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  • 1.
    Abbasova, Tahira
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Detection and analysis of changes in desertification in the Caspian Sea Region2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The Caspian Region includes the Caspian Sea and five littoral states: Azerbaijan, Iran, Turkmenistan, Kazakhstan and Russian. 40% of the Caspian coastal zone is arid, 69% of this territory undergone desertification according to international reports. Among the reasons are soil erosion caused by water, wind and irrigation, the salinization of soil, intense bioresources usage, and soil pollution due to oil extraction and production. Desertification is a serious problem, at global, national and local scales. It is important to know what should be sustained or developed in order to protect land from desertification. The generalization of data over desertification processes in Caspian countries, studying the dynamics of this process in space and time could help facilitate measures to counter regional desertification.

    To understand Caspian Region coastal desertification phenomenon, vegetation cover satellite images for the years 1982 – 2006 were investigated to give map vegetation changes over time. The Normalized Difference Vegetation Index (NDVI) data for this study was derived from the Global Inventory Modeling and Mapping Studies (GIMMS) dataset, with the spatial resolution of 8 km.

    A coastal strip 160 km from the coast, divided by countries, was investigated. Theanalyses were focused on extent and severity of vegetation cover degradation, and possible causes such as landscape, land use history and culture, climatic changes and policies. The aim was to address questions related to desertification phenomenon, by focusing on Caspian Region time-series of vegetation cover data and investigation patterns of desertification in the region.

    In this study evidence of land degradation in the Caspian Region countries was found to occur on local scales or sub-national scales rather than across the regional as a whole. Changes in vegetation cover revealed by AVHRR NDVI appeared to be reversible in character and were dependent on the climate conditions, and anthropogenic impact in approximately equal proportions.

  • 2. Abbott, P. M.
    et al.
    Austin, W. E. N.
    Davies, S. M.
    Pearce, N. J. G.
    Rasmussen, T. L.
    Wastegård, Stefan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Brendryen, J.
    Re-evaluation and extension of the Marine Isotope Stage 5 tephrostratigraphy of the Faroe Islands region: The cryptotephra record2014Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 409, s. 153-168Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Previous studies of marine sequences from the Faroe Islands region have identified a series of coarse-grained tephra horizons deposited during Marine Isotope Stage (MIS) 5. Here we reassess the MIS 5 tephrostratigraphy of the Faroe Islands region and focus on the cryptotephra deposits preserved within the fine-grained fraction of marine core LINK 16. We also extend the record to encompass the late MIS 6 and early MIS 4 periods. A density separation technique, commonly used for tephra investigations in lacustrine settings but rarely applied to marine sediments, is utilised to explore the fine-grained material and EPMA and LA-ICP-MS are employed to determine the major and trace element composition of individual tephra shards. In total, 3 basaltic and 3 rhyolitic Icelandic cryptotephra deposits with homogeneous geochemical compositions are identified - all of which have the potential to act as isochronous tie-lines. Geochemical results highlight that the Grimsvotn volcanic system of Iceland is the predominant source of the basaltic horizons and the Oraefajokull or Torfajokull systems are the likely sources of the rhyolitic deposits. Three of the horizons have been previously recognised in Faroe Islands region marine sequences, with two of these deposits traceable into a Norwegian Sea sequence. An early MIS 4 rhyolitic horizon is the most widespread deposit as it can be traced into the Norwegian Sea and to the south into a record from the Rockall Trough. Basaltic and rhyolitic horizons deposited during late MIS 6 have not been recognised in other sequences and represent new additions to the regional tephrostratigraphy.

  • 3. Abbott, Peter M.
    et al.
    Davies, Siwan M.
    Steffensen, Jorgen Peder
    Pearce, Nicholas J. G.
    Bigler, Matthias
    Johnsen, Sigfus J.
    Seierstad, Inger K.
    Svensson, Anders
    Wastegård, Stefan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    A detailed framework of Marine Isotope Stages 4 and 5 volcanic events recorded in two Greenland ice-cores2012Ingår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 36, s. 59-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sulphate records from Greenland ice-cores indicate that Marine Isotope Stages 4 and 5 were charactensed by a higher incidence of large volcanic eruptions than other periods during the last glacial period, however, few investigations have focused on tephra deposits associated with these volcanic eruptions and the nature and origin of the events. Here we present a detailed tephrochronological framework of the products of 15 volcanic events spanning this interval: the majority of which have been preserved as cryptotephra horizons within the Greenland records. The major element compositions of individual glass shards within these horizons indicate that 13 of the eruptions originated from Iceland and 6 of these events can be correlated to the specific volcanic systems of Katla, Grimsvotn, Grimsvotn-Kverkfjoll and either Reykjanes or Veidivotn-Bardarbunga. For the remaining Icelandic horizons a source from either the rift zone or a flank zone can be suggested based on rock suite affinities. Two horizons have been correlated to a source from the Jan Mayen volcanic system which represents the first discovery of material from this system within any Greenland ice-cores. The robust geochemical characterisations, independent ages for these horizons (derived from the GICCO5 ice-core chronology) and stratigraphic positions relative to the Dansgaard-Oeschger climate events recorded in the Greenland ice-cores represent a critical framework that provides new information on the frequency and nature of volcanic events occurring in the North Atlantic region during MIS 4 and 5. This framework can now be utilised in the assessment of the differential timing and rate of response to the millennial-scale climatic events that characterised this period, through the use of the tephra horizons as time-synchronous tie-lines to other palaeoclimatic sequences.

  • 4. Abbühl, Luca
    et al.
    Norton, Kevin
    Jansen, John
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Schlunegger, Fritz
    Aldahan, Ala
    Possnert, Göran
    Erosion rates and mechanisms of knickzone retreat inferred from Be-10 measured across strong climate gradients on the northern and central Andes Western Escarpment2011Ingår i: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 36, s. 1464-1473Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    escarpment edge, deep gorges and distinct knickzones in river profiles characterize the landscape on the Western Escarpment of the Andes between ~5°S and ~18°S (northern Peru to northern Chile). The Western Escarpment straddles strong north-south and east-west precipitation gradients, which we exploit in order to determine how climate affects denudation rates in three river basins spanning an otherwise relatively uniform geologic and geomorphologic setting. The Western Escarpment reflects an ongoing transient response to major tectonic perturbation in the Late Miocene when surface uplift created a steep ramp separating drainage systems above the growing escarpment from those below. Upstream of this ramp, and now forming the uplifted Meseta/Altiplano (~3000 m a.s.l.), streams remain graded to the Late Miocene base level constituted by a series of Tertiary volcanic-volcanoclastic rocks, Streams below the ramp have responded to the Late Miocene surface uplift by incising deeply into fractured Mesozoic rocks via a series of steep, headward retreating knickzones that grade to the present-day base level defined by the Pacific Ocean. 

    We find that the Tertiary units function as cap-rocks, which aid in the parallel retreat of the sharp escarpment edge and upper knickzone tips. Upstream of these knickzones, on the Meseta/Altiplano, 10Be-derived catchment denudation rates of the Rio Piura (5°S), Rio Pisco (13°S) and Rio Lluta (18°S) average ~10 mm ky–1 irrespective of precipitation rates; whereas, downstream of the escarpment edge, denudation rates range from 10 mm ky-1 to 250 mm ky-1 and correlate positively with precipitation rates, but show no significant correlation with hillslope angles or channel steepness. These relationships are explained by the presence of the cap-rock and climate-driven fluvial incision that steepens hillslopes to near-threshold conditions. In addition, valley width and the extent of dissection both appear to increase with increasing precipitation to the north, consistent with climate-forcing of landscape morphology in the deeply incised terrain beneath the escarpment edge.

    Since escarpment retreat and the precipitation pattern were established at least in the Miocene, we speculate that the present-day distribution of morphology and denudation rates has probably remained largely unchanged during the past several millions of years as the knickzones have propagated headward into the plateau.

  • 5.
    Adler, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Studier av geomorfologi på Mani, Peloponnesos, Grekland2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Halvön Mani i södra Peloponnesos, Grekland, ligger enbart 50 km från subduktionszonen Hellenic arc. Det medför att aktiva tektoniska processer påverkar geomorfologin. Genom fjärranalys, analys av digital terrängmodell samt genom ett fem dagars fältarbete har en del av södra halvöns geomorfologi studerats. Recenta processer som idag skapar landformer har identifierats. Av dessa är det främst kemisk vittring och tektonik som dominerar. Även relikta landformer studerades för att skapa en komplettare bild över området. Två stycken stenfält upptäcktes på en av uddarna, som troligen skapats innan udden lyfts upp till nivån den befinner sig idag. Ett konglomerat överlagrade kalkstenen i en av vikarna och vittnar om stora massrörelser som skett då markytan även här var lägre än idag. Ett pediment finns på den västra sidan av berget Sagias. Asymmetrin beror troligen på en kombination av tektonik och havsnivåförändringar.

  • 6.
    Aggemyr, Elsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Cousins, Sara A. O.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Landscape structure and land use history influence changes in island plant composition after 100 years2012Ingår i: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 39, nr 9, s. 1645-1656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aim We investigated how current and historical land use and landscape structure affect species richness and the processes of extinction, immigration and species turnover. Location The northern part of the Stockholm archipelago, Baltic Sea, Sweden. We resurveyed 27 islands ranging from 0.3 to 33 ha in area. Methods We compared current plant survey data, cadastral maps and aerial photographs with records obtained from a survey in 1908, using databases and a digital elevation model to examine changes in plant community dynamics in space and time. We examined the effects of local and landscape structure and land use changes on plant species dynamics by using stepwise regression in relation to eight local and three landscape variables. The eight local variables were area, relative age, shape, soil heterogeneity, bedrock ratio, number of houses, forest cover change, and grazing 100 years ago. The three landscape variables were distance to mainland, distance to closest island with a farm 100 years ago, and structural connectivity. Hanskis connectivity measure was modified to incorporate both connectivity and fragmentation. Results The investigated islands have undergone drastic changes, with increasing forest cover, habitation, and abandonment of grassland management. Although the total species richness increased by 31% and mean island area by 23%, we found no significant increase in species richness per unit area. Local variables explain past species richness (100 years ago), whereas both local and landscape variables explain current species richness, extinctions, immigrations and species turnover. Grazing that occurred 100 years ago still influences species richness, even though grazing management was abandoned several decades ago. The evidence clearly shows an increase in nitrophilous plant species, particularly among immigrant species. Main conclusions This study highlights the importance of including land use history when interpreting current patterns of species richness. Furthermore, local environment and landscape patterns affect important ecological processes such as immigration, extinction and species turnover, and hence should be included when assessing the impact of habitat fragmentation and land use change. We suggest that our modified structural connectivity measure can be applied to other types of landscapes to investigate the effects of fragmentation and habitat loss.

  • 7.
    Aggemyr, Elsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Cousins, Sara A. O.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Plant species richness and composition, changes over a 100 year period in the Swedish archipelago - a landscape study2010Ingår i: The Future of Biodiversity: Genes, Species, Ecosystems: 40th Anniversary Conference / [ed] Volkmar Wolters, Janine Groh, Franziska Peter, Rainer Waldhardt, Giessen: Justus Liebig University Giessen , 2010, s. 118-118Konferensbidrag (Refereegranskat)
  • 8.
    Aggemyr, Elsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Cousins, Sara A. O.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Revisiting 27 islands in the Stockholm archipelago after a century – the effect of land use change on species composition2010Konferensbidrag (Refereegranskat)
  • 9.
    Ahlgren, Sara
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Changes in size distribution of lakes in the Nadym catchment, northern Russia2012Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Because of climate change and resource development there is an ongoing increase in the attention directed towards high latitude areas. Over the last years, warming in the Arctic has accelerated quickly. The warming climate can possibly lead to thawing of ground ice, which in turn leads to alterations of the cryosphere. This can have a huge influence on the terrestrial hydrology of the Arctic and, more specifically, on the presence and distribution of lakes in arctic regions since both are coupled to subsurface ice. In this thesis data from remote sensing were used to look at the change in the size distribution of lakes for the Nadym catchment in northern Russia. The aim was to find out if there has been an increase or decrease in the number of lakes in the area over the past years. Results suggest that there were 229 lakes less (representing a 4% decrease) in 2007–2009 compared to 1987, indicating that lakes are slowly disappearing. Also, the total lake surface area decreased with 5%. Almost half of the lakes that disappeared (49%) can be found among the smallest lakes ranging between 10–20 ha. In the entire catchment this size class was also found to be the class with by far the highest number of lakes.

  • 10. Ahlkrona, J.
    et al.
    Kirchner, Nina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Lotstedt, P.
    Accuracy of the zeroth- and second-order shallow-ice approximation - numerical and theoretical results2013Ingår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 6, nr 6, s. 2135-2152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In ice sheet modelling, the shallow-ice approximation (SIA) and second-order shallow-ice approximation (SOSIA) schemes are approaches to approximate the solution of the full Stokes equations governing ice sheet dynamics. This is done by writing the solution to the full Stokes equations as an asymptotic expansion in the aspect ratio epsilon, i.e. the quotient between a characteristic height and a characteristic length of the ice sheet. SIA retains the zeroth-order terms and SOSIA the zeroth-, first-, and second-order terms in the expansion. Here, we evaluate the order of accuracy of SIA and SOSIA by numerically solving a two-dimensional model problem for different values of epsilon, and comparing the solutions with afinite element solution to the full Stokes equations obtained from Elmer/Ice. The SIA and SOSIA solutions are also derived analytically for the model problem. For decreasing epsilon, the computed errors in SIA and SOSIA decrease, but not always in the expected way. Moreover, they depend critically on a parameter introduced to avoid singularities in Glen's flow law in the ice model. This is because the assumptions behind the SIA and SOSIA neglect a thick, high-viscosity boundary layer near the ice surface. The sensitivity to the parameter is explained by the analytical solutions. As a verification of the comparison technique, the SIA and SOSIA solutions for a fluid with Newtonian rheology are compared to the solutions by Elmer/Ice, with results agreeing very well with theory.

  • 11. Ahlkrona, Josefin
    et al.
    Kirchner, Nina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Lötstedt, Per
    A numerical study of scaling relations for non-Newtonian thin film flows with applications in ice sheet modelling2013Ingår i: Quarterly Journal of Mechanics and Applied Mathematics, ISSN 0033-5614, E-ISSN 1464-3855, Vol. 66, nr 4, s. 417-435Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article treats the viscous, non-Newtonian thin-film flow of ice sheets, governed by the Stokes equations, and the modelling of ice sheets with asymptotic expansion of the analytical solutions in terms of the aspect ratio, which is a small parameter measuring the shallowness of an ice sheet. An asymptotic expansion requires scalings of the field variables with the aspect ratio. There are several, conflicting, scalings in the literature used both for deriving simplified models and for analysis. We use numerical solutions of the Stokes equations for varying aspect ratios in order to compute scaling relations. Our numerically obtained results are compared with three known theoretical scaling relations: the classical scalings behind the Shallow Ice Approximation, the scalings originally used to derive the so-called Blatter-Pattyn equations, and a non-uniform scaling which takes into account a high viscosity boundary layer close to the ice surface. We find that the latter of these theories is the most appropriate one since there is indeed a boundary layer close to the ice surface where scaling relations are different than further down in the ice. This boundary layer is thicker than anticipated and there is no distinct border with the inner layer for aspect ratios appropriate for ice sheets. This makes direct application of solutions obtained by matched asymptotic expansion problematic.

  • 12.
    Ahlqvist, Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Context Sensitive Transformation of Geographic Information2000Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This research is concerned with theoretical and methodological aspects of geographic information transformation between different user contexts. In this dissertation I present theories and methodological approaches that enable a context sensititve use and reuse of geographic data in geographic information systems.

    A primary motive for the reported research is that the patrons interested in answering environmental questions have increased in number and been diversified during the last 10-15 years. The interest from international, national and regional authorities together with multinational and national corporations embrace a range of spatial and temporal scales from global to local, and from many-year/-decade perspectives to real time applications. These differences in spatial and temporal detail will be expressed as rather different questions towards existing data. It is expected that geographic information systems will be able to integrate a large number of diverse data to answer current and future geographic questions and support spatial decision processes. However, there are still important deficiencies in contemporary theories and methods for geographic information integration

    Literature studies and preliminary experiments suggested that any transformation between different users’ contexts would change either the thematic, spatial or temporal detail, and the result would include some amount of semantic uncertainty. Consequently, the reported experiments are separated into studies of change in either spatial or thematic detail. The scope concerned with thematic detatil searched for approaches to represent indiscernibility between categories, and the scope concerned with spatial detail studied semantic effects caused by changing spatial granularity.

    The findings make several contributions to the current knowledge about transforming geographic information between users’ contexts. When changing the categorical resolution of a geographic dataset, it is possible to represent cases of indiscernibility using novel methods of rough classification described in the thesis. The use of rough classification methods together with manual landscape interpretations made it possible to evaluate semantic uncertainty in geographic data. Such evaluations of spatially aggregated geographic data sets show both predictable and non-predictable effects. and these effects may vary for different environmental variables.

    Development of methods that integrate crisp, fuzzy and rough data enables spatial decision support systems to consider various aspects of semantic uncertainty. By explicitly representing crisp, fuzzy and rough relations between datasets, a deeper semantic meaning is given to geographic databasses. The explicit representation of semantic relations is called a Geographic Concept Topology and is held as a viable tool for context transformation and full integration of geographic datasets.

  • 13. Ahmad, Nawaz
    et al.
    Wörman, Anders
    Sanchez-Vila, Xavier
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Bottacin-Busolin, Andrea
    Hellevang, Helge
    Injection of CO2-saturated brine in geological reservoir: A way to enhanced storage safety2016Ingår i: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 54, s. 129-144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Injection of free-phase supercritical CO2 into deep geological reservoirs is associated with risk of considerable return flows towards the land surface due to the buoyancy of CO2, which is lighter than the resident brine in the reservoir. Such upward movements can be avoided if CO2 is injected in the dissolved phase (CO2aq). In this work, injection of CO2-saturated brine in a subsurface carbonate reservoir was modelled. Physical and geochemical interactions of injected low-pH CO2-saturated brine with the carbonate minerals (calcite, dolomite and siderite) were investigated in the reactive transport modelling. CO2-saturated brine, being low in pH, showed high reactivity with the reservoir minerals, resulting in a significant mineral dissolution and CO2 conversion in reactions. Over the injection period of 10yr, up to 16% of the injected CO2 was found consumed in geochemical reactions. Sorption included in the transport analysis resulted in additional quantities of CO2 mass stored. However, for the considered carbonate minerals, the consumption of injected CO2aq was found mainly in the form of ionic trapping.

  • 14. Ahmad, Waqas
    et al.
    Fatima, Aamira
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Awan, Usman Khalid
    Anwar, Arif
    Analysis of long term meteorological trends in the middle and lower Indus Basin of Pakistan-A non-parametric statistical approach2014Ingår i: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 122, s. 282-291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Indus basin of Pakistan is vulnerable to climate change which would directly affect the livelihoods of poor people engaged in irrigated agriculture. The situation could be worse in middle and lower part of this basin which occupies 90% of the irrigated area. The objective of this research is to analyze the long term meteorological trends in the middle and lower parts of Indus basin of Pakistan. We used monthly data from 1971 to 2010 and applied non-parametric seasonal Kendal test for trend detection in combination with seasonal Kendall slope estimator to quantify the magnitude of trends. The meteorological parameters considered were mean maximum and mean minimum air temperature, and rainfall from 12 meteorological stations located in the study region. We examined the reliability and spatial integrity of data by mass-curve analysis and spatial correlation matrices, respectively. Analysis was performed for four seasons (spring-March to May, summer-June to August-fall-September to November and winter-December to February). The results show that max. temperature has an average increasing trend of magnitude +0.16, +0.03, 0.0 and +0.04 degrees C/decade during all the four seasons, respectively. The average trend of min. temperature during the four seasons also increases with magnitude of +0.29, +0.12, +0.36 and +0.36 degrees C/decade, respectively. Persistence of the increasing trend is more pronounced in the min. temperature as compared to the max. temperature on annual basis. Analysis of rainfall data has not shown any noteworthy trend during winter, fall and on annual basis. However during spring and summer season, the rainfall trends vary from -1.15 to +0.93 and -3.86 to +2.46 mm/decade, respectively. It is further revealed that rainfall trends during all seasons are statistically non-significant. Overall the study area is under a significant warming trend with no changes in rainfall.

  • 15.
    Ahmed, Moinuddin
    et al.
    Fed Urdu Univ Arts Sci & Technol, Dept Bot, Karachi 75300, Pakistan.
    Krusic, Paul J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Charpentier Ljungqvist, Fredrik
    Stockholms universitet, Humanistiska fakulteten, Historiska institutionen.
    Zorita, Eduardo
    PAGES 2k Consortium,
    Continental-scale temperature variability during the past two millennia2013Ingår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 6, nr 5, s. 339-346Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period ad 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.

  • 16.
    Al Kamil, Mohammed
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    SATS och Friskis & Svettis - Var och för vem?2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The aim of this study is to investigate where and why the fitness clubs, Sats and Friskis & Svettis in Stockholms county, choose to locate their facilities in certain places and which their primarily targetgroups are. Furthermore, the aim is to gain knowledge of people’s health status in areas where the facilities are located, in order to see if they are located where exercise is most needed. Interviews were conducted with members of the fitness clubs but also with non members, i.e. people who lived in areas with an absence of fitness facilities. Further interviews have been made with managers of the fitness clubs and with two political representatives. The other methods were mapping of the facilities inrelationship to different variables in ArcGIS and field observations. The results of this study show thatthe facilities are mostly located in the central of Stockholm and places where income levels,population density and amount of people working in an area are high. The facilities can also be foundwhere there are large flows of people, for example near commercial centers such as shopping malls.The fitness clubs do not primarily focus on establishing any facilities in places where exercise is mostneeded. The target groups for Friskis & Svettis were both younger and older people and those who wanted to pay a low membership fee while Sats target groups were people aged between 20-50 years and were willing to pay a high price for a membership. Based on price for a membership, availability and what the clubs offers, some people may get excluded from Sats and Friskis & Svettis. Those people mostly live in low status areas and if they eventually would become members of the clubs it would require cheap prices, culture-specific exercise forms and better proximity between the residenceand the facility. Finally, since both the fitness clubs and the political representative’s claims that people everywhere should have the possibility to exercise regardless of their income level and so on, there should be a better interaction between all the actors in order for the clubs to be available to allthe people.

  • 17. Alekseeva, I.
    et al.
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Schrum, C.
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Reconstruction of historic changes of the Aral Sea water budget and sea-groundwater interactions by a coupled 3D sea-ice-groundwater model2007Ingår i: Geophysical Research Abstracts, Vol. 9, 10629, 2007, 2007Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A 3D coupled sea-ice-groundwater model has been developed and applied for an estimation of the water balance and groundwater-seawater interactions in the shrinking Aral Sea. The model developed combines the complete 3D sea-ice hydrodynamics model ECOSMO, including a mass and energy conserving wetting and drying scheme, and a simple groundwater model based on changes in hydraulic gradient in response to the sea surface variability. During the simulation period 1979-1993, the model successfully reproduced the rapid Aral Sea level drop, surface area decrease, coastline position changes and salinization. Model predictions of evaporation and groundwater inflow were also consistent with independent estimations. Model results indicated that within the 15 years period of simulations the net groundwater inflow to the Aral Sea might have increased by 10% or more as a direct effect of the sea level lowering.

    Furthermore, model scenario tests were carried out to examine effects of salinity on sea hydrodynamics and to estimate non-linear feedbacks of the sea thermo- and hydrodynamics, air-sea turbulent fluxes and the sea water balance. It was shown that a neglect of salinity in the sea hydro- and thermo dynamics resulted in considerable differences in the Aral Sea winter thermal conditions, which in turn influenced the air-sea exchange in the following spring and summer. As a result, the zero salinity scenario predicted higher evaporation rates and an considerably accelerated sea level lowering by up to 2 cm/yr, in comparison with the basic model run. An indirect influence of the fresh groundwater inflow in terms of water balance has been identified as less significant, however it was shown that the fresh groundwater input could influence the Aral Sea salinity distribution considerably since 1990’s.

  • 18. Alekseeva, Irina
    et al.
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Schrum, Corinna
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Reproducing the Aral Sea water budget and sea-groundwater dynamics between 1979 and 1993 using a coupled 3-D sea-ice-groundwater model2009Ingår i: Journal of Marine Systems, Vol. 76, nr 3, s. 296-309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have developed the 3-D sea-ice model, ECOSMO, into a coupled sea-ice–groundwater model and investigated the factors that may have influenced the groundwater–seawater interactions and the water balance of the shrinking Aral Sea. During the simulation period, 1979–1993, the model successfully reproduced the rapid Aral Sea level drop, surface area decrease, coastline position changes and increasing salinization of the Aral Sea. Model predictions of evaporation and groundwater inflow were also consistent with independent estimations. Model results indicated that the net groundwater inflow to the Aral Sea may have increased by 10% or more as a direct effect of the sea level lowering. Furthermore, model scenario tests showed that in comparison with a basic scenario, in which salinity effects were accounted for, not accounting for such effects resulted in considerable changes in ice formation and winter thermal conditions, which in turn influenced the thermo- and hydrodynamics and fresh water air-sea fluxes in the Aral Sea. As a result, the zero-salinity scenario predicted higher evaporation rates and an accelerated sea level lowering by up to 2 cm/yr, in comparison with the basic scenario. Model results showed that increased groundwater inflow to the sea may have influenced the Aral Sea salinity distribution since the 1990's. Our results emphasise the importance of taking into account both baroclinic hydrodynamics, sea-ice dynamics and as well as potentially increased future groundwater-related salinity effects in order to accurately estimate the Aral Sea water balance. More generally, models that can handle such highly dynamic systems may have a realistic potential for making detailed assessments of sea characteristics under the influence of climate and hydrological cycle changes.

  • 19.
    Alexanderson, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Brattforsheden: Vad sanden kan berätta om dess historia2007Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 20.
    Alexanderson, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Optiskt stimulerad luminiscensdatering (OSL) av nedisningshistorien i södra och mellersta Sverige2008Ingår i: SGU-rapport 2008-9: FoU-seminarium vid SGU 4 mars 2008 Dokumentation, 2008, s. 40-Konferensbidrag (Övrigt vetenskapligt)
  • 21.
    Alexanderson, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Residual OSL signals from modern Greenlandic river sediments2007Ingår i: Geochronometria, ISSN 1897-1695, Vol. 26, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ripple-laminated sandy deposits at shallow water depths in four rivers on Jameson Land, East Greenland were sampled for optically stimulated luminescence (OSL) dating. Silt-sized grains have significantly higher equivalent doses (~1.1 Gy) than sand grains (~0.1 Gy). This suggests that coarse grain-size fractions are better bleached and more suitable than fine grains for OSL dating of glaciofluvial/fluvial sediments. A sample from a sidebar deposited during the spring flood yielded 1.0 Gy (~500 years) while a subaerial deposit was completely zeroed. The spring flood deposit is considered to be most similar to deglacial conditions and incomplete bleaching of this amount (1 Gy) is generally not a significant source of error for sediments of Pleistocene age. Most samples have rather poor luminescence characteristics and are affected by thermal transfer if preheat temperatures at or above 260°C are used.

  • 22.
    Alexanderson, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Sub-till glaciofluvial sediments at Hultsfred, South Swedish Upland2010Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 132, nr 3&4, s. 153-159Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a gravel pit near Hultsfred, at the eastern margin of the South Swedish Upland, gravelly, sandy and silty-sandy beds covered by a thick, strati?ed gravelly diamicton are exposed. Large folds and shear-planes indicate post-depositional deformation of the sorted sediments, which according to OSL dating have a maximum Middle Weichselian (,60 ka) age. The sand and gravel are interpreted as glacio?uvial sediments that were deposited laterally during a Middle Weichselian deglaciation, or possibly subglacially during the Late Weichselian. The large-scale deformation was due to glaciotectonics, caused by an overriding wet-based ice sheet during the last deglaciation. The subglacial hydrostatical pressure was high and led to the formation of downward-injected clastic dykes. A basal till, which forms the cover moraine in the area, caps the succession. The fairly frequent occurrence of sub-till sediments on the South Swedish Upland demonstrates the limited effect of glacial erosion in parts of this area. During the Last Glacial Maximum, the South Swedish Upland was an ‘island’ of slow-moving, polythermal and at least partly non-erosive ice, surrounded by faster ice-streams in the Baltic and in the Skagerrak. The ice sheet may have left its main impact on the landscape during short periods during advance and deglaciation only.

  • 23.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Eskola, Kari O
    Helmens, Karin F
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Optical dating of a Late Quaternary sediment sequence from Sokli, northern Finland2008Ingår i: Geochronometria, Vol. 32, s. 51-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interstadial and non-glacial stadial sediments collected in boreholes from Sokli in northeastern Finland have been dated by optically stimulated luminescence on quartz and feldspar grains. The quartz OSL ages follow stratigraphic order, with one exception, and support the litho- and biostratigraphical correlation with the NW European mainland climate-stratigraphy and the marine oxygen-isotope stages. Feldspar IRSL dates generally overestimate the age, probably due to incomplete bleaching.

    The data show that during the last glacial cycle northeastern Finland was not glaciated until MIS 5b, around 90 ka. Interstadial conditions occurred around ~94 ka (MIS 5c), ~74-80 ka (MIS 5a) and 42-54 ka (MIS 3).

    The OSL ages have large standard errors mainly due to small sample sizes, relatively poor luminescence characteristics and uncertainties in dose-rate determinations.

  • 24.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Henriksen, Mona
    Landvik, Jon Y
    Ryen, Heidi T
    Chronologies of the glacial history of Svalbard – a review2010Ingår i: Arctic Palaeoclimate and its Extremes (APEX) abstract volume, 2010, s. 21-21Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The basis of the glacial history of Svalbard lies in stratigraphic studies of terrestrial and marine geological records. Classic litho- and biostratigraphy give us local relative chronologies of events but to compare with other areas and records we are dependent on absolute age control.

     

    This presentation will focus on the Middle to Late Quaternary terrestrial record to which a range of different absolute dating techniques have been applied; these techniques all have their pros and cons regarding materials, resolution, age range, etc. Amino acid chronology, although not a strictly absolute dating method, may provide some age inferences. Radiocarbon dating of organic material such as shell and bone is still the most common technique and one that is generally considered reliable. It is however limited by its age range to the last ~50 ka, and our interest goes further back than so. Various versions of luminescence dating, particularly optically stimulated luminescence (OSL), have therefore become strong contenders during the recent decade, mainly due to their longer age range and applicability to a wider range of deposits than radiocarbon dating. Luminescence dating nevertheless has its drawbacks too, for Svalbard these are mainly related to the risk of incomplete bleaching (leading to age overestimation) and poor resolution (leading to large uncertainties for final ages). Other techniques that have been used on fossil material include electron spin resonance (ESR) and uranium-thorium (U/Th) dating. In common for most techniques is that we cannot date glacial events, but the intervening non-glacial (interstadial, interglacial) episodes. Cosmogenic exposure dating is an exception, which is also able to provide information on the thickness of ice sheets through time.

     

    From a geologist’s point of view we will discuss these different techniques, their usefulness and what we can expect of them. Do the dating methods meet our wishes regarding resolution? Are results from different methods comparable? The discussion will be based on our experience from the ongoing SciencePub project (www.ngu.no/sciencepub) and on literature and we will show examples of method applications and comparisons.

  • 25.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Håkansson, Lena
    Dating the glacial history of northeast Greenland2007Ingår i: First Conference on Arctic Palaeoclimate and its Extremes, 2007Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 26.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Johnsen, Timothy
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Murray, Andrew S.
    Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, Aarhus University Risø DTU, DK-4000 Roskilde, Denmark .
    Re-dating the Pilgrimstad Interstadial with OSL: a warmer climate and a smaller ice sheet during the Swedish Middle Weichselian (MIS 3)?2010Ingår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 39, nr 2, s. 367-376Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pilgrimstad in central Sweden is an important locality for reconstructing environmental changes during the last glacial period (the Weichselian). Its central location has implications for the Scandinavian Ice Sheet as a whole. The site has been assigned an Early Weichselian age (marine isotope stage (MIS) 5 a/c; >74 ka), based on pollen stratigraphic correlations with type sections in continental Europe, but the few absolute dating attempts so far have given uncertain results. We re-excavated the site and collected 10 samples for optically stimulated luminescence (OSL) dating from mineral- and organic-rich sediments within the new Pilgrimstad section. Single aliquots of quartz were analysed using a post-IR blue single aliquot regenerative-dose (SAR) protocol. Dose recovery tests were satisfactory and OSL ages are internally consistent. All, except one from an underlying unit that is older, lie in the range 52–36 ka, which places the interstadial sediments in the Middle Weichselian (MIS 3); this is compatible with existing radiocarbon ages, including two measured with accelerator mass spectrometry (AMS). The mean of the OSL ages is 44±6 ka (n=9). The OSL ages cannot be assigned to the Early Weichselian for all reasonable adjustments to water content estimates and other parameters. The new ages suggest that climate was relatively mild and that the Scandinavian Ice Sheet was absent or restricted to the mountains for at least parts of MIS 3. These results are supported by other recent studies completed in Fennoscandia.

  • 27.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Landvik, Jon Y.
    Ryen, Heidi T.
    Chronology and styles of glaciation in an inter-fjord setting, northwestern Svalbard2011Ingår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 40, nr 1, s. 175-197Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 30-m-thick sedimentary succession at Leinstranda on the southwestern coast of Brøggerhalvøya, northwestern Svalbard, spans the two last glacial–interglacial cycles and reveals information on glacial dynamics, sea-level changes and the timing of these events. We investigated the deposits using standard stratigraphical and sedimentological techniques, together with ground-penetrating radar, and established an absolute chronology based mainly on optically stimulated luminescence dating. We identi?ed facies associations that represent depositional settings related to advancing, overriding and retreating glaciers, marine and littoral conditions and periglacial surfaces. The environmental changes show an approximate cyclicity and reflect glaciations followed by high sea levels and later regression. The luminescence chronology places sea-level highstands at 185±8 ka, 129±10 ka,99±8 ka and 36±3 ka. These ages constrain the timing of recorded glaciations at Leinstranda to prior to c. 190 ka, between c. 170 and c. 140 ka (Late Saalian) and between c. 120 ka and c. 110 ka (Early Weichselian). The glaciations include phases with glaciers from three different source areas. There is no positive evidence for either Middle or Late Weichselian glaciations covering the site, but there are hiatuses at those stratigraphic levels. A high bedrock ridge separates Leinstranda from the palaeo-ice stream in Kongsfjorden, and the deposits at Leinstranda reflect ice-dynamic conditions related to ice-sheet evolution in an inter-fjord area. The environmental information and theabsolute chronology derived from our data allow for an improved correlation with the marine record, and for inferences to be made about the interaction between land, ocean and ice during the last glacial–interglacial cycles.

  • 28.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Murray, Andrew
    Problems and potential of OSL-dating deglacial and interstadial sediments in Sweden2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Several recent OSL-ages from Sweden have been inconsistent with geological interpretation, commonly due to age overestimation, and have been met with some scepticism. We explore the problems and potential of OSL-dating in Sweden by analysing quartz OSL-ages from several known-age deglacial sites in southern and central Sweden and by investigating their luminescence properties. Two problems for obtaining good and reliable ages are incomplete bleaching and low-sensitivity quartz. Incomplete bleaching is partly, but not entirely, the cause of age overestimation and can be avoided by selecting suitable sediment facies. Low sensitivity leads to practical problems in measurements and larger uncertainties in dose estimates. On the other hand, potential for good OSL-dating is shown by high-sensitivity quartz from sites that contain both Dala sandstone clasts and sediments that may have had extensive reworking during the Quaternary.

    This knowledge is useful for interpreting OSL-results from unknown-age interstadial sites. Most interstadial sites in Sweden contain only fragmentary records and represent single events and OSL-ages from such sites lack a context to which the results can be related. It is for example rarely possible to get OSL-samples from a stratigraphic succession that spans a significantly longer time than the resolution of the method or find sites where dates from more than one stratigraphically overlying interglacial, interstadial or deglacial bed can be compared. As interstadial OSL-ages thus largely have to stand on their own, multiple samples and detailed data analyses are necessary to give credibility to the results given the Swedish record of OSL-difficulties. From a luminescence point of view, sites fulfilling the positive criteria identified for deglacial deposits should be selected, but the setting and nature of the most geologically interesting interstadial sites are not always obliging.

  • 29.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Murray, Andrew
    Småland, south Sweden – a bleak place for luminescence dating or an area that will change Scandinavian glacial history?2007Ingår i: 9th International Conference “Methods of absolute chronology”, 2007Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 30.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Murray, Andrew S
    Problems and potential of OSL dating Weichselian and Holocene sediments in Sweden2010Ingår i: Abstracts and Proceedings of the Geological Society of Norway, NGF Number 1, 2010, 2010, s. 3-4Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Recent OSL dating of various Late Quaternary deposits in Sweden has resulted in several sets of ages that appear inconsistent with geological interpretation; they usually overestimate the expected age. We explore the problems and potential of OSL dating in Sweden by analysing quartz OSL-ages from several known-age sites in Sweden and by investigating their luminescence properties. Two difficulties in obtaining accurate and precise ages are incomplete bleaching and low-sensitivity quartz. Incomplete bleaching can give rise to age overestimation, but the importance of this effect can be minimised by selecting suitable sediment facies, although for some settings unexplained overestimates still remain. Low quartz OSL sensitivity leads to practical problems in measurements and larger uncertainties in dose estimates, but not necessarily to systematic age overestimation. Sites that contain Dala sandstone clasts and/or sediments that may have had extensive reworking during the Quaternary seem to provide high-sensitivity quartz. We consider such sites to show the most potential for accurate and precise OSL-dating in Sweden.

    For typical Swedish material, the scatter in doses makes OSL-ages less precise and the method cannot usually compete with radiocarbon dating for young (Late Weichselian-Holocene) sediments unless the deposits simply lack organic material. The lowest overall uncertainty for the samples in this study is 4% of the age (average is 7%) and we expect that OSL ages from Sweden cannot be much better known than this. A 5-10% precision in age is, however, usually not a problem for older sediments and OSL can advantageously be used to date for example interstadial deposits. Nevertheless, given the Swedish record of OSL-difficulties it is important to work with multiple samples and adapt analytical protocols to each site or sample to give credibility to the results.

  • 31.
    Alexanderson, Helena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi.
    Murray, Andrew S.
    Was southern Sweden ice free at 19–25 ka, or were the post LGM glacifluvial sediments incompletely bleached?2007Ingår i: Quaternary Geochronology, ISSN 1871-1014, Vol. 2, nr 1-4, s. 229-236Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Glacifluvial deposits along an ice-marginal zone in Småland, southern Sweden, have been dated using post-IR blue OSL. To test for incomplete bleaching, we adopted two strategies: analysis of modern analogues and small-aliquot dose distributions. Samples of modern fluvial sediments show no significant incomplete bleaching; they yield equivalent doses of only 0.5-2 Gy (~0.25-4% of our glacifluvial sediment doses). Small-aliquot dose distributions do not provide any evidence for incomplete bleaching. The sediments are believed to have been deposited during deglaciation and appear to fall into two age groups: 19-25 ka (mainly sandur sediments) and 33-73 ka (mainly deltaic sediments). Compared to the expected ages (13-15 ka), even the younger glacifluvial OSL ages appear up to 10 000 years (~25 Gy) too old. The ages are nevertheless stratigraphically consistent and correspond between sites; we deduce that the 19-25 ka ages are true deposition ages. For glacifluvial sedimentation to take place on the South Swedish Upland at this time either a very early deglaciation is required, or alternatively ice-free conditions just prior to the LGM. The deltaic sediments (33-73 ka) were most likely not significantly bleached during deposition and thus they date events prior to the latest ice advance.

  • 32.
    Allard, Anna
    et al.
    Institutionen för Skoglig Resurshushållning .
    Skånes, Helle
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Miljöövervakning via infraröda flygbilder, ett väl använt verktyg med goda framtidsutsikter i Sverige2010Ingår i: Kart- och bildteknik (Mapping and Image Science), Vol. 4, s. 20-23Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 33.
    Ampel, Linda
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Dansgaard-Oeschger cycles and Heinrich events in western Europe - A diatom perspective2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The last glacial period was characterised by several abrupt climatic shifts referred to as Dansgaard-Oeschger (DO) cycles and Heinrich events. These shifts were most frequent between 60,000 and 20,000 years before present coinciding with Marine Isotope Stages (MIS) 3 and 2. DO cycles and Heinrich events have been most thoroughly investigated in marine and ice core records while their impact on terrestrial environments is less well known. The high-resolution, multi-proxy investigation of a long sediment sequence, obtained from the former lake at Les Echets in France, aims at filling this gap and allows determining the impact of these climatic events on the lake and its catchment. The site and its surroundings experienced distinct shifts in lake organic productivity and catchment conditions as a consequence of DO climate variability and Heinrich events. The detailed analysis of the fossil diatom record shows distinct changes in diatom productivity, diversity and community composition, which are most likely due to variations in the length of lake ice cover, thermal stratification regimes and catchment conditions during a DO cycle. The distinct reduction in lake organic productivity and particularly low concentrations of diatom valves during intervals corresponding to Heinrich events suggest that these cold and arid phases had the most severe impact on the paleolake at Les Echets. The results of this thesis provide new insight into the impact of abrupt climate change on lacustrine ecosystems and show the potential of high-resolution and multi-proxy studies in paleoenvironmental research.

  • 34.
    Ampel, Linda
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Bigler, Christian
    Department of Ecology and Environmental Science, Umeå University.
    Wohlfarth, Barbara
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Risberg, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Lotter, André F.
    Institute of Environmental Biology, Laboratory of Palaeobotany and Palynology, Utrecht University.
    Veres, Daniel
    “Emil Racovita” Speleological Institute, Clinicilor 5, 400006 Cluj-Napoca, Romania.
    Modest summer temperature variability during DO cycles in western Europe2010Ingår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 29, nr 11-12, s. 1322-1327Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abrupt climatic shifts between cold stadials and warm interstadials, termed Dansgaard-Oeschger (DO) cycles, occurred frequently during the Last Glacial. Their imprint is registered in paleorecords worldwide, but little is known about the actual temperature change both annually and seasonally in different regions. A recent hypothesis based on modelling studies, suggests that DO cycles were characterised by distinct changes in seasonality in the Northern Hemisphere. The largest temperature change between stadial and interstadial phases would have occurred during the winter and spring seasons, whereas the summer seasons would have experienced a rather muted temperature shift. Here we present a temporally high-resolved reconstruction of summer temperatures for eastern France during a sequence of DO cycles between 36 and 18 thousand years before present. The reconstruction is based on fossil diatom assemblages from the paleolake Les Echets and indicates summer temperature changes of ca 0.5–2 °C between stadials and interstadials. This study is the first to reconstruct temperatures with a sufficient time resolution to investigate DO climate variability in continental Europe. It is therefore also the first proxy record that can test and support the hypothesis that temperature changes during DO cycles were modest during the summer season.

  • 35.
    Ampel, Linda
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Bigler, Christian
    Wohlfarth, Barbara
    Risberg, Jan
    Lotter, André F.
    Veres, Daniel
    Modest summer temperature variability during DO cycles in western Europe - an answer to a long time paradox?Manuskript (Övrigt vetenskapligt)
  • 36.
    Ampel, Linda
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Wohlfarth, Barbara
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Risberg, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Veres, Daniel
    Paleolimnological response to millennial and centennial scale climate variability during MIS 3 and 2 as suggested by the diatom record in Les Echets, France2008Ingår i: Quaternary Science Reviews, ISSN 0277-3791, Vol. 27, nr 15-16, s. 1493-1504Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 27 m long sediment sequence retrieved from the central part of the Les Echets basin in France has been analysed in sub-centennial resolution for biogenic silica and fossil diatom remains. The sequence corresponds to the later part of Marine Isotope Stage (MIS) 3 and to most of MIS 2. Distinct changes in diatom productivity, diversity and taxonomic composition between 36.2 and 31.7 kyr BP appear to relate to Dansgaard–Oeschger (DO) climate variability. Intervals characterized by low diversity, productivity and small-sized benthic diatom taxa are most likely a response to colder conditions in relation to DO stadials. In contrast, higher diversity, productivity and a high abundance of planktonic taxa indicate a response to warmer temperatures during DO interstadials. The time interval between 30.3 and 15.7 kyr BP is characterized by continuous low diatom productivity and a benthic dominated community with intermediate species richness, suggesting a transition to more stable conditions. Three time intervals with extremely low concentrations of diatom valves (46.1–36.2, 31.7–30.3 and 26.3–23.6 kyr BP) overlap with ages reported for Heinrich (H) events 4, 3, and 2. We speculate that the lake at Les Echets suffered from severe ecological stress as a response to H events. This is the first detailed study exemplifying the response of a lake, based on diatoms, to climate variability during late part of MIS 3 and most of MIS 2 in Europe.

  • 37.
    Ampel, Linda
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Wohlfarth, Barbara
    Risberg, Jan
    Veres, Daniel
    Leng, Melanie J.
    Kaislahti Tillman, Päivi
    Diatom community dynamics during abrupt climate change: the response of lacustrine diatoms to Dansgaard-Oeschger cycles during the last glacial periodManuskript (Övrigt vetenskapligt)
  • 38.
    Ampel, Linda
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Wohlfarth, Barbara
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Risberg, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Veres, Daniel
    Leng, Melanie
    Kaislahti Tillman, Päivi
    Diatom assemblage dynamics during abrupt climate change: The response oflacustrine diatoms to Dansgaard-Oeschger cycles during the last glacialperiod2010Ingår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 44, nr 2, s. 397-404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The sedimentary record from the paleolake at Les Echets in eastern France allowed a reconstruction of the lacustrine response to several abrupt climate shifts during the last glacial period referred to as Dansgaard-Oeschger (DO) cycles. The high-resolution diatom stratigraphy has revealed distinct species turnover events and large fluctuations in stable oxygen isotope values in diatom frustules, as a response to DO climate variability. More or less identical species compositions became re-established during each DO stadial and interstadial phases, respectively. However, the relative abundance of the most dominant species within these assemblages varies and might indicate differences in climatic conditions. Interstadial phases are characterized by identical species successions. Transitions from stadial to interstadial conditions show a distinct Fragilaria-Cyclotella succession, which resembles the diatom regime shifts that have been recognized in some lakes in the Northern Hemisphere since the mid-nineteenth century.

  • 39.
    Andersson, Emma
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Jämställd samhällsplanering - en möjlighet för Stockholm?: En studie om framväxten av Hjorthagen, Norra Djurgårdsstaden2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Många byggprojekt håller på att genomföras i Stockholm för att möta befolkningsökningen. Uppsatsens syfte är att ta reda på och redovisa om och hur de involverade aktörerna i byggnationen av Hjorthagen, Norra Djurgårdsstaden i Stockholm arbetar med genus- och jämställdhetsfrågor. Frågan är om Hjorthagen kommer att kunna bli en mer jämställd stadsdel än de övriga i Stockholm. Hypotesen som uppsatsen fokuserat kring är att ambitionerna att skapa en ökad jämställhet finns men att de inte införlivas.

    Den svenska staten försöker implementera jämställdhetsarbetet inom de flesta områden idag men samhällsplaneringen har inte visat något större intresse för detta. Det är Stockholms stad som har det övergripande ansvaret för den fysiska planeringen i Stockholm men också för den sociala hållbarheten där jämställdhet räknas in. Det finns flertalet dokument från bland annat Trafikverket (tidigare Vägverket), Stockholms stad och andra aktörer om hur jämställdhetsproblem ska tacklas men ännu syns inga tecken på sådan aktivitet i den fysiska planeringen. Samhällsplaneringen har i princip alltid varit könsblind och är fortfarande idag, så även i Sverige. Inom samhällsplaneringen betyder detta att kvinnors behov och erfarenheter inte uppmärksammas och man fortsätter att befästa och reproducera denna ojämställdhet.

    Studien som har genomförts är av kvalitativ typ och har analyserat intervjumaterial, litteratur och dokument för tydliggöra hur genus- och jämställdhetsfrågor behandlas av de inblandade aktörerna. Det är en deduktiv och hermeneutisk studie som till största del baseras på intervjuer av semistrukturerad natur. Intervjuerna har skett öga mot öga med representanter från Stockholms stad, politiker, byggföretag med flera.

    Resultatet av studien visar att jämställdhetsfrågan inte berörs i någon större utsträckning inom fysisk planering. En långsiktig framtidsvision publicerades 2007 där det fanns en önskan om att göra Stockholm till världens mest jämställda huvudstad till år 2030. Detta är dock något som inte syns idag. Det empiriska materialet visar på att Hjorthagen troligtvis inte kommer att bli en mer jämställd stadsdel än de övriga i Stockholm eftersom inget arbete för detta sker.

  • 40.
    Andersson, Emmelie
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Vulkanisk svaveldimma: Risken att det drabbar Sverige2011Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the year 1783 a fissure eruption from Laki in the southern part of Iceland produced a large amount of volcanic gases during a period of eight months. The volcanic gases and aerosols spread across the northern hem sphere due to ideal weather conditions and had a substantial impact on the environment, human health and also climate effects. This, so called dry fog, caused severe health problems, which led to death casualties, killing animals, crops and other vegetation. The consequence was a widespread famine which was aggravated by a hard and long winter in 1783/84. Analysis shows that the Icelandic volcanoes are the primary risk to produce dry fog that can affect Sweden. The fog will most likely cause severe health effects, such as respiratory and cardiovascular problems. It will also cause damage to the vegetation, especially coniferous trees, and it may affect the water by acid chock. The fog may have great impact on the critical infrastructure in Sweden, depending on magnitude and duration. These types of volcanic hazards are difficult to predict and evaluate due to their sporadic nature and the sparse amount of data that is available. It is therefore important to focus on the consequences and develop the Swedish community preparedness on a general basis to handle this type of event.

  • 41.
    Andersson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre.
    Lindborg, Regina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Species Richness and Assemblages in Landscapes of Different Farming Intensity - Time to Revise Conservation Strategies?2014Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 10, s. e109816-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Worldwide conservation goals to protect biodiversity emphasize the need to rethink which objectives are most suitable for different landscapes. Comparing two different Swedish farming landscapes, we used survey data on birds and vascular plants to test whether landscapes with large, intensively managed farms had lower richness and diversity of the two taxa than landscapes with less intensively managed small farms, and if they differed in species composition. Landscapes with large intensively managed farms did not have lower richness than smaller low intensively managed farms. The landscape types were also similar in that they had few red listed species, normally targeted in conservation. Differences in species composition demonstrate that by having both types of agricultural landscapes regional diversity is increased, which is seldom captured in the objectives for agro-environmental policies. Thus we argue that focus on species richness or red listed species would miss the actual diversity found in the two landscape types. Biodiversity conservation, especially in production landscapes, would therefore benefit from a hierarchy of local to regional objectives with explicit targets in terms of which aspects of biodiversity to focus on.

  • 42.
    Andersson, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre.
    Nykvist, Björn
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre. Stockholms universitet, Stockholm Environment Institute.
    Malinga, Rebecka
    Stockholms universitet, Naturvetenskapliga fakulteten, Stockholm Resilience Centre.
    Jaramillo, Fernando
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Lindborg, Regina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    A social-ecological analysis of ecosystem services in two different farming systems2015Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, s. 102-112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this exploratory study we use existing in situ qualitative and quantitative data on biophysical and social indicators to compare two contrasting Swedish farming systems (low intensity and high intensity) with regard to ecosystem service supply and demand of a broad suite of services. We show that the value (demand) placed on a service is not necessarily connected to the quantity (supply) of the service, most clearly shown for the services recreation, biodiversity, esthetic experience, identity, and cultural heritage. To better capture this complexity we argue for the need to develop portfolios of indicators for different ecosystem services and to further investigate the different aspects of supply and demand. The study indicates that available data are often ill-suited to answer questions about local delivery of services. If ecosystem services are to be included in policy, planning, and management, census data need to be formatted and scaled appropriately.

  • 43.
    Andersson, Ingela
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Implementing the European Water Framework Directive at local to regional level -Case Study Northern Baltic Sea River Basin District, Sweden2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 44.
    Andersson, Ingela
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Petersson, Mona
    Saving the Baltic Sea, the Inland Waters of Its Drainage Basin, or Both?: Spatial Perspectives on Reducing P-Loads in Eastern Sweden2014Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 43, nr 7, s. 914-925Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nutrient loads from inland sources to the Baltic Sea and adjacent inland waters need to be reduced in order to prevent eutrophication and meet requirements of the European Water Framework Directive (WFD) and the Baltic Sea Action Plan (BSAP). We here investigate the spatial implications of using different possible criteria for reducing water-borne phosphorous (P) loads in the Northern Baltic Sea River Basin District (NBS-RBD) in Sweden. Results show that most catchments that have a high degree of internal eutrophication do not express high export of P from their outlets. Furthermore, due to lake retention, lake catchments with high P-loads per agricultural area (which is potentially of concern for the WFD) did not considerably contribute to the P-loading of the Baltic Sea. Spatially uniform water quality goals may, therefore, not be effective in NBS-RBD, emphasizing more generally the need for regional adaptation of WFD and BSAP-related goals.

  • 45.
    Andersson, Ingela
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Petersson, Mona
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Impact of the European Water Framework Directive on local-level water management: Case study Oxunda Catchment, Sweden2012Ingår i: Land use policy, ISSN 0264-8377, E-ISSN 1873-5754, Vol. 29, nr 1, s. 73-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Water Framework Directive (WFD) of the European Union provides a common framework for waterpolicy that focuses on holistic and integrated water management in river basins. In many member states,implementation of the WFD has shifted the main responsibility for local water issues from the municipallevel to the regional or supra-regional levels. In this study, we investigated how the implementation of theWFD has influenced local-level water management including the interpretation of the new environmentalquality standards. Specifically, we considered Sweden, which has traditionally had relatively stronggovernance at the municipal level. Because a sufficient amount of time has now passed for evaluationof WFD-related effects on operational water handling, we interviewed individuals directly involved inwater planning and land use planning at the municipal level in one sub catchment in the Northern BalticSea River Basin District of Sweden, as well as representatives for superior levels and associations. Despitedivergent views regarding the priority of water issues in physical planning among the local-level plannersinterviewed, they had all participated in successful inter-municipal pre-WFD collaboration projects.Although such collaborations could help increase the understanding and acceptance of WFD-related goalsand costs, as well as facilitate conflict solving, as shown in the Oxunda Catchment, they have not gainedmuch attention in the WFD implementation process. Additionally, physical planners have generally beenreluctant to accept new environmental quality standards resulting from WFD implementation, in partbecause they lack precise definitions, but also because they could challenge the municipal routine ofweighing various objectives against each other. Furthermore, despite WFD-related increases in ambitionlevels, lack of resource improvements at the municipal level were identified as potential problems by local environmental planners.

  • 46.
    Andersson, Kajsa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    How important are small remnant habitats for biodiversity in the agricultural landscape?2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The consequences of the agricultural intensification are many and include fragmentation of natural habitats, abandonment of small farms and traditional management, and increased inputs of pesticides and fertilizers. It has also lead to widespread declines in semi-natural grasslands and farmland biodiversity. Small remnant habitats such as midfield islets and road verges can harbour many species and hence be important in biodiversity conservation. This study investigated how plant species richness and richness of grassland specialists differ in three agricultural landscapes: one open landscape with crop fields, one with a lot of forest and one landscape with a mix of forests and fields. Field studies included plant inventories in the small remnant habitats. Species-area relationships, accumulated species curves and Jaccard similarity index were used to analyze the data, where total species richness and grassland specialists were analysed separately. It was found that the two landscapes with the most forest had higher species richness in midfield islets, but not in road verges, and that the intermediate landscape had the strongest species-area relationship. Species accumulation curves show the fastest species accumulation rate for midfield islets in the forest landscape and for road verges in the open landscape. The remnant habitats in the forest and intermediate landscapes were most similar to the semi-natural grassland in that landscape. The connectivity of the landscape, as well as the presence of semi-natural grasslands may help to explain the results. This study shows that small remnant habitats could be important for biodiversity conservation in agricultural landscapes and that managing the landscape in a way that preserves heterogeneity may be crucial for its continued species richness.

  • 47.
    Andersson, Linus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Samförvaltning av Tyresta nationalpark och naturreservat?: En undersökning av förvaltningsmodellenoch lokalt deltagande2010Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Lokalt inflytande och delaktighet i naturresursförvaltning och naturvård är något som fått alltmer uppmärksamhet under de senaste decennierna, vilket speglas i internationella konventioner och i initiativ för lokal delaktighet i naturvården. Utvecklingen av lokalt förankrade förvaltningsformer i skyddade områden kan ses som en del av en reaktion mot en expertorienterad naturvård som kännetecknats av centralstyrning och strikt bevarande av ”ursprunglig” natur. Samförvaltning är ett exempel på en mer deltagarorienterad styrform som innebär olika typer av partnerskap mellan statliga, regionala och lokala aktörer. Hur sådana lokala förvaltningsformer fungerar i praktiken är dock omdiskuterat. Deltagandet i t.ex.nationalparker anses av flera forskare vara fortsatt begränsat och kan syfta till att öka acceptansen för myndigheters bevarandelinje. Uppsatsen behandlar frågan om lokal delaktighet iskyddade områden genom en fallstudie av Tyresta nationalpark och naturreservat ur ett samförvaltningsperspektiv. Detta område förvaltas sedan 1993 av Stiftelsen Tyrestaskogen, som inkluderar representanter från Naturvårdsverket, Länsstyrelsen i Stockholms län, Stockholms stad, Tyresö kommun och Haninge kommun. Syftet är att analysera lokalt deltagande vad gäller skötsel och förvaltning av Tyresta nationalpark och naturreservat, och på vilka sätt lokalt deltagande i området, avseende både kommuner och andra lokala aktörer, kan kopplas till stiftelseformen som förvaltningsmodell. Kvalitativa intervuer har gjorts med representanter för naturvårdsverket, de berörda kommunerna, och för olika intressentgrupper i området, för att få en bild av förvaltningssituationen samt av intressen och uppfattningar om lokalt deltagande vad gäller förvaltning och skötsel. Resultaten visar att förvaltningsmodellen innebär ett lokalt deltagande på kommunalnivå i form av ett partnerskapsarrangemang, men att den har mindre betydelse för lokala aktörsgrupper, vilka inte är involverade i ett formellt beslutsfattande. Förvaltningsmodellen ses av kommunrepresentanterna som något som förhindrat större konfliker. Förtroende från från lokala aktörsgruppers sida gentemot förvaltaren kan också kopplas till ett lokalt deltagande, dock inte som en direkt följd av stiftelseförvaltningen. De få konflikterna och det relativt begränsade engagemanget kan dock också förstås utifrån det begränsade resursberoendet och en gemensam syn på landskapets och naturens värden. Det finns dock lokala synpunkter och mindre konflikter, vilka tillsammans med det lokala deltagandets karaktär indikerar ett rådande bevarandeperspektiv i linje med en traditionell naturvårdssyn.

  • 48.
    Andersson, Marcus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Estimating Phosphorus in rivers of Central Sweden using Landsat TM data2012Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Phosphorus flowing via rivers into the Baltic Sea is a major source of nutrients, and in some cases the limiting factor for the growth of algae which causes the phenomenon known as eutrophication. Remote sensing of phosphorus, here using Landsat TM-data, can help to give a better understanding of the process of eutrophication. Since Landsat TM-data is used, this could form a basis for further spatio-temporal analysis in the Baltic Sea region. A method originally described and previously applied for a Chinese river is here transferred and applied to three different rivers flowing into the Baltic Sea. The results show that by measuring the proxy variables of Secchi Depth and Chloryphyll-a the remote sensing model is able to explain 41% of the variance in total- phosphorus for the rivers Dalälven, Norrström and Gavleån without any consideration taken to CDOM, turbidity or other local features.

  • 49.
    Andersson, Rina Argelia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Meyers, Philip
    Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, Michigan, U.S.A..
    Zebür, Yngve
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mörth, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic2011Ingår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 42, nr 9, s. 1065-1075Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coupled analyses of n-alkane biomarkers and plant macrofossils from a peat plateau deposit in the northeast European Russian Arctic were carried out to assess the effects of past hydrology on the molecular contributions of plants to the peat. The n-alkane biomarkers accumulated over 9.6 kyr of local paleohydrological changes in this complex peat profile in which a succession of vegetation changes occurred during a transition from a wet fen to a relatively dry peat plateau bog. This study shows that the contribution of the n-C31 alkane from rootlets to peat layers rich in fine and dark roots is important. The results further indicate that the n-alkanePaqandn-C23/n-C29 biomarker proxies that have been useful to reconstruct past water table levels in many peat deposits can be misleading when the contributions of Betulaand Sphagnum fuscum to the peat are large. Under these conditions, the C23/(C27+ C31) n-alkane ratio seems to correct for the presence of BetulaandS. fuscum and provides a better description for the relative amounts of moisture. The average chain length (ACL) n-alkane proxy also appears to be a good paleohydrology proxy in having larger values during dry and cold conditions in this Arctic bog setting.

  • 50.
    Andersson, Rina Argelia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Meyers, Philip
    Hornibrook, Edward
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Morth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic2012Ingår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 27, nr 6, s. 545-552Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (similar to 2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss-dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. delta 15N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in delta 13C values appear to reflect mainly changes in plant assemblages. Positive shifts in both delta 15N and delta 13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N-enrichment.

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