IPMfarmers, resulting in almost the same amount of a.i. per crop for all groups of farmers (insecticides 0.6, fungicides 0.5,and herbicides 0.3 kg a.i. ha71 crop71). Overall, the results indicate a temporal trend for more selective use ofpesticides and an increased awareness among non-IPM farmers of the negative side effects of pesticide use.

  • 31.
    Berg, Håkan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Söderholm, Agnes Ekman
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Söderström, Anna-Sara
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Tam, Nguyen Thanh
    Stockholm University, Faculty of Science, Department of Physical Geography. Nong Lam University, Vietnam.
    Recognizing wetland ecosystem services for sustainable rice farming in the Mekong Delta, Vietnam2017In: Sustainability Science, ISSN 1862-4065, E-ISSN 1862-4057, Vol. 12, no 1, 137-154 p.Article in journal (Refereed)
    Abstract [en]

    The increased rice production in the Mekong Delta during the last two decades has improved agricultural income and reduced poverty, but it has also had negative impacts on the environment and human health. This study shows that integrated rice-fish farming and integrated pest management strategies provide sustainable options to intensive rice farming, because of a more balanced use of multiple ecosystem services that benefit the farmers' health, economy and the environment. The study investigates and compares farming strategies among 40 rice and 20 rice-fish farmers in two locations in the Mekong Delta. Production costs and income are used to compare the systems' financial sustainability. The farmers' perception on how their farming practices influence on ecosystem services and their livelihoods are used as an indication of the systems' ecological and social sustainability. Although rice-fish farmers used lower amount of pesticides and fertilisers than rice farmers, there were no statistical differences in their rice yields or net income. Rice was seen as the most important ecosystem service from rice fields and related wetlands, but also several other ecosystem services, such as water quality, aquatic animals, plants, habitats, and natural enemies to pests, were seen as important to the farmers' livelihoods and wellbeing. All farmers perceived that there had been a general reduction in all these other ecosystem services, due to intensive rice farming during the last 15 years, and that they will continue to decline. The majority of the farmers were willing to reduce their rice yields slightly for an improved quality of the other ecosystem services.

  • 32.
    Berggren, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Inledande försökt till mätning med Europas navigeringssystem Galileo2016Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Europe is presently building up a satellite navigation system of their own, Galileo. Unlike the American system, GPS, and the Russian system, Glonass, Galileo will be a civilian system. It will be independent from, but interoperable with both GPS and Glonass. After many delays have enough satellites been launched and placed in orbit to make it possible to start up Galileo’s initial services during December 2016.

    This study gives an account of the construction and development of the Galileo system. During two weeks in the spring 2016 experimental RTK measurements were made with Galileo combined with GPS where the satellite corrections were distributed from Lantmäteriet’s (the Swedish mapping, cadastral and land registration authority’s) supportsystem for satellite positioning, SWEPOS. The measurements were carried out with singlestation RTK towards a SWEPOS reference station at Mosebacke on Södermalm in Stockholm. The rover was placed over a fixed point about 1.2 km from the reference station.The purpose of the study was to determine if it was possible in the spring 2016 to make any measurements with Galileo and to see what Galileo can add to RTK measurements combined with GPS in SWEPOS.

    During the spring 2016 it was not possible to make any measurements with only Galileo satellites due to the fact that there were too few satellites in orbit. The results from the measurements indicate that combining Galileo and GPS could be positive for network RTK in SWEPOS. The part of achieved fixed solutions increases, the average time until fixed solution is achieved shortens and the space vehicle geometry (PDOP) gets a better value when combining GPS and Galileo. It is however too soon to say anything certain about the influence of Galileo on the position uncertainty.

  • 33.
    Bergström, Catrin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hälsorisker med avsaltat dricksvatten från Östersjön2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Brist på dricksvatten är ett hot som finns på många platser runtomkring i världen, även iflera områden i Sverige. En effekt av detta är att avsaltningstekniken har blivit en alltvanligare metod för att trygga dricksvattenförsörjningen och en växande gruppmänniskor konsumerar nu avsaltat dricksvatten. Avsaltat dricksvatten är dock en ganskany lösning på dricksvattenproblematiken i Sverige och det finns relativt lite forskningom vilka hälsorisker det kan finnas med att använda Östersjön som råvattenkälla. Syftetmed denna rapport är att öka kunskapen om potentiella hälsorisker med avsaltatdricksvatten från Östersjön. Den centrala frågeställningen handlar om vilka erfarenheteroch forskning om hälsorisker med avsaltat dricksvatten det finns och vilka hälsoriskersom kan finnas när Östersjön används som råvattenkälla i avsaltningsverk. Denlitteratur och information som ligger till grund för resultatet i denna rapport inhämtadesgenom litteratursökningar och genom att sakkunniga experter och tjänstemänkonsulterades. Resultaten i denna rapport visar bland annat att avsaltningsteknikenöverlag är en effektiv metod för att avskilja många typer av olika oönskade ochohälsosamma ämnen i dricksvatten. Avskiljningsgraden för alger och algtoxin iavsaltningsverk är hög, men det kan förekomma låga halter av alger och algtoxin idricksvatten från anläggningar med bristande underhåll. Vidare visar resultaten att detfinns indikationer på att konsumtion av avsaltat dricksvatten istället för vanligtdricksvatten kan vara ofördelaktigt för vissa individer eftersom avsaltat dricksvattenofta är mineralfattigt. De slutsatser som kan dras är bland annat att avsaltningsteknikenavskiljer många miljöföroreningar och andra ohälsosamma ämnen som finns iÖstersjöns havsvatten. Vidare bör försiktighet tillämpas eftersom låg avskiljningsgradav ännu okända föroreningar i Östersjön och potentiella hälsoeffekter av dessa inte kanuteslutas. Dessutom går det i nuläget inte att avgöra vilka hälsorisker låga halter avalger och algtoxin i dricksvatten från avsaltningsverk i dåligt skick skulle kunna föramed sig. Till sist kan slutsatsen dras att dricksvatten kan vara en viktig källa tillmineraler för individer som inte får i sig tillräckligt med mineraler via kosten. Det gårdock i nuläget inte att fastställa betydelsen av dricksvatten som en mineralkälla förindivider som äter en mineralrik kost.

  • 34.
    Berntsson, Annika
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    De Vleeschouwer, Francois
    Bertrand, Sebastien
    Late Holocene high precipitation events recorded in lake sediments and catchment geomorphology, Lake Vuoksjavratje, NW Sweden2015In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 44, no 4, 676-692 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we show the potential of combining multi-proxy analysis of lake sediments with catchment geomorphology to better understand palaeoenvironmental changes. Previous studies have suggested that alpine lakes in N Sweden may be highly sensitive to variations in catchment erosion and precipitation, and that this sensitivity may influence ecologically based reconstructions of past temperature changes. We analysed lake sediments covering the last 5100 years from the alpine Lake Vuoksjavratje in NW Sweden in order to identify different erosional regimes in the lake catchment, sediment sources and lake sedimentary processes, which ultimately affect the palaeoecological record. The measured proxies include elemental geochemistry from XRF core scanning, grain size, sediment accumulation rates, fraction of terrestrial organic carbon and geomorphological mapping, supported by previously published chironomid and total organic carbon data. From the integrated results we identified time intervals when increased intensity of precipitation altered sedimentation and lake catchment erosional processes. The most prominent event occurred c. 2900 cal. a BP and is interpreted to be the result of excessive precipitation, possibly related to the climatic shift towards cooler and wetter conditions referred to as the 2.8 ka event.

  • 35.
    Beygi, Heydar
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Impact of irrigation development and climate change on the water level of Lake Urmia, Iran2015Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Lake Urmia, located in the north-west of Iran, is one of the largest hypersaline lakes in the world. In recent years, there has been a significant decrease in the lake’s area and volume by 88% and 80% respectively. An integrated water balance model of the Lake Urmia Drainage Basin (LUDB) and Lake Urmia was developed to identify these main drivers of the significant changes, and to investigate the possible future evolution of the lake under effects of projected climate change and land use change. We used an energy balance method to estimate the evaporation from the lake and the Turc-Langbein method to estimate the evapotranspiration from the drainage basin of the lake. Agricultural irrigation water was introduced to the model as an extra precipitation over the irrigated fields, after being subtracted from the surplus runoff (precipitation−evapotranspiration). The agricultural land development was assumed to be linear that changed from 300000 ha at 1979 to 500000 at 2010, which is consistent with the best available data on the actual irrigation development in the basin. We estimated the annual evaporation over the Lake Urmia and the evapotranspiration over its drainage basin as 932 mm and 287 mm respectively. Our results showed that decreased precipitation and increased temperature over the basin since 1995 could explain 68% of the observed lake level decrease. Irrigation developments during the last four decades were found to be responsible for 32% of the observed lake level decrease. Thus the future lake level of the Lake Urmia is very likely to continue to decrease unless the current climate condition will be followed by a period of increased precipitation. If the current climate conditions will prevail also in the future, even a 20% decrease in the irrigated land area, which is actually quite ambitious, will not make the lake recover to its ecological level at the end of 2020.

  • 36. Björk, Alexandra
    et al.
    Skånes, Helle
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The Need for Awareness of Semantic Plasticity in International Harmonization of Geographical Information: Seen from a Nordic Forest Classification Perspective2015In: Land Use and Land Cover Semantics: Principles, Best Practices and Prospects / [ed] Ola Ahlqvist, Dalia Varanka, Steffen Fritz, Krzysztof Janowicz, Boka Raton: CRC Press, 2015, 41-58 p.Chapter in book (Refereed)
    Abstract [en]

    The aim of this chapter is to address and clarify the important issues and challenges of semantic plasticity when it comes to forest classification and geographical information. Necessary improvements for international data harmonization and implementation are highlighted along with the need for increased awareness of the consequences for ecological modeling. We envisage a combination of thoroughly described metadata and controlled vocabularies as a means to ensure the future use of a wide range of regional and national classification systems in an ontological framework that enables crosswalks between classification systems and spatial comparisons between existing data sets. This would allow for a wide range of old, contemporary, and future data sets to be used together in landscape-related analyses.

  • 37. Björk, Alexandra
    et al.
    Skånes, Helle
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ahlqvist, Ola
    Ser vi skogen för alla träd?: Vikten av semantisk plasticitet vid harmonisering av geodata2015In: SINUS, no 4, 2 p.Article in journal (Other (popular science, discussion, etc.))
  • 38.
    Blomberg, Freddy
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Inläckage i dagbrott: En jämförelse mellan beräknade och uppmätta värden i dagbrott i norra Sverige2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Before the construction of an open pit mine is initialized it is common practice to perform hydrogeological surveys, in order to quantify the inflow of groundwater from surrounding soil and bedrock layers. As expansion of the pits progress, continuous pumping will need to be done, as groundwater will otherwise fill the pits, preventing further mining. Several quantification methods are available for these analyses, which can be either analytical or numerical in their structure. In this study, a review of established methods is performed. Then the inflow to five active mines in northern Sweden are estimated, using four analytical methods. The results from using these methods are then compared to the measured pumping rates in the mines, to evaluate the methods efficiency in estimating the correct withdrawal. One of the mines is also evaluated using a numerical model. All methods approximate the inflow rates to the same order of magnitude as the measured values. However, the same method can in some mines overestimate the inflow while in other mines make an underestimation of it. As they in most cases make an adequate approximation of the inflow, further use of the methods are recommended. Smaller adjustments might be needed based on local knowledge of the modeled area. The sensitivity analysis that was performed show a significant predisposition toward changes in hydraulic conductivity, emphasizing the importance of thorough surveys before parameterization of the models.

  • 39.
    Blomdin, Robin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Paleoglaciology of the Tian Shan and Altai Mountains, Central Asia2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The mountain-systems of Central Asia, act as barriers to atmospheric circulation patterns, which in turn impose striking climate gradients across the region. Glaciers are sensitive indicators of climate change and respond to changes in climate gradients over time by advancing during cold and wet periods and receding during warm and dry periods. The aim of this thesis is to investigate whether there are large-scale patterns in how past glaciers in the Tian Shan and the Altai Mountains of Central Asia responded to climate change. Multiple methods have been used, including: remote sensing, terrain analysis, field investigations, and cosmogenic nuclide (CN) dating. The glacial landform records indicate that the region experienced mainly alpine-style glaciations in the past. Large complexes of ice-marginal moraines in high elevation basins are evidence of outlet glaciers sourced from large valley glaciers, ice caps and ice-fields, and these moraine sequences, record the maximum extent of paleoglaciation. In the Ikh-Turgen Mountains, located in the continental, eastern Altai Mountains, deglaciation of these moraines occurred during marine oxygen isotope stage (MIS) 3 at ~45 ka. This is consistent with a colder and wetter climate during this time, inferred from ice core and lake level proxies. Another deglacial phase occurred during MIS 2 at ~23 ka, synchronous with the global Last Glacial Maximum. In the Russian Altai Mountains, lobate moraines in the Chuya Basin indicate deglaciation at ~19 ka, by a highly dynamic paleoglacier in the Chagan-Uzun catchment, which experienced surge-like behaviour. Furthermore, across the Tian Shan, an evaluation of new and existing CN glacial chronologies (25 dated moraines) indicates that only one regional glacial stage, between 15 and 28 ka (MIS 2), can be defined and spatially correlated across the region. These paleoglaciers were mainly restricted to valleys as a result of arid conditions during this time and variation in their extents is interpreted to reflect topographic modulation on regional climate. The ages of the oldest evidence for robust local glacial stages in the Tian Shan are not yet well constrained, however, moraines in the central Kyrgyz Tian Shan and the eastern Chinese Tian Shan have apparent minimum ages overlapping with MIS 5 and MIS 3 (with missing MIS 4 and 6 stages). However, different geological processes, such as inheritance and post-depositional shielding (e.g. deposition by surging glaciers or hummocky terrain deposition), have influenced the dating resolution, making several moraine ages inappropriate for regional comparison. Finally, to quantify regional patterns of paleoglaciation, the hypsometry (area-elevation distribution) of glacial landforms is used to estimate average paleo equilibrium line altitudes for the region. This analysis shows that while present-day ELAs mirror strong climate gradients, paleoglaciation patterns were characterised by more gentle ELA gradients. The paleo-ELA depressions across Central Asia were most prominent in the continental southern and eastern regions (500–700 m). Finally, the results from this thesis, show that Central Asia was repeatedly glaciated in the past, but underscore the importance of considering 1) catchment characteristics and styles of glaciation and 2) other non-climatic factors controlling glacier dynamics when interpreting CN chronologies to make paleoclimate inference.

  • 40.
    Blomdin, Robin
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University.
    The Late Glacial History of the Magellan Strait in southern Patagonia, Chile: Testing the Applicability of KF-IRSL Dating2012Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The timing of the ice margin retreat of the Late Glacial Patagonian ice sheet (PIS) in southern Patagonia has been the object of discussion for many years. In order to resolve questions about the complex response of the PIS to past climate change; geological interpretation and modelling data needs evaluation against absolute chronology. The aim of this project is to re-map the landforms and sediment of the Magellan Strait, to reconstruct the late glacial ice retreat during the deglaciation and to investigate the applicability of OSL dating to glaciofluvial sediment from this region. Unfortunately previous studies have shown that the quartz OSL luminescence characteristics, of this region, are unsuitable for dating. Therefore the potential of K-feldspar IRSL signals are reviewed and examined. Samples were collected from landforms interpreted as being deposited during the deglaciation of the Magellan ice lobe, with an expected age range between 17.5 and 23 ka, and from recently deposited sediments (<1 ka). Small aliquots and single grain distributions were studied by applying a IR50 SAR protocol with IRSL stimulation at 50°C for 100 s and a preheat of 250 °C (held at 60 s) are measured.  Appropriate uncertainties were assigned to the dose distribution data, by quantifying the laboratory over-dispersion (σOD) parameter (22.2% for small aliquots and 17.7 % for single grains) in laboratory bleached and γ-irradiated samples.  Thereafter the possible effects of incomplete bleaching and anomalous fading were examined. For the natural samples environmental over-dispersions between 30–130 % and mean interpreted residual doses between ~30 and 80 Gy were observed. Statistical models were further applied to identify the part of the dose population that was most likely to have been completely bleached. The models are consistent with each other which imply that they successfully identified the fully-bleached grains in the distributions; however observed discrepancies between the small aliquot and single grain data were also discussed. Large g2day values (on average 7.92±0.6%/decade for large aliquots) were observed but nevertheless, comparing our fading corrected ages to the expected age range result in 2 out of 3 ages consistent with geological interpretation and an established radiocarbon and cosmogenic nuclide chronology suggesting that this correction was done successfully. The results of these investigations suggest that small aliquot/single grain fading can be corrected for using an average value and that KF-IRSL dating is applicable in this part of Southern Patagonia. The third age is supported by an alternative geological interpretation while the two consistent ages imply that in the Magellan Strait the hills of the Brunswick peninsula (70-100 m.a.s.l) were deglaciated at around ~21 ka. Finally some recommendations for future research are considered.

  • 41.
    Blomdin, Robin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Purdue University, USA.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harbor, Jon M.
    Stockholm University, Faculty of Science, Department of Physical Geography. Purdue University, USA.
    Lifton, N. A.
    Heyman, J.
    Gribenski, Natacha
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Petrakov, D. A.
    Caffee, M. W.
    Ivanov, M. N.
    Hättestrand, Clas
    Stockholm Univ, Dept Phys Geog, Geomorphol & Glaciol, Stockholm, Sweden.
    Rogozhina, I.
    Usubaliev, R.
    Evaluating the timing of former glacier expansions in the Tian Shan: A key step towards robust spatial correlations2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 153, 78-96 p.Article in journal (Refereed)
    Abstract [en]

    The timing of past glaciation across the Tian Shan provides a proxy for past climate change in this critical area. Correlating glacial stages across the region is difficult but cosmogenic exposure ages have considerable potential. A drawback is the large observed scatter in Be-10 surface exposure data. To quantify the robustness of the dating, we compile, recalculate, and perform statistical analyses on sets of 10Be surface exposure ages from 25 moraines, consisting of 114 new and previously published ages. We assess boulder age scatter by dividing boulder groups into quality classes and rejecting boulder groups of poor quality. This allows us to distinguish and correlate robustly dated glacier limits, resulting in a more conservative chronology than advanced in previous publications. Our analysis shows that only one regional glacial stage can be reliably correlated across the Tian Shan, with glacier expansions occurring between 15 and 281 a during marine oxygen isotope stage (MIS) 2. However, there are examples of older more extensive indicators of glacial stages between MIS 3 and MIS 6. Paleoglacier extent during MIS 2 was mainly restricted to valley glaciation. Local deviations occur: in the central Kyrgyz Tian Shan paleoglaciers were more extensive and we propose that the topographic context explains this pattern. Correlation between glacial stages prior to late MIS 2 is less reliable, because of the low number of samples and/or the poor resolution of the dating. With the current resolution and spatial coverage of robustly-dated glacier limits we advise that paleoclimatic implications for the Tian Shan glacial chronology beyond MIS 2 are speculative and that continued work toward robust glacial chronologies is needed to resolve questions regarding drivers of past glaciation in the Tian Shan and Central Asia.

  • 42.
    Blomdin, Robin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harbor, Jonathan M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gribenski, Natacha
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Caffee, Marc W.
    Heyman, Jakob
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rogozhina, Irina
    Ivanov, Mikhail N.
    Petrakov, Dmitry A.
    Walther, Michael
    Rudoy, Alexei N.
    Zhang, Wei
    Orkhonselenge, Alexander
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lifton, Nathaniel A.
    Jansson, Krister N.
    Paleoglaciation on opposite flanks of the Ikh-Turgen Mountains, Central Asia: Importance of style of moraine deposition for 10-Be surface exposure datingManuscript (preprint) (Other academic)
    Abstract [en]

    The ages of marginal moraines that record extensive glacier expansions across the Altai Mountains of Central Asia are poorly documented. We present 18 10Be exposure ages from moraines in valleys on opposite flanks of the Ikh-Turgen Mountains. On the eastern side, exposure ages from a latero-frontal moraine indicate deglaciation during MIS 3 (45.3±2.7 ka) and MIS 2 (22.8±3.5 ka). Corresponding exposure ages, from the western side, indicate a more complex story with large scatter (~14-53 ka). Owing to their close proximity, the paleoglaciers should have responded similarly to climate forcing, yet they exhibited a distinctly different behavior. We propose that differences in glacier dynamics caused differences in ice-marginal depositional environments, explaining the scatter in exposure ages on the western side. This study shows the importance of style of deposition in chronological studies of glacial landforms and demonstrates that certain moraine types can be difficult to use as paleoclimate proxies.

  • 43.
    Blomdin, Robin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harbor, Jonathan M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Heyman, Jakob
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gribenski, Natacha
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Topographic and climatic controls on paleoglaciation patterns across the Tian Shan and Altai Mountains, Central AsiaManuscript (preprint) (Other academic)
    Abstract [en]

    Reconstructing spatial patterns of the extents and dynamics of paleoglaciers across Central Asia is key in understanding the mechanisms of global environmental change. The Tian Shan and Altai Mountains are located in the continental interior of Eurasia, at the confluence of several major climate systems. In order to test hypothesized patterns in paleoglacier extent, and to test the role of paleoclimate and mountain topography in modulating the evolution of these glacial systems, we perform a domain-wide terrain analysis. We first divide the Tian Shan and the Altai Mountains into six physiographic regions delineated by major drainage divides and outlining generalised climate zones. Thereafter we mine published datasets on the distribution of glaciers and glacial landforms, calculate their area-elevation distributions (hypsometry), and extract present-day regional equilibrium line altitudes (ELAs) and long-term average ELAs (paleo-ELAs). We show that the use of glacial landform hypsometry is an effective tool to quantify broad-scale paleoglaciation patterns and find that there is a regional variability in glacier extents across the Tian Shan and Altai Mountains. Reconstructed ELAs show pronounced spatial gradients; increasing ELAs from northern to southern Tian Shan, and increasing ELAs from the northern to both the southeastern and southwestern Altai Mountains. In contrast, maximum paleoglaciation patterns and paleo-ELAs were more uniform across the two mountain systems, with inter-regional topographic variability influencing moraine distributions and thus complicating regional paleo-ELA determinations. Because estimated paleo-ELAs were relatively uniform across the Tian Shan and Altai Mountains, the paleo-ELA lowering were most pronounced in the more continental southern and eastern regions. Our current data is insufficient to explain whether this observation is the result of a different regional paleoclimatic regime than today, or if paleoglaciers responded dynamically different to a paleoclimate forcing of the same magnitude. Our ELA reconstructions also lack temporal constraints, so we furthermore propose that future studies systematically compare hypsometry-derived ELA reconstructions with those stemming from surface energy mass balance models, other proxy records (i.e. lake- and ice core records), and from chronologically constrained ice-marginal moraines.  

  • 44.
    Blomdin, Robin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harbor, Jonathan M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lifton, Nathaniel A.
    Heyman, Jakob
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gribenski, Natacha
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Petrakov, Dmitry A.
    Caffee, Marc W.
    Ivanov, Mikhail N.
    Hättestrand, Clas
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rogozhina, Irina
    Usubaliev, Ryskul
    Evaluating the timing of former glacier expansions in the Tian Shan: a key step towards robust spatial correlationsIn: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457XArticle in journal (Refereed)
    Abstract [en]

    The timing of past glaciation across the Tian Shan provides a proxy for past climate change in this critical area. Correlating glacial stages across the region is difficult but cosmogenic exposure ages have considerable potential. A drawback is the large observed scatter in 10Be surface exposure data. To quantify the robustness of the dating, we compile, recalculate, and perform statistical analyses on sets of 10Be surface exposure ages from 25 moraines, consisting of 114 new and previously published ages. We assess boulder age scatter by dividing boulder groups into quality classes and rejecting boulder groups of poor quality. This allows us to distinguish and correlate robustly dated glacier limits, resulting in a more conservative chronology than advanced in previous publications. Our analysis shows that only one regional glacial stage can be reliably correlated across the Tian Shan, with glacier expansions occurring between 15 and 28 ka during marine oxygen isotope stage (MIS) 2. However, there are examples of older more extensive indicators of glacial stages between MIS 3 and MIS 6. Paleoglacier extent during MIS 2 was mainly restricted to valley glaciation. Local deviations occur: in the central Kyrgyz Tian Shan paleoglaciers were more extensive and we propose that the topographic context explains this pattern. Correlation between glacial stages prior to late MIS 2 is less reliable, because of the low number of samples and/or the poor resolution of the dating. With the current resolution and spatial coverage of robustly-dated glacier limits we advise that paleoclimatic implications for the Tian Shan glacial chronology beyond MIS 2 are speculative and that continued work toward robust glacial chronologies is needed to resolve questions regarding drivers of past glaciation in the Tian Shan and Central Asia. 

  • 45.
    Bohman, Ida
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Den arktiska permafrostens minskning och dess positiva feedback till den globala uppvärmningen2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    24 % of the Northern Hemisphere’s landmass is underlain by permafrost. 1 700 billion tonnes of organic carbon (C) is stored in the permafrost, and the ongoing climate change lead to permafrost thawing and carbon release.

    This study examines the extent of thawing permafrost and the estimated carbon emissions as a consequence of permafrost thawing. The results show an estimated decrease of near-surface permafrost up to 81% before 2100 due to an increase of the average global temperature. Thawing permafrost releases CO2 and CH4 to the atmosphere, which amplifies the greenhouse effect and creates a positive feedback to global warming.

    The magnitude of the positive feedback is uncertain but an average of 178 Pg C is expected to release to the atmosphere by 2100 if the anthropogenic emissions continues. A potential increase in biomass due to favorable growing conditions is not expected to offset the carbon emissions.

  • 46. Bokhorst, Stef
    et al.
    Pedersen, Stine Hojlund
    Brucker, Ludovic
    Anisimov, Oleg
    Bjerke, Jarle W.
    Brown, Ross D.
    Ehrich, Dorothee
    Essery, Richard L. H.
    Heilig, Achim
    Ingvander, Susanne
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Johansson, Cecilia
    Johansson, Margareta
    Jonsdottir, Ingibjorg Svala
    Inga, Niila
    Luojus, Kari
    Macelloni, Giovanni
    Mariash, Heather
    McLennan, Donald
    Rosqvist, Gunhild Ninis
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Bergen, Norway.
    Sato, Atsushi
    Savela, Hannele
    Schneebeli, Martin
    Sokolov, Aleksandr
    Sokratov, Sergey A.
    Terzago, Silvia
    Vikhamar-Schuler, Dagrun
    Williamson, Scott
    Qiu, Yubao
    Callaghan, Terry V.
    Changing Arctic snow cover: A review of recent developments and assessment of future needs for observations, modelling, and impacts2016In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 45, no 5, 516-537 p.Article, review/survey (Refereed)
    Abstract [en]

    Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.

  • 47. Bothe, Oliver
    et al.
    Hind, Alistair
    Stockholm University, Faculty of Science, Department of Physical Geography. Stockholm University, Faculty of Science, Department of Mathematics.
    Moberg, Anders
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zorita, Eduardo
    Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium2015In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, no 12, 1673-1699 p.Article in journal (Refereed)
    Abstract [en]

    Estimated external radiative forcings, model results, and proxy-based climate reconstructions have been used over the past several decades to improve our understanding of the mechanisms underlying observed climate variability and change over the past millennium. Here, the recent set of temperature reconstructions at the continental-scale generated by the PAGES 2k project and a collection of state-of-the-art model simulations driven by realistic external forcings are jointly analysed. The first aim is to estimate the consistency between model results and reconstructions for each continental-scale region over the time and frequency domains. Secondly, the links between regions are investigated to determine whether reconstructed global-scale covariability patterns are similar to those identified in model simulations. The third aim is to assess the role of external forcings in the observed temperature variations. From a large set of analyses, we conclude that models are in relatively good agreement with temperature reconstructions for Northern Hemisphere regions, particularly in the Arctic. This is likely due to the relatively large amplitude of the externally forced response across northern and high-latitude regions, which results in a clearly detectable signature in both reconstructions and simulations. Conversely, models disagree strongly with the reconstructions in the Southern Hemisphere. Furthermore, the simulations are more regionally coherent than the reconstructions, perhaps due to an underestimation of the magnitude of internal variability in models or to an overestimation of the response to the external forcing in the Southern Hemisphere. Part of the disagreement might also reflect large uncertainties in the reconstructions, specifically in some Southern Hemisphere regions, which are based on fewer palaeoclimate records than in the Northern Hemisphere.

  • 48.
    Boyd, Meighan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Speleothems from Warm Climates: Holocene Records from the Caribbean and Mediterranean Regions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis contributes to increased knowledge on Holocene climate and environmental variability from two complex and sparsely studied areas. Using a speleothem from Gasparee Cave, Trinidad, as a paleoclimate archive, the local expression of the 8.2 ka (thousand years before 1950) climate event and associated patterns of the inter-tropical convergence zone (ITCZ) and rainfall is provided. Subsequent speleothem studies using multi-proxy analysis of stalagmites from Kapsia Cave and Alepotrypa Cave, Greece, provide records of climate, vegetation and human induced changes in the cave environment during parts of the Holocene.

    The speleothems from the well-studied Neolithic habitation site, Alepotrypa Cave, have produced a climate and habitation record which covers the period of 6.3-1.0 ka. The cave was inhabited between 8.0-5.2 ka and was closed by a tectonic event, which has preserved the settlement. The stable oxygen record shows the first well-dated and robust expression of the 4.2 ka dry event in the Peloponnese, places the timing of the 3.2 ka dry event within an ongoing dry period, and shows a final dry event at 1.6 ka. The North Atlantic as well as more regional drivers, such as the North Sea Caspian Pattern Index is proposed to, in a complex interplay, govern many of the climate trends and events observed.

    Trace element variation after the site is abandoned indicate what is interpreted as two volcanic eruptions, the Minoan eruption of Thera (Santorini) around 3.6 ka and the 2.7 ka eruption of Somma (Vesuvius). Variations in trace elements during the habitation period show clear human influence, indicating an association with specific cave activities. One of the most interesting prospects for continued work on Alepotrypa Cave is this successful marriage of speleothem studies and archeology. A framework of dates which constrain some behavior of people living in the cave is only the beginning, and there is great potential to continue finding new clues in the speleothem data.

  • 49.
    Boyd, Meighan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hoffmann, Dirk
    Max Planck Institute for Evolutionary Anthropology, Germany.
    Jochum, Klaus Peter
    Max Planck Institute for Chemistry, Germany.
    Karkanas, Panagiotis
    American School of Classical Studies at Athens, Greece.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Papathanasiou, Anastasia
    Greek Ministry of Culture, Greece.
    Scholz, Denis
    Johannes Gutenberg-University Mainz, Germany.
    Stoll, Brigitte
    Max Planck Institute for Chemistry, Germany.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Trace elements as recorders of human activity and environmental indicators at Alepotrypa Cave, GreeceManuscript (preprint) (Other academic)
  • 50.
    Boyd, Meighan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Speleothems from Alepotrypa Cave: Towards climate reconstruction2015In: Alepotrypa Cave in the Mani, Greece: A festschrift to honor Dr. G. Papathanasopoulos on the occasion of his 90th birthday / [ed] Α. Papathanasiou, M. Galaty, P. Karkanas, W. Parkinson, D. Pullen, Oxford: Oxbow Books, 2015Chapter in book (Other academic)
1234567 1 - 50 of 481
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