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  • 301.
    Gribenski, Natacha
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Preusser, Frank
    Harbor, Jonathan M.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Trauerstien, Mareike
    Blomdin, Robin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Heyman, Jakob
    Caffee, Marc W.
    Lifton, Nathaniel
    Zhang, Wei
    Major glaciation in Central Asia during MIS 3: reality or dating artefact?Manuscript (preprint) (Other academic)
    Abstract [en]

    Previous investigations have concluded that a period of major glacial advances occurred during Marine Isotope Stage (MIS) 3 (57-29 ka) in Central Asia, out of phase with global ice volume records. We have re-examined the Kanas moraine complex in the Altai Mountains, where an MIS 3 glaciation has been previously inferred. New cosmogenic exposure and single grain luminescence ages indicate that the Kanas complex was formed during MIS 2 (29-12 ka); we regard the initial MIS 3 interpretation as a result of dating artefacts. Building on this example, we reanalyze chronological data associated with proposed major MIS 3 glacial advances in Central Asia (24 sites). We find that chronological data do not allow glaciation timing inferences for most of the sites, and that chronological evidence for major MIS 3 glacial advance only exists at one site.

  • 302.
    Gribenski, Natacha
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lukas, Sven
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Krister N.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Harbor, Jonathan M.
    Stockholm University, Faculty of Science, Department of Physical Geography. Purdue University, USA.
    Blomdin, Robin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ivanov, Mikhail N.
    Heyman, Jakob
    Petrakov, Dmitry A.
    Rudoy, Alexei
    Clifton, Tom
    Lifton, Nathaniel A.
    Caffee, Marc W.
    Reply to comment received from J. Herget et al. regarding "Complex patterns of glacier advances during the late glacial in the Chagan Uzun Valley, Russian Altai" by Gribenski et al. (2016), Quaternary Science Reviews 149, 288-3052017In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 168, p. 219-221Article in journal (Other academic)
  • 303.
    Gribenski, Natacha
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Preusser, Frank
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Greilich, Steffen
    Huot, Sebastien
    Mittestrass, Dirk
    Investigation of cross talk in single grain luminescence measurements using an EMCCD camera2015In: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 81, p. 163-170Article in journal (Refereed)
    Abstract [en]

    Highly sensitive electron multiplying charges coupled devices (EMCCD) enable the spatial detection of luminescence emissions from samples and have a high potential in single grain luminescence dating. However, the main challenge of this approach is the potential effect of cross talk, i.e. the influence of signal emitted by neighbouring grains, which will bias the information recorded from individual grains. Here, we present the first investigations into this phenomenon when performing single grain luminescence measurements of quartz grains spread over the flat surface of a sample carrier. Dose recovery tests using mixed populations show an important effect of cross talk, even when some distance is kept between grains. This issue is further investigated by focusing just on two grains and complemented by simulated experiments. Creation of an additional rejection criteria based on the brightness properties of the grains is inefficient in selecting grains unaffected by their surroundings. Therefore, the use of physical approaches or image processing algorithms to directly counteract cross talk is essential to allow routine single grain luminescence dating using EMCCD cameras.

  • 304.
    Groth, Erika
    Stockholm University, Faculty of Science, Department of Physical Geography.
    En studie av sambandet mellan urbanisering och maximiflödena i Hagbyån i Stockholms län2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The population in the Stockholm region has increased in the last few decades and this population increase is expected to continue in the future. Increased urbanization normally means that the fraction of impervious surfaces increases. On impervious surfaces such as roofs, roads and parking lots water cannot infiltrate the ground but run off as surface runoff. An increased fraction of impervious surfaces is therefore assumed to result in higher and faster runoff, especially at heavy rainfall, which increases the risk of flooding. In Stockholm county the ongoing climate change is expected to result in increased precipitation, especially in winter, and extreme precipitation events are also expected to become more common.

    In this study I investigate the connection between the degree of urbanization, measured both as population density and as the fraction of impervious surfaces, and the size of the yearly peak flows in Hagbyån near Vallentuna from the second half of the 20th century until today. Impervious surfaces are defined in this study as buildings, roads, rail roads and paths and calculated based on the property map (fastighetskartan) which represents the present day and the economical map (ekonomiska kartan) which represents the beginning of the study period. The recurrence interval of the annual peak flows was calculated from the daily flow values at Skällnora hydrological station using frequency analysis according to the three methods the Weibull method, the Gringorten method and the Gumbel method.

    The study area has, as expected, become more urbanized during the study period. Both the population in the municipalities and the population in the largest town in the study area have increased and the fraction of impervious surfaces has nearly doubled from the beginning of the study period until today. Despite this the size of the annual peak flows has diminished. When the size of the 100-year flow at the Skällnora station is calculated based on the yearly peak flows of first half of the study period the 100-year flow is 3,9 m3/s but when the yearly peak flows from the second half of the study period are used the 100-year flow is 2,4 m3/s. The largest annual peak flows have become more rare. This contradicts the expected result which was that the annual peak flows would increase when the fraction of impervious surfaces increased.

    This result is not due to reduced precipitation. This study did not include an analysis of changes in evapotranspiration over time in the area. A warmer climate with less snow and a shift of the precipitation pattern to more precipitation in winter might be part of the explanation.

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  • 305.
    Groß, Elisabeth
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mård, Johanna
    Kalantari, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Links between Nordic and Arctic hydroclimate and vegetation changes: Contribution to possible landscape-scale nature-based solutions2018In: Land Degradation and Development, ISSN 1085-3278, E-ISSN 1099-145X, Vol. 29, no 10, p. 3663-3673Article in journal (Refereed)
    Abstract [en]

    In Nordic and Arctic regions, the rapidly warming climate sustains hydroclimatic and vegetation changes in the landscape. There is evidence for an increase in vegetation density in some regions, a trend that is expected as a response to increasing temperature and precipitation. If the hydroclimatic changes are linked to vegetation response, it could be viewed as a landscape-scale nature-based solution (NBS) that could moderate the runoff response, as denser vegetation should lead to increased evapotranspiration and lower runoff. In this paper, we investigate and compare hydroclimatic changes over a set of basins in the Nordic region and northwest America and compare with changes in vegetation density, analyzed using the normalized difference vegetation index (NDVI) for three time periods: 1973-1978, 1993-1998, and 2013-2016. Over the period of the 1970s to 1990s, the hydroclimate became warmer and wetter and vegetation density increased, but over a later period from the 1990s to 2010s, vegetation density decreased, despite a continuing warming and wetting of the climate. Although there was a tendency for runoff to decrease in basins where vegetation density increased, the relation between precipitation and runoff was much stronger. Overall, we found weak evidence for vegetation density changes, driven by hydroclimate, to act as NBS on the landscape scale over the studied regions. However, as hydroclimatic changes interact with vegetation changes and their ensuing hydrological responses in complex ways, more detailed investigations are needed to determine the potential NBS effect on the landscape scale across Nordic and Arctic regions.

  • 306.
    Guittard, Alice
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Identifying active water flow paths in a tropical wetland with radar remote sensing data (wetland interferometry): The case of the Cienaga Grande de Santa Marta, Colombia2016Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Despite being one of the most productive ecosystems on earth, wetland areas have been heavily affected by human activities. The Cienaga Grande de Santa Marta (CGSM) in Colombia is one of these wetlands, where the inadequate construction of roads modified the hydrology and connectivity of this water body, generating massive mangrove mortality episodes. The lack of knowledge on the hydrological processes and connectivity of the CGSM has impaired mangrove restoration plans. Here we use wetland interferometry technique to remotely monitor the wetland and understand the flow of water in/out and across the CGSM wetland complex. A close collaboration with Miami University allowed us to access CGSM’s interferograms created with ALOS Palsar satellite data (from 2007 until 2011). The interferograms resulting from the analysis were correlated with daily hydrological data (precipitation, runoff in the main inflow of freshwater to the wetland, tide charts) to finally identify two main paths of inflow of water that are still active and are continuously feeding freshwater into the Cienaga. The most persistent was identified in the south-west part of the CGSM; a water flow coming directly from the Magdalena River and entering the main lagoon in its south-west corner. The second was located in the north-west area, where most of the mangroves have died. In this case, different interferograms showed different potential water flow paths depending on the season (dry / wet season), the Magdalena River’s discharge and the rainfall. These results reflect the complex hydrology of the CGSM . Furthermore, a coherence analysis was conducted to assess the quality of the remote sensing data and to better understand the different responses of the features within the Cienaga. The results showed that the coherence analysis could also be potentially used to identify areas of dead mangrove. This study confirms that despite the blockage of the connectivity of the wetlands, there are still important freshwater flow paths feeding the CGSM. Additional hydrological studies are needed to ensure the further understanding of the hydrology of the CGSM and confirm the results of this study.

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  • 307.
    Gullberg, Rebecka
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Carbon - Past, Present and Future: Effects of 20th century land use on soil organic carbon in Nynäs nature reserve, Sweden2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The land use sector has the potential not only to lower its greenhouse gas emissions, but also to sequester CO2 in soils through land use change and management practices. This represents an important mitigation opportunity, but there is a lack of knowledge in the potential of carbon sequestration between different land use types. This study examines soil organic carbon content and soil organic matter in a nature reserve in eastern middle Sweden. Methods include a change analysis of land use, values for soil organic carbon content from a literature review and soil samples for concentrations of soil organic matter. The study area has in terms of soil carbon been a source of atmospheric CO2 between 1945 and 1997, mainly due to a change from semi-natural grasslands to coniferous forest, resulting in a loss of 2209 tonnes of soil organic carbon. Results also show that wet grasslands and deciduous forests are the land use types with the highest potential to sequester carbon in shorter time spans. Older coniferous forests can store large amount of soil organic carbon, but younger coniferous forests and plantations, and cultivated lands were the land use types with the lowest values of soil organic carbon. Semi-natural grasslands have potential to store soil organic carbon but rates varied between samples and literature.

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  • 308. Gustafsson, Jon Petter
    et al.
    Belyazid, Salim
    Stockholm University, Faculty of Science, Department of Physical Geography.
    McGivney, Eric
    Löfgren, Stefan
    Aluminium and base cation chemistry in dynamic acidification models - need for a reappraisal?2018In: soil, ISSN 2199-3971, Vol. 4, no 4, p. 237-250Article in journal (Refereed)
    Abstract [en]

    Long-term simulations of the water composition in acid forest soils require that accurate descriptions of aluminium and base cation chemistry are used. Both weathering rates and soil nutrient availability depend on the concentrations of Al3+, of H+, and of base cations (Ca2+, Mg2+, Na+, and K+). Assessments of the acidification status and base cation availability will depend on the model being used. Here we review in what ways different dynamic soil chemistry models describe the processes governing aluminium and base cation concentrations in the soil water. Furthermore, scenario simulations with the HD-MINTEQ model are used to illustrate the difference between model approaches. The results show that all investigated models provide the same type of response to changes in input water chemistry. Still, for base cations we show that the differences in the magnitude of the response may be considerable depending on whether a cation-exchange equation (Gaines-Thomas, Gapon) or an organic complexation model is used. The former approach, which is used in many currently used models (e.g. MAGIC, ForSAFE), causes stronger pH buffering over a relatively narrow pH range, as compared to state-of-the-art models relying on more advanced descriptions in which organic complexation is important (CHUM, HD-MIN PLQ). As for aluminium, a fixed gibbsite constant, as used in MAGIC, SMART/VSD, and ForSAFE, leads to slightly more pH buffering than in the more advanced models that consider both organic complexation and Al(OH)(3) (s) precipitation, but in this case the effect is small. We conclude that the descriptions of acid-base chemistry and base cation binding in models such as MAGIC, SMART/VSD, and ForSAFE are only likely to work satisfactorily in a narrow pH range. If the pH varies greatly over time, the use of modern organic complexation models is preferred over cation-exchange equations.

  • 309.
    Gustav, Alm
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Vegetationsutvecklingen och människans påverkan på vegetationen kring Sojdmyr på Östra Gotland från cal 4000 BP till nutid2018Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Sojdmyr is a small wetland located 3 km east of Lina mire in eastern Gotland, Sweden, in an area highly affected by shoreline displacement. Archaeologists believe Lina mire was once part of a major inland water system used for commerce, and signs from several cultures around the Baltic Sea have been found in the area. This study aims to investigate the vegetational changes in the Sojdmyr area from about 4000 cal BP to the present, as well as discussing the human impacts that have contributed to these changes. Methods used have been pollen analysis, charcoal fragment counting and interpretation of the stratigraphy. The core was dated by correlation the results with other studies from Gotland. From the start of the Bronze Age, ca 4000–3000 cal BP, Sojdmyr was a freshwater lake. The vegetation in the landscape was open, with high presence of thermophilous taxa such as oak and elm and indications of pastoral land use. From the late Bronze Age to the Roman Iron Age (ca 3000–2000 cal BP) the mire Sojdmyr was characterized by fen peat. The thermophilous taxadropped quickly in abundance, whilst taxa more tolerate to cold conditions increased and the area became less open. From the Roman Iron Age (2000–1550 cal BP) to the present, Sojdmyr has changed intermittently between shallow freshwater lake and wetland conditions. According to the pollen analysis the first sign of cultivation in the area appeared with the introduction of rye during the Roman Iron Age, soon followed by barley at approximately ca 1500 cal BP. From the Iron Age to modern times the vegetation in the area became more open with signs of both agriculture and pastoral lands. The pollen record from Sojdmyr suggests that the land use in the area has been affected by shifts in climate during the Migration and Vendel Periods and the Little Ice Age.

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  • 310. Gut, Urs
    et al.
    Árvai, Mátyás
    Bijak, Szymon
    Julio Camarero, J.
    Cedro, Anna
    Cruz-García, Roberto
    Garamszegi, Balázs
    Hacket-Pain, Andrew
    Hevia, Andrea
    Huang, Weiwei
    Isaac-Renton, Miriam
    Kaczka, Ryszard J.
    Kazimirović, Marko
    Kędziora, Wojciech
    Kern, Zoltán
    Klisz, Marcin
    Kolář, Tomáš
    Körner, Michael
    Kuznetsova, Veronica
    Montwé, David
    Petritan, Any Mary
    Petritan, Ion Catalin
    Plavcová, Lenka
    Rehschuh, Romy
    Rocha, Eva
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rybníček, Michal
    Sánchez-Salguero, Raúl
    Schröder, Jens
    Schwab, Niels
    Stajić, Branko
    Tomusiak, Robert
    Wilmking, Martin
    Sass-Klaassen, Ute
    Buras, Allan
    No systematic effects of sampling direction on climate-growth relationships in a large-scale, multi-species tree-ring data set2019In: Dendrochronologia, ISSN 1125-7865, E-ISSN 1612-0051, Vol. 57, article id 125624Article in journal (Refereed)
    Abstract [en]

    Ring-width series are important for diverse fields of research such as the study of past climate, forest ecology, forest genetics, and the determination of origin (dendro-provenancing) or dating of archaeological objects. Recent research suggests diverging climate-growth relationships in tree-rings due to the cardinal direction of extracting the tree cores (i.e. direction-specific effect). This presents an understudied source of bias that potentially affects many data sets in tree-ring research. In this study, we investigated possible direction-specific growth variability based on an international (10 countries), multi-species (8 species) tree-ring width network encompassing 22 sites. To estimate the effect of direction-specific growth variability on climate-growth relationships, we applied a combination of three methods: An analysis of signal strength differences, a Principal Component Gradient Analysis and a test on the direction-specific differences in correlations between indexed ring-widths series and climate variables. We found no evidence for systematic direction-specific effects on tree radial growth variability in high-pass filtered ring-width series. In addition, direction-specific growth showed only marginal effects on climate-growth correlations. These findings therefore indicate that there is no consistent bias caused by coring direction in data sets used for diverse dendrochronological applications on relatively mesic sites within forests in flat terrain, as were studied here. However, in extremely dry, warm or cold environments, or on steep slopes, and for different life-forms such as shrubs, further research is advisable.

  • 311.
    Gärdsberg, Adam
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Geografiundervisning på högstadiet: Geografilärare med olika ämneskombinationer och deras syn på ämnet samt utformning av undervisning2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Gärdsberg, A. 2017. Geografiundervisning på högstadiet – Geografilärare med olika ämneskombinationer och dess ämnessyn samt utformning av undervisning. Naturgeografiska institutionen, Uppsatser, Stockholms Universitet. Den här studien undersöker hur geografilärare med olika ämneskombinationer på högstadiet ser på geografiämnet och hur de utformar sin undervisning och därigenom ta reda på ifall det är några skillnader mellan geografilärare som har en samhällsvetenskaplig ämneskombination och geografilärare med naturvetenskaplig ämneskombination. För att uppfylla syftet och besvara på frågeställningarna har kvalitativa intervjuer genomförts med aktuella lärare från båda lärargrupper. Det visar sig att bilden av geografiämnet är relativt likartad mellan grupperna och överensstämmer även med inflytelserika geografididaktikers beskrivning av ämnet. Lärarna i båda grupper lyfter fram ämnets tvärvetenskaplighet som en styrka vilket bidrar till en helhetssyn. Däremot finns det generella skillnader i hur grupperna utformar sin undervisning. Den samhällsvetenskapliga gruppens geografiundervisning domineras av kulturgeografiskt innehåll medan den naturvetenskapliga gruppen har en jämn fördelning av kultur- och naturgeografiskt innehåll samt värderar integreringen av båda discipliner högre. Keywords: Geografi, högstadiet, ämnessyn, didaktik, SO, NO Handledare: Cecilia Lundholm, HSD

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  • 312. Haase, Martina
    et al.
    Rösch, Christine
    Ketzer, Daniel
    Stockholm University, Faculty of Science, Department of Physical Geography. Karlsruhe Institute of Technology (KIT), Germany.
    GIS-based assessment of sustainable crop residue potentials in European regions2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 86, p. 156-171Article in journal (Refereed)
    Abstract [en]

    In this paper a novel model based on a geographic information system (GIS) is presented for the assessment of sustainable crop residue potentials. The approach is applied to analyse the amount and the spatial distribution (1 km × 1 km grid cells) of cereal straw, root crop and oil plant residues for five European regions, considering spatially differentiated environmental sustainability issues, i.e. organic carbon content in topsoil, soil erodibility, and protected areas. The maximum sustainable residue potential varies strongly between the regions and residue types. In the scenarios Basis and Restrict, it accounts for 45–59% and 24–48% of the theoretical potential respectively without considering competing uses. Among the crop residues, cereal straw shows the highest energy potential in all regions under investigation. In terms of wet mass it accounts for 3.7 Mio. twet/a in North Rhine-Westphalia, 1.6 Mio. twet/a in Île-the-France, 1.2 Mio. twet/a in Wallonia, 0.9 Mio. twet/a in West Midlands, and 0.3 Mio. twet/a in South Netherlands (scenario Basis). Our survey shows that spatially differentiated potential estimations and the inclusion of crop residues other than cereal straw are urgently needed to improve the present rough estimations for crop residues which can be used in a sustainable way. The rather high spatial resolution of our analyses particularly allows for the support of regional stakeholders and prospective investors when it comes to questions of regional availability of biomass resources, transport distances to biomass conversion plants, and identification of suitable plant sites and sizes, respectively.

  • 313.
    Haddad, Ola
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The effects of burn severity on soil properties: Infiltration rate, moisture, grain size distribution and carbon content Hälleskogsbrännan as an example2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study focuses on soil hydrological parameters that are expected to be related to burn severity in forests; infiltration rate, soil moisture, grain size distribution and carbon content along a burn severity gradient in Västmanland Sweden, where a major fire occurred in 2014. Hälleskogsbrännan was divided into two burn severities: a moderate severity and a high severity, and a control area. Ten soil samples were taken for laboratory analyses at each severity level. Soil moisture and infiltration rate was measured in situ. Infiltration rates and soil moisture were highest in the most severely affected site, whereas fire effects on soil texture were insignificant. Soil organic carbon content was highest at the low fire severity site, followed by control and high severity fire sites. Inorganic carbon content followed the opposite trend. These results had clear trends but were insignificant, this call for more comprehensive sampling to separate possible confounding site effects.

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  • 314.
    Haeffner, Anton
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Erstavik: Fideikommiss ur ett resursperspektiv2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    By examining the spicific structure of ownership associated with a fideikommiss, this study uses a geographic perspective to explain how Erstavik remain a rural-like area surrounded by urban development. The results based on questionnaire and literature search shows that laws and regulations for fideikommiss does not fully protect property within a fideikommiss from development. However, the consequences of the specific rules for fideikommiss shows to impede urban development within a fideikommiss over time. In addition, the function of the area as a large greenspace with high conservation values largely accessible for visitors, does show to be a likely explanation for the prolongation of Erstavik as a fideikommiss. By analyzing the results in a context of urban greenspace, ecosystem services and land use, previous studies on related topics are presented and compared with for an added scientific perspective. As a method to view Erstaviks fideikommiss from a resource perspective, the local municipality, county administration and landowner gives their view on todays' land use in Erstavik based on each respective agenda. Lastly, the varying meanings of a resource in a context of geography is briefly applied to each respective agenda.

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  • 315.
    Haeffner, Oscar
    Stockholm University, Faculty of Science, Department of Physical Geography.
    En obruten fjällmiljö och konflikten med vindkraften: En studie om rumsliga landskapspreferenser och vindkraftens påverkan på de svenska fjällen2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the Swedish mountains the government has established 13 areas, covering around 10 % of the country, as areas of undisturbed mountain regions. These areas are to be protected against activities threatening environmental and cultural values. There is also an environmental goal aiming to maintain the originality of the Swedish mountains called Storslagen fjällmiljö, in translation: A magnificent mountain landscape. These two factors are being threatened by the future plans of increasing the number of wind turbines in these areas. In this study the visual effects of the existing and not yet existing wind turbines are being examined by performing a GIS-analysis. This is analyzed based on place sensitivity and people’s relation to their surrounding landscape. The study has shown that wind turbines have a significant visual impact on the undisturbed mountain regions and that the environmental goal aiming to keep the originality of the mountains does not reach its target. However, it must be pointed out that this future change in the scenic landscape of the Swedish mountains also can be seen as something good, this depending strongly on your relationship with the landscape.

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  • 316. Hagenbo, Andreas
    et al.
    Hadden, David
    Clemmensen, Karina E.
    Grelle, Achim
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mölder, Meelis
    Ekblad, Alf
    Fransson, Petra
    Carbon use efficiency of mycorrhizal fungal mycelium increases during the growing season but decreases with forest age across a Pinus sylvestris chronosequence2019In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 107, no 6, p. 2808-2822Article in journal (Refereed)
    Abstract [en]

    In boreal forest soils, mycelium of mycorrhizal fungi is pivotal for regulating soil carbon (C) cycling and storage. The carbon use efficiency (CUE), a key parameter in C cycling models, can inform on the partitioning of C between microbial biomass, and potential soil storage, and respiration. Here, we test the dependency of mycorrhizal mycelial CUE on stand age and seasonality in managed boreal forest stands. Based on mycelial production and respiration estimates, derived from sequentially incubated ingrowth mesh bags, we estimated CUE on an ecosystem scale during a seasonal cycle and across a chronosequence of eight, 12- to 158-year-old, managed Pinus sylvestris forest stands characterized by decreasing pH and nitrogen (N) availability with increasing age. Mycelial respiration was related to total soil respiration, and by using eddy covariance flux measurements, primary production (GPP) was estimated in the 12- and 100-year-old forests, and related to mycelial respiration and CUE. As hypothesized, mycelial CUE decreased significantly with increasing forest age by c. 65%, supposedly related to a shift in mycorrhizal community composition and a metabolic adjustment reducing their own biomass N demand with declining soil N availability. Furthermore, mycelial CUE increased by a factor of five over the growing season; from 0.03 in May to 0.15 in November, and we propose that the seasonal change in CUE is regulated by a decrease in photosynthate production and temperature. The respiratory contribution of mycorrhizal mycelium ranged from 14% to 26% of total soil respiration, and was on average 17% across all sites and occasions. Synthesis. Carbon is retained more efficiently in mycorrhizal mycelium late in the growing season, when fungi have access to a more balanced C and nutrient supplies. Earlier in the growing season, at maximum host plant photosynthesis, when below-ground C availability is high in relation to N, the fungi respire excess C resulting in lower mycelial carbon use efficiency (CUE). Additionally, C is retained less efficiently in mycorrhizal fungal biomass in older forest stands characterized by more nutrient depleted soils than younger forest stands.

  • 317. Haghighi, Erfan
    et al.
    Madani, Kaveh
    Stockholm University, Faculty of Science, Department of Physical Geography. Imperial College London, UK.
    Hoekstra, Arjen Y.
    The water footprint of water conservation using shade balls in California2018In: Nature Sustainability, ISSN 2398-9629, Vol. 1, no 7, p. 358-360Article in journal (Refereed)
    Abstract [en]

    The interest in quick technologic fixes to complex water problems increases during extreme hydroclimatic events. However, past evidence shows that such fixes might be associated with unintended consequences. We revisit the idea of using shade balls in the Los Angeles reservoir to reduce evaporation during the recent drought in California, and question its sustainability by revealing the water footprint of this technologic water conservation solution.

  • 318.
    Hahn, Thomas
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Heinrup, Malena
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Lindborg, Regina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Landscape heterogeneity correlates with recreational values: a case study from Swedish agricultural landscapes and implications for policy2018In: Landscape research, ISSN 0142-6397, E-ISSN 1469-9710, Vol. 43, no 5, p. 696-707Article in journal (Refereed)
    Abstract [en]

    Agri-environmental schemes are often targeted at heterogenic landscapes to support several ecosystem services besides food production. The question is whether heterogenic landscapes also support recreation values. Previous studies suggest this but statistical analysis of the relation between heterogeneity and recreation is lacking. To assess this, we used a quantitative Landscape Heterogeneity Index (LHI), developed for biodiversity conservation. We asked five different user groups to score 12 photographs of landscapes depicting different LHI. All user groups, especially conservationists and hunters, preferred the heterogeneous landscapes and this difference was statistically significant for all groups except farmers. Accessibility, in terms of roads, had no obvious impact on the recreational value conveyed by the photos. The paper provides evidence that the recreational value amplifies biodiversity-based values of heterogeneous landscapes and argues that such landscapes also provide resilience and insurance value buffering against unexpected risks. Implications for policy are discussed.

    HIGHLIGHTS

    Recreational value was positively correlated to landscape heterogeneity.

    This correlation was statistically significant for all user groups except farmers.

    Accessibility, in terms of roads, had no obvious impact on the recreational value.

    The multi-functionality of heterogeneous agricultural landscapes including resilience and the insurance value should be better acknowledged in policy.

  • 319.
    Haking, Linn
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Peloponnesian Stalagmites and Soda Straw Stalactites as Climate Archives: Stable Isotopes in New Speleothem Material from Kapsia Cave, Peloponnese, Greece2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study presents results from stable isotope analyses of a modern stalagmite and three soda straw stalactites from Kapsia Cave, the Peloponnese, Greece. The resulting values from the stalagmite are put into context of local meteorological data, as well as previous research from Kapsia Cave. The potential for using soda straw stalactites as complementary climate archives on shorter time scales on the Peloponnese is also explored. The isotopic values in the stalagmite confirm a strong link to the amount effect on an annual scale. On a seasonal scale, variations in the isotopic signal can be detectedas a result of i.e. increased cave air temperature in summer. The stable isotope values in the soda straw stalactites largely correspond to previous isotopic measurements in Kapsia Cave. The trend of the isotopic carbon signal in two of the straws also strengthens earlier theories suggesting a link to CO2 concentrations in the external atmosphere. Soda straws are, thus, encouraged for use in future climate studies, although the sampling method should be further explored. The results of this study contribute to an increased understanding of Peloponnesian speleothems in relation to environmental processes and new insights are suggested into the use of soda straw stalactites as climate archives.

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  • 320.
    Hall, Adrian M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Binnie, Steven A.
    Sugden, David
    Dunai, Tibor J.
    Wood, Christina
    Late readvance and rapid final deglaciation of the last ice sheet in the Grampian Mountains, Scotland2016In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 31, no 8, p. 869-878Article in journal (Refereed)
    Abstract [en]

    Towards the end of the last glaciation, ice sourced from the western Grampian Mountains of Scotland flowed down Strath Spey to encroach on the northern flanks of the Cairngorm Mountains. The maximum of this late advance and its subsequent retreat is recorded by moraines, ice-marginal meltwater channels, and kame terraces that can be traced for 60 km along Strath Spey. New cosmogenic Be-10 exposure ages from moraines indicate deglaciation at 15.1 +/- 1.1 ka. This timing matches closely the recalibrated mean ages of 14.7 +/- 0.7 and 15.2 +/- 0.7 ka for the Wester Ross Readvance in the North-West Highlands. A synchronous readvance of the British-Irish Ice Sheet (BIIS) towards the end of Greenland Stadial 2a (GS-2a) (16.9-14.7 ka) is indicated. Thereafter active ice retreat from the flanks of Strath Spey was rapid, occurring within the similar to 1 ka uncertainty of the cosmogenic exposure ages. We suggest the advance followed the collapse of the marine parts of the BIIS at similar to 16 ka due to conditions of increased precipitation occurring at a time of low temperatures. The rapidity of deglaciation may reflect enhanced Fohn effects caused by the ice dome in the western Grampians.

  • 321.
    Hall, Adrian M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gillespie, M. R.
    Fracture controls on valley persistence: the Cairngorm Granite pluton, Scotland2017In: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 106, no 6, p. 2203-2219Article in journal (Refereed)
    Abstract [en]

    Valleys are remarkably persistent features in many different tectonic settings, but the reasons for this persistence are rarely explored. Here, we examine the structural controls on valleys in the Cairngorms Mountains, Scotland, part of the passive margin of the eastern North Atlantic. We consider valleys at three scales: straths, glens and headwater valleys. The structural controls on valleys in and around the Cairngorm Granite pluton were examined on satellite and aerial photographs and by field survey. Topographic lineaments, including valleys, show no consistent orientation with joint sets or with sheets of microgranite and pegmatitic granite. In this granite landscape, jointing is not a first-order control on valley development. Instead, glens and headwater valleys align closely to quartz veins and linear alteration zones (LAZs). LAZs are zones of weakness in the granite pluton in which late-stage hydrothermal alteration and hydro-fracturing have greatly reduced rock mass strength and increased permeability. LAZs, which can be kilometres long and > 700 m deep, are the dominant controls on the orientation of valleys in the Cairngorms. LAZs formed in the roof zone of the granite intrusion. Although the Cairngorm pluton was unroofed soon after emplacement, the presence of Old Red Sandstone (ORS) outliers in the terrain to the north and east indicates that the lower relief of the sub-ORS basement surface has been lowered by < 500 m. Hence, the valley patterns in and around the Cairngorms have persisted through > 1 km of vertical erosion and for 400 Myr. This valley persistence is a combined product of regionally low rates of basement exhumation and of the existence of LAZs in the Cairngorm pluton and sub-parallel Caledonide fractures in the surrounding terrain with depths that exceed 1 km.

  • 322.
    Hall, Adrian M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Merritt, Jon W.
    Connell, E. Rodger
    Hubbard, Alun
    Early and Middle Pleistocene environments, landforms and sediments in Scotland2019In: Earth and environmental science transactions of the Royal Society of Edinburgh, ISSN 1755-6910, E-ISSN 1755-6929, Vol. 110, no 1-2, p. 5-37, article id PII S1755691018000713Article in journal (Refereed)
    Abstract [en]

    This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from Scotland into the North Sea but only 4-5 advances have been identified from the terrestrial stratigraphy. Two primary modes of glaciation, mountain ice cap and full ice sheet modes, can be recognised. Different zones of glacial erosion in Scotland reflect this bimodal glaciation and the spatially and temporally variable dynamics at glacier beds. Depths of glacial erosion vary from almost zero in Buchan to hundreds of metres in glens in the western Highlands and in basins both onshore and offshore. The presence of tors and blockfields indicates repeated development of patches of cold-based, non-erosive glacier ice on summits and plateaux. In lowlands, chemical weathering continued to operate during interglacials, but gruss-type saprolites are mainly of Pliocene to Early Pleistocene age. The Middle Pleistocene terrestrial stratigraphic record in Scotland, whilst fragmentary and poorly dated, provides important and accessible evidence of changing glacial, periglacial and interglacial environments over at least three stadial-interstadial-interglacial cycles. The distributions of blockfields and tors and the erratic contents of glacial sediments indicate that the configuration, thermal regime and pattern of ice flow during MIS 6 were broadly comparable to those of the last ice sheet. Improved control over the ages of Early and Middle Pleistocene sediments, soils and saprolites and on long-term rates of weathering and erosion, combined with information on palaeoenvironments, ice extent and sea level, will in future allow development and testing of new models of Pleistocene tectonics, isostasy, sea-level change and ice sheet dynamics in Scotland.

  • 323.
    Hall, Adrian M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Riding, James B.
    The last glaciation in Caithness, Scotland: revised till stratigraphy and ice-flow paths indicate multiple ice flow phases2016In: Scottish Journal of Geology, ISSN 0036-9276, E-ISSN 2041-4951, Vol. 52, p. 77-89Article in journal (Refereed)
    Abstract [en]

    This paper reviews existing information on the last glaciation of Caithness and presents new evidence for additional till units and for long distance ice-flow paths based on till palynomorphs, indicator erratics and striae. Early, radial expansion of Northern Highland ice probably occurred at 31 - 29 ka. After ice withdrawal from the north coast, Moray Firth ice returned before a second withdrawal. Thereafter Moray Firth ice advanced to limits close to the Atlantic shelf edge between 21 and 18 ka. Deglaciation of hill summits was completed by 18.4 - 17.8 ka but the low ground south of Wick only became ice free after 16.5 ka. Recognition of these multiple ice-flow events is consistent with the dynamic behaviour of the last ice sheet exhibited in mathematical simulations. The event sequence differs, however, from nineteenth century and recent two-stage flow set reconstructions as each main flow set is shown to represent multiple events following similar paths but under different ice sheet configurations. Various configurations allow ice to flow northwards across Caithness and so remove any requirement for the Fennoscandian Ice Sheet to directly block and divert the outflow of ice from the Moray Firth during the last glaciation.

  • 324.
    Hall, Adrian M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Riding, James B.
    Brown, John F.
    The last glaciation in Orkney, Scotland: glacial stratigraphy, event sequence and flow paths2016In: Scottish Journal of Geology, ISSN 0036-9276, E-ISSN 2041-4951, Vol. 52, p. 90-101Article in journal (Refereed)
    Abstract [en]

    Three separate till units are recognized on Orkney deposited during the last ice sheet glaciation: the Digger, Scara Taing and Quendal Till members. The Digger Till records an ice advance fromthe south that extended on to the Atlantic shelf. The Scara Taing Till records a later period of full ice cover when ice moved from the SE out of the Moray Firth and reached Last Glacial Maximum (LGM) limits on the shelf edge. The Quendal Till records a late phase of ice sheet flow from the SE to limits c. 20 km west of Orkney. No till unit or flow set has been identified to confirm the presence of a local ice cap on southern Orkney during the last glaciation. Whilst the blocking presence of the Fennoscandian Ice Sheet (FIS) and the Shetland Ice Cap may have contributed to the deflection of ice flow over Orkney, similar flow patterns also occurred before and after the LGM. Scandinavian erratics on northern Orkney are probably reworked and provide no direct support for the passage of the FIS. Middle to Late Carboniferous palynomorphs found in tills in eastern Orkney may have been reworked from nearby Permian mudstones.

  • 325.
    Hall, Adrian M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Sarala, Pertti
    Ebert, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Late Cenozoic deep weathering patterns on the Fennoscandian shield in northern Finland: A window on ice sheet bed conditions at the onset of Northern Hemisphere glaciation2015In: Geomorphology, ISSN 0169-555X, E-ISSN 1872-695X, Vol. 246, p. 472-488Article in journal (Refereed)
    Abstract [en]

    The nature of the regolith that existed on the shields of the Northern Hemisphere at the onset of ice sheet glaciation is poorly constrained. In this paper, we provide the first detailed account of an exceptionally preserved, deeply weathered late Neogene landscape in the ice sheet divide zone in northern Finland. We mine data sets of drilling and pitting records gathered by the Geological Survey of Finland to reconstruct regional preglacial deep weathering patterns within a GIS framework. Using a large geochemical data set, we give standardised descriptions of saprolite geochemistry using a variant of the Weathering Index of Parker (WIP) as a proxy to assess the intensity of weathering. We also focus on mineral prospects and mines with dense pit and borehole data coverage in order to identify links between geology, topography, and weathering.

    Geology is closely linked to topography on the preglacial shield landscape of northern Finland and both factors influence weathering patterns. Upstanding, resistant granulite, granite, gabbro, metabasalt, and quartzite rocks were associated with fresh rock outcrops, including tors, or with thin (< 5 m) grusses. Plains developed across less resistant biotite gneisses, greenstones, and belts of alternating rock types were mainly weathered to thick (10–20 m) grusses with WIPfines values above 3000 and 4000. Beneath valley floors developed along mineralised shear and fracture zones, weathering penetrated locally to depths of > 50 m and included intensely weathered kaolinitic clays with WIPfines values below 1000.

    Late Neogene weathering profiles were varied in character. Tripartite clay–gruss–saprock profiles occur only in limited areas. Bipartite gruss–saprock profiles were widespread, with saprock thicknesses of > 10 m. Weathering profiles included two discontinuities in texture, materials and resistance to erosion, between saprolite and saprock and between saprock and rock. Limited core recovery when drilling below the soil base in mixed rocks of the Tana Belt indicates that weathering locally penetrated deep below upper fresh rock layers. Such deep-seated weathered bands in rock represent a third set of discontinuities. Incipient weathering and supergene mineralisation also extended to depths of > 100 m in mineralised fracture zones. The thin weathering crusts found extensively beneath till may represent types of early or middle Pleistocene palaeosols.

    We confirm that glacial erosion has been very limited (< 20 m) in northern Finland and has been widely restricted to the partial stripping of saprolith. The Fennoscandian Ice Sheet in this ice-divide zone remained cold-based and unerosive throughout the Pleistocene. The large-scale shield geomorphology developed before glaciation and is a product of differential weathering and erosion acting on diverse rock types and structures through the Neogene. The first ice sheets did not advance across planar, uniformly soft, deeply kaolinised beds as proposed in recent models of the Laurentide ice sheet. Instead, in northern Finland, the shield topography comprised broad plains and valleys with isolated hills and hill masses, with a relative relief of several hundred metres. Weathered rock was restricted in its distribution and thickness and provided diverse bed materials for ice sheets, including rock, broken saprock, permeable gruss, and linear zones of impermeable clay, with multiple discontinuities. Glacial erosion and local glacial transport led to widespread incorporation of this saprolith material into tills.

  • 326.
    Hall, Adrian Malcolm
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Phanerozoic denudation across the Kola Peninsula, northwest Russia: implications for long term stability of Precambrian shield margins2015In: Norsk Geologisk Tidsskrift, ISSN 0029-196x, Vol. 95, no 2, p. 153-169Article in journal (Refereed)
    Abstract [en]

    Contrasting views exist on the stability of the Earth’s shield regions over the last 1 Ga that have major implications for reconstructing erosion patterns on shields and the supply of sediment to intra-cratonic and marginal basins. This paper explores Phanerozoic denudation rates and patterns on the northern part of the Fennoscandian Shield in the Kola Peninsula, Northwest Russia. This shield region was intruded by magmatic rocks of the Kola Alkaline Province (KAP) in the Devonian and Early Carboniferous. The KAP comprises a varied suite of alkali–ultramafic plutonic and hypabyssal intrusions, diatremes and dykes that was emplaced at various depths in the crust and allows assessment of depths and rates of erosion during and since the KAP magmatic episode. Further evidence of long-term denudation is provided by Mesoproterozoic and Neoproterozoic cover rocks found around the margins of the Kola Peninsula and in the White Sea. The burial and exhumation history is compared to available Apatite Fission Track (AFT) data for the Kola Peninsula and adjacent areas. Post-Devonian denudation rates on the shield rocks of the Kola Peninsula have varied in space and time. Around the periphery of the Kola Peninsula, low long-term denudation of shield rocks is indicated by the survival of Riphean cover rocks and Late Devonian lavas, kimberlite crater facies and near-surface emplacement of dykes. In contrast, in the main belts of KAP intrusions, 4–6 km of rock was removed in response to doming between 460 and 360 Ma. Deep denudation is indicated by the emplacement depths of alkaline intrusions and Phoscorite–Carbonatite pipes (PCPs). Erosion on the Kola Peninsula since 360 Ma has been far more limited. Extensive, shallow, late-stage magmatism associated with PCPs, dykes and the large alkaline intrusions in the KAP indicates that erosion depths nowhere exceeded 2 km. Post-Devonian denudation has removed <1 km of rock from the margins of the Kola Peninsula and from the backslope of the Saariselkä–Karelia scarp in northern Finland. AFT data point to an important phase of erosion in the early Mesozoic but depths of unroofing of 3–5 km based on AFT cooling ages for this later phase are in conflict with the evidence of lesser erosion provided by the late-stage KAP intrusions and also require unrealistic depths of former Devonian to Triassic cover rocks. Mean denudation rates were greatest (up to 40 m/Myr) during the KAP magmatic phase. Post-Devonian rates across the Kola Peninsula and adjacent shield areas were much lower (<3–6 m/Myr) and are compatible with low long-term denudation rates for other cratons. Further resolution of longterm denudation patterns and rates on the Kola Peninsula requires the application of low-temperature thermochronometry, detailed examination of the regional geomorphology and firmer dating of ancient weathering episodes.

  • 327.
    Halldén, Tom Halldén
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Measuring coastal erosion along the coast of Ystad municipality using PSInSAR and SBAS2017Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    In this study the use of two radar interferometry methods, PSInSAR and SBAS, were tested as tools for measuring coastal erosion. If successful it would have allowed for measuring coastal erosion as a function of material lost. The study area used was Ystad municipality, in southern Sweden.

    Radar data for the study was provided by the ESA, the European space agency, from their ERS-2 and ENVISAT satellites, spanning the period 1998-2005.

    Unfortunately, even after many different configurations of settings were tested, the results indicated that both methods are very unsuited for use in rural areas such as Ystad, whether for measuring coastal erosion or otherwise. Both methods had severe problems achieving significant coverage after low coherence areas were masked out, and PSInSAR suffered from several anomalies. This is likely due to the highly vegetated nature of the landscape, which results in low coherence through temporal decorrelation.

    Of the two methods SBAS showed the most promise, but not nearly enough to be considereduseful.

    It is, based on the scientific literature, possible that simpler interferometry methods might have been more useful. This, and other possible ways to improve the results is something that this study discusses at length.

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  • 328.
    Hallström, Ellinor
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Payment for Ecosystem Services (PES) and Water Resource Management of the tropical mountain ecosystem páramo: A case study in the northern parts of Ecuador2017Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Latin America has pioneered the concept of Payment for Ecosystem Services (PES) as a strategy to improve the management of ecosystem services. Ecuador is not an exception, where many PES schemes have been implemented to protect the tropical mountain ecosystem “páramo” and the water resources these areas are generating for downstream societies. A successful PES scheme needs to achieve both targeted bio-physical objectives and at the same time benefit local conditions while not risking to sacrifice the local demand for ecosystem services. This balance is explored here in a case study focusing on the Río Grande watershed in the highlands in the northern parts of Ecuador by exemplifying community participation in the public PES scheme Socio Bosque (PSB) starting in 2009. The water resource distribution (precipitation, discharge, actual evapotranspiration and potential evapotranspiration) in the watershed was evaluated over the last decades. The local perception of the PSB and its impacts on local and regional water resources were also studied and characterized. The results showed that the annual discharge in the Río Grande watershed has decreased significantly from 1967-2014 and that the annual discharge was significantly lower between 1997-2015 compared to 1979-1997. Since precipitation did not decrease significantly during this period, the changes of the annual discharge are more likely depended on factors controlling the seasonal distribution of discharge and evapotranspiration in the watershed. For example, large scale land use changes coupled with a significantly warmer climate in the region could be a possible driver. Of course, this would not exclude other important factors such as changes in water demand and the supply of freshwater from the Río Grande watershed to downstream societies. The results of this case study showed that it is likely too early to see any impacts in the water balance components as a direct response to the implemented PSB scheme. Clearly, this motivates a need for continued evaluation of the local perception and the water resources to ensure that the need and demand for ecosystem services in a long-term perspective are maintained.

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  • 329. Hamel, Perrine
    et al.
    Riveros-Iregui, Diego
    Ballari, Daniela
    Browning, Trevor
    Célleri, Rolando
    Chandler, David
    Chun, Kwok Pan
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jacobs, Suzanne
    Jasechko, Scott
    Johnson, Mark
    Krishnaswamy, Jagdish
    Poca, María
    Pompeu, Patrícia Vieira
    Rocha, Humberto
    Watershed services in the humid tropics: Opportunities from recent advances in ecohydrology2018In: Ecohydrology, ISSN 1936-0584, E-ISSN 1936-0592, Vol. 11, no 3, article id e1921Article in journal (Refereed)
    Abstract [en]

    In response to increasing pressures on water resources, watershed services management programs are implemented throughout the tropics. These programs aim to promote land management activities that enhance the quantity and quality of water available to local communities. The success of these programs hinges on our ability to (a) understand the impacts of watershed interventions on ecohydrology; (b) model these impacts and design efficient management programs; and (c) develop strategies to overcome barriers to practical policy development, including resource limitations or the absence of baseline data. In this paper, we review opportunities in ecohydrological science that will help address these three challenges. The opportunities are grouped into measurement techniques, modelling approaches, and access to resources in our hyperconnected world. We then assess management implications of both the knowledge gaps and the new research developments related to the effect of land management. Overall, we stress the importance of policy-relevant knowledge for implementing efficient and equitable watershed services programs in the tropics.

  • 330.
    Hamré, Moa
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mapping glacier change in Sweden between the end of ‘Little Ice Age’ and 2008 with orthophotos and a Digital Elevation Model2015Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
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  • 331.
    Han, Zixuan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Lanzhou University, China.
    Su, Tao
    Zhang, Qiong
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wen, Qin
    Feng, Guolin
    Thermodynamic and dynamic effects of increased moisture sources over the Tropical Indian Ocean in recent decades2019In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 53, no 11, p. 7081-7096Article in journal (Refereed)
    Abstract [en]

    In the present work, the mechanisms for the changes in moisture sources (evaporation minus precipitation; EmP) during boreal summer (May-September) are explored over the tropical Indian Ocean during 1979-2016. We apply a moisture budget analysis to quantify the thermodynamic and dynamic effects. Our results show that the EmP in the tropical central-eastern and southwestern Indian Oceans experienced significant increasing trends during boreal summer. The increased EmP in the tropical central-eastern Indian Ocean is due to the enhanced dynamic divergence (account for approximately 51%), while a stronger dynamic advection contributes more moisture supply to the southwestern Indian Ocean (account for approximately 34%). We find that during recent decades, the enhanced east-west thermal gradient in the Pacific strengthens the Walker Circulation, which leads to a westward shift in convection over the Indian Ocean warm pool, resulting in weakened convection and ascent over the tropical central-eastern Indian Ocean. The weakened convection leads to an anomalous low-level atmospheric divergent circulation, which intensifies the dynamic divergence contributing to the enhanced EmP over the tropical central-eastern Indian Ocean. Additionally, the warming climate during recent decades also increases the land-sea thermal contrast in the vicinity of the Indian Ocean, which enhances the southeastern wind in the low-level troposphere and leads to an enhanced EmP over the southwestern Indian Ocean.

  • 332.
    Hanses, Lena
    Stockholm University, Faculty of Science, Department of Physical Geography.
    I never tried the swings before: Perspectives on urban greenspace from children with profound intellectual and multiple disabilities2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To achieve the United Nations Sustainable Development Goal 11.7 aiming to create inclusiveand accessible greenspaces, there is need to involve children with profound intellectual andmultiple disabilities in research and planning practices. The aim of this study is to explore whatexperiences of accessibility children with profound intellectual and multiple disabilities haveof greenspace. Through the qualitative method of go along interviews using augmentative andalternative communication, such as pictures and sign language, children provide their opinionsabout the public park Långbroparken in southern Stockholm, Sweden. Their experiences areanalysed through the framework of environmental justice, exploring fair distribution,recognition, capabilities and functioning. The findings demonstrate that children with profoundintellectual and multiple disabilities can indeed be included in research practices throughadapted interview situations. Either the researcher needs to be skilled and experienced inalternative and augmentative communication, and preferably have previous relations with thechildren, or be able to cooperate with someone who has such abilities and connections.Individual experiences of physical and social accessibility in the park create feelings of bothoutsideness and immersing oneself into nature and highlight the interaction of person andenvironment. In conclusion, children with profound intellectual and multiple disabilities holdvaluable explanations and experiences of what constitutes inclusive and accessible greenspacesand their perspectives are required to fulfil targets such as the United Nations SustainableDevelopment Goal 11.7.

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  • 333.
    Hansson, Lina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Concentrations and riverine massflows of geothermal arsenic.: Case study: Jemez River, NM, USA2016Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Geothermal arsenic (As) and its inorganic species transformation in river systems are of global concern, since As has a potential negative impact on human health and ecosystems. Periods of increased precipitation may change As concentrations and As partitioning in streams, due to elevated water tables, increased runoff generation, dilution, and interactions with sediment.In this study we investigate hydrological conditions of Jemez River, located along the Jemez fault in NM, USA, during the monsoon months June, July and August of 2015. We aim at determining how different hydrological conditions in the Jemez River during the monsoon months might affect the concentrations and riverine mass flows of geothermally derived (total) As and As III discharging in a travertine- and hot spring area called Soda Dam.

    Water and sediment from the river and hot springs sites, as well as streamflow measurements along a 22 km river reach were collected. The chemical composition of water and sediment was determined using Inductively Coupled Plasma-Optical Emission Spectrometry/Mass Spectrometry (ICP-OES/MS); and Ion Chromatography (IC) as well as a High Performance Liquid Chromatograph (HPLC) coupled to an ICP-MS for further water analysis. Discharge and mass flows as well as element inputs and outputs to/from Soda Dam was computed.

    The measurement months were characterized by a median discharge of 1642 L/s. During the measurement campaigns peak flows occurred with discharges of 2.5×104 to 6.1×104 L/s during the measurement campaigns. Arsenic concentrations were between 1.3 and 107 μg/L in river water, between 167.3 and 6707 μg/L in hot spring waters, and between 0.37 and 13.1 μg/kg in river bed sediment. Arsenic III was found in hot springs water and river water. Infiltration and subsurface flows induced by fault-associated fractures and permeability structures were found to be likely to divert water at Soda Dam, as reflected in large discharge differences along the reach (470 to 1305 L/s). These flows also had an impact on As concentrations in riverine and hot spring water since they mobilize As from bedrock and sediment. Changing mass flows of As can only in a few cases be explained by dilution processes by Jemez River, which has previously been assumed to be the main control on As mass flows along the stretch. Instead, our findings are likely to reflect changes in chemical composition of the mixed geothermal waters discharging at Soda Dam, due to changing mixing ratios of ground waters of different compositions. The present study hence provides a refined interpretation of the hydrological pathways in Soda Dam and Jemez River, and calls for more discharge and geochemical investigations during a longer study period, to properly investigate the driving forces behind the fate of the As from geothermal fluids. 

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  • 334.
    Haraldsson, Jenny
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Klimatvariationer underholocen rekonstrueradegenom humifieringsanalys av entorvmosse i Värmland; dateratmed hjälp av tefrokronologi2014Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    SammanfattningKlaxsjömossen i Värmland har undersökts för tefra och humifiering i syfte att åldersbestämma klimatvariationer i Värmland under holocen. Studien har genomförts på en borrkärna från en torvmosse och analyserats med hjälp av tefrokronologi och humifieringsanalys samt elektronmikroskop. Det har identifierats fem tefra-lager i mossen på djupen: 5-10 cm, 60-65 cm, 315-320 cm, 350-355 cm och 390-395 cm vilket enligt ålder-djup profilen motsvarar de ungefärliga åldrarna 130, 390, 3050, 3720 och 4260 år BP. Efter kemisk undersökning i elektronmikroskop har dessa tefralager identifierats till spår från vulkanutbrotten Hekla 4 på 395 cm djup, Kebister på 350 cm djup, Hekla 3 på 315 cm djup och Askja AD 1875 på 5-10 cm djup. Tefrokronologin har bidragit till tidsmarkörer som ligger till grund för klimatjämförelsen. Genom humifieringsanalysen har torvens förmultningsgrad undersökts och jämförts med kringliggande mossar och andra klimatarkiv. Vissa korrelationer har upptäcks vilket tyder på regionala klimatsignaturer, andra tyder på lokala förhållanden i mossen.

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  • 335. Harden, Jennifer W.
    et al.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography. Stanford University, USA.
    Ahlström, Anders
    Blankinship, Joseph C.
    Bond-Lamberty, Ben
    Lawrence, Corey R.
    Loisel, Julie
    Malhotra, Avni
    Jackson, Robert B.
    Ogle, Stephen
    Phillips, Claire
    Ryals, Rebecca
    Todd-Brown, Katherine
    Vargas, Rodrigo
    Vergara, Sintana E.
    Cotrufo, M. Francesca
    Keiluweit, Marco
    Heckman, Katherine A.
    Crow, Susan E.
    Silver, Whendee L.
    DeLonge, Marcia
    Nave, Lucas E.
    Networking our science to characterize the state, vulnerabilities, and management opportunities of soil organic matter2018In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 24, no 2, p. e705-e718Article in journal (Refereed)
    Abstract [en]

    Soil organic matter (SOM) supports the Earth's ability to sustain terrestrial ecosystems, provide food and fiber, and retains the largest pool of actively cycling carbon. Over 75% of the soil organic carbon (SOC) in the top meter of soil is directly affected by human land use. Large land areas have lost SOC as a result of land use practices, yet there are compensatory opportunities to enhance productivity and SOC storage in degraded lands through improved management practices. Large areas with and without intentional management are also being subjected to rapid changes in climate, making many SOC stocks vulnerable to losses by decomposition or disturbance. In order to quantify potential SOC losses or sequestration at field, regional, and global scales, measurements for detecting changes in SOC are needed. Such measurements and soil-management best practices should be based on well established and emerging scientific understanding of processes of C stabilization and destabilization over various timescales, soil types, and spatial scales. As newly engaged members of the International Soil Carbon Network, we have identified gaps in data, modeling, and communication that underscore the need for an open, shared network to frame and guide the study of SOM and SOC and their management for sustained production and climate regulation.

  • 336.
    Harney, Pawel
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Evaluation of the use of a Dynamic versus a Simple Correction Model to correct for systematic errors in Swedish Precipitation Data2016Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    A Dynamic Correction Model (DCM) was implemented to correct daily precipitation data from the network of precipitation gauges hosted by the Swedish Meteorological and Hydrological Institute (SMHI). The goal was to determine whether the DCM could be used to improve estimates of the influence of systematic errors on precipitation observations compared to a previous assessment made on the SMHI dataset using a Simple Correction Model (SCM). While the SCM in question only takes into account station exposure and temperature, reflecting the yearly average gauge level wind speed and the monthly average probability of snow respectively, the DCM would take into account sub-daily and daily observations of precipitation intensity, wind speed and temperature to correct precipitation according to the observed conditions at the time of the precipitation event. DCM corrections were performed on precipitation data from 165 stations throughout Sweden.The long term average result of aggregating daily DCM corrected precipitation was compared to the previous SCM correction for 24 stations while the daily corrected solid precipitation was evaluated against snow depth observations for 59 stations throughout Sweden.Since the systematic errors almost exclusively cause an underestimation of ground true precipitation the correction was expected to produce an increase in total precipitation. Since this undercatch is greater during solid precipitation, a pattern of higher correction was expected to be found in winter months compared to summer months, a pattern which could be expected to be stronger the further north in the country one looked. Furthermore, superimposed on this, areas which are more exposed to wind can be expected to require a larger correction due to the undercatch being also strongly correlated to wind speed. At the sub monthly time scale a variation in the undercatch could be expected when using the DCM with increased corrections required on days when precipitation falls as snow and on days when wind speeds are higher.For the comparison with previous SCM estimates the expectation was that long term totals (30 year average corrected precipitation) would be similar if the two methods are assumed to be equally valid. The DCM was further expected to improve correlations between newly fallen snow and change in snow depth.While the qualitative patterns in the corrections found met the expectations, large differences in the quantitative results of using the two different methods were found; the DCM had a tendency to overcorrect compared to the SCM, especially for the more exposed stations. This calls into question the assumption that both methods are equally valid and differ only in their temporal resolution, and further raises the question which if any of the methods is more valid and why. The evaluation of DCM corrected solid precipitation using snow depth showed a decrease in the correlation between precipitation and change in snow depth which was contrary to expectations. The greatest uncertainty in the DCM was attributed to the methods for assessing gauge level wind speeds.

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  • 337. Harpold, A. A.
    et al.
    Marshall, J. A.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Barnhart, T. B.
    Fisher, B. A.
    Donovan, M.
    Brubaker, K. M.
    Crosby, C. J.
    Glenn, N. F.
    Glennie, C. L.
    Kirchner, P. B.
    Lam, Norris
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mankoff, K. D.
    McCreight, J. L.
    Molotch, N. P.
    Musselman, K. N.
    Pelletier, J.
    Russo, T.
    Sangireddy, H.
    Sjöberg, Ylva
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Swetnam, T.
    West, N.
    Laser vision: lidar as a transformative tool to advance critical zone science2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 6, p. 2881-2897Article in journal (Refereed)
    Abstract [en]

    Observation and quantification of the Earth's surface is undergoing a revolutionary change due to the increased spatial resolution and extent afforded by light detection and ranging (lidar) technology. As a consequence, lidar-derived information has led to fundamental discoveries within the individual disciplines of geomorphology, hydrology, and ecology. These disciplines form the cornerstones of critical zone (CZ) science, where researchers study how interactions among the geosphere, hydrosphere, and biosphere shape and maintain the 'zone of life', which extends from the top of unweathered bedrock to the top of the vegetation canopy. Fundamental to CZ science is the development of transdisciplinary theories and tools that transcend disciplines and inform other's work, capture new levels of complexity, and create new intellectual outcomes and spaces. Researchers are just beginning to use lidar data sets to answer synergistic, transdisciplinary questions in CZ science, such as how CZ processes co-evolve over long timescales and interact over shorter timescales to create thresholds, shifts in states and fluxes of water, energy, and carbon. The objective of this review is to elucidate the transformative potential of lidar for CZ science to simultaneously allow for quantification of topographic, vegetative, and hydrological processes. A review of 147 peer-reviewed lidar studies highlights a lack of lidar applications for CZ studies as 38 % of the studies were focused in geomorphology, 18 % in hydrology, 32 % in ecology, and the remaining 12 % had an interdisciplinary focus. A handful of exemplar transdisciplinary studies demonstrate lidar data sets that are well-integrated with other observations can lead to fundamental advances in CZ science, such as identification of feedbacks between hydrological and ecological processes over hillslope scales and the synergistic co-evolution of landscape-scale CZ structure due to interactions amongst carbon, energy, and water cycles. We propose that using lidar to its full potential will require numerous advances, including new and more powerful open-source processing tools, exploiting new lidar acquisition technologies, and improved integration with physically based models and complementary in situ and remote-sensing observations. We provide a 5-year vision that advocates for the expanded use of lidar data sets and highlights subsequent potential to advance the state of CZ science.

  • 338. Hartl-Meier, C. T. M.
    et al.
    Büntgen, U.
    Smerdon, J. E.
    Zorita, E.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, UK; Navarino Environmental Observatory, Greece.
    Charpentier Ljungqvist, Fredrik
    Stockholm University, Faculty of Humanities, Department of History.
    Schneider, L.
    Esper, J.
    Temperature Covariance in Tree Ring Reconstructions and Model Simulations Over the Past Millennium2017In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 18, p. 9458-9469Article in journal (Refereed)
    Abstract [en]

    Spatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multiproxy-based reconstructions. Here we use tree ring-based temperature reconstructions and state-of-the-art climate model simulations to assess temporal changes in Northern Hemisphere intercontinental temperature covariance during the last 1000 years. Tree ring-only approaches reveal stronger agreement with model simulations compared to multiproxy networks. Although simulated temperatures exhibit a substantial spread among individual models, intercontinental temperature coherency is mainly driven by the cooling of large volcanic eruptions in 1257, 1452, 1600, and 1815 Common Era. The coherence of these synchronizing events appears to be elevated in several climate simulations relative to their own unforced covariance baselines and in comparison to the proxy reconstructions. This suggests that some models likely overestimate the amplitude of abrupt summer cooling in response to volcanic eruptions, particularly at larger spatial scales.

  • 339. Hasper, Thomas B.
    et al.
    Wallin, Göran
    Lamba, Shubhangi
    Hall, Marianne
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Laudon, Hjalmar
    Linder, Sune
    Medhurst, Jane L.
    Räntfors, Mats
    Sigurdsson, Bjarni D.
    Uddling, Johan
    Water use by Swedish boreal forests in a changing climate2016In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 30, no 5, p. 690-699Article in journal (Refereed)
    Abstract [en]

    1. The rising levels of atmospheric carbon dioxide concentration ([CO2]) and temperature have the potential to substantially affect the terrestrial water and energy balance by altering the stomatal conductance and transpiration of trees. 2. Many models assume decreases in stomatal conductance and plant water use under rising [CO2], which has been used as a plausible explanation for the positive global trend in river run-off over the past century. Plant water use is, however, also affected by changes in temperature, precipitation and land use, and there is yet no consensus about the contribution of different drivers to temporal trends of evapotranspiration (ET) and river run-off. 3. In this study, we assessed water-use responses to climate change by using both long-term monitoring and experimental data in Swedish boreal forests. Historical trends and patterns in ET of large-scale boreal landscapes were determined using climate and run-off data from the past 50 years, while explicit tree water-use responses to elevated [CO2] and/or air temperature were examined in a whole-tree chamber experiment using mature Norway spruce (Picea abies (L.) Karst.) trees. 4. The results demonstrated that ET estimated from water budgets at the catchment scale increased by 18% over the past 50 years while run-off did not significantly change. The increase in ET was related to increasing precipitation and a steady increase in forest standing biomass over time. The whole-tree chamber experiment showed that Norway spruce trees did not save water under elevated [CO2] and that experimentally elevated air temperature did not increase transpiration as decreased stomatal conductance cancelled the effect of higher vapour pressure deficit in warmed air. 5. Our findings have important implications for projections of future water use of European boreal coniferous forests, indicating that changes in precipitation and standing biomass are more important than the effects of elevated [CO2] or temperature on transpiration rates.

  • 340. Hedblom, M.
    et al.
    Lindberg, F.
    Vogel, Emanuel
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wissman, J.
    Ahrné, K.
    Estimating urban lawn cover in space and time: Case studies in three Swedish cities2017In: Urban Ecosystems, ISSN 1083-8155, E-ISSN 1573-1642, Vol. 20, no 5, p. 1109-1119Article in journal (Refereed)
    Abstract [en]

    Lawns are considered monocultures and lesser contributors to sustainability than diverse nature but are still a dominating green area feature and an important cultural phenomenon in cities. Lawns have esthetical values, provide playground, are potential habitat for species, contribute to carbon sequestration and water infiltration, but also increase pesticides, fertilization, aremonocultures and costly to manage at the same time. To evaluate the potential impact of lawns, whether positive or negative, it is of interest to estimate the total lawn cover in cities and its change over time. This is not a straightforward process, e.g., because many lawns are small and covered by trees. In this study we review the existing literature of lawn cover in cities and the different methodologies used for cover estimation. We found both pros and cons with NDVI and LiDAR data as well as manually interpreted aerial photos. The total cover of lawns in three case study cities was estimated to 22.5%. By extrapolating these percentages to all Swedish cities lawn cover was estimated to 2589 km(2) (0.6% of the terrestrial surface). The approximated total municipal management cost of lawns in all Swedish cities was 910,000,000 USD/year. During 50 years lawn area almost doubled in relative cover and 56% of them were continuously managed. Since lawns constitute large parts of the urban greenery and are costly to manage it is highly relevant to consider their social, ecological and cultural value compared to alternatives, e.g., meadows with less intensive management.

  • 341.
    Hedenborg, Amanda
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Grundvattenmodellering och föroreningstransport från en rullstensås med artificiell grundvattenbildning2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Groundwater is an important natural resource in Sweden due to almost 50 % of the produced drinking water origins from groundwater, 50 % of the groundwater is artificially made. Artificial recharge is necessary in some areas in Sweden to enable enough groundwater extraction for the drinking water supply. Artificial recharge will affect the groundwater levels in the system. The infiltration of water can also affect the spread of pollution in the area. The effect of pollution spreading is due to the change in available oxygen in the system. When infiltrating water, the soil can go from anaerobic- to aerobic conditions, which in turn can cause mobilization of pollutants. This master project was carried out in collaboration with the consultancy company WSP. In this thesis, an esker assessed as suitable for artificial recharge from a hydrogeological point of view, is investigated regarding the contamination spread. Stockholm vatten och avlopp (SVOA) is investigating the possibilities for producing drinking water by artificial recharge in the esker. The area has been identified as a potential hazardous area by the Swedish environmental protection agency and increased levels of zinc, lead and copper have been found in the soil. The aim with this project is to investigate how zinc, lead and copper could spread in the groundwater for the current situation. This project also aims to investigate how the artificial recharge would affect the groundwater levels in the system as well as the effect of the spread of zinc, lead and copper regarding the mass transport, transportation time and the contaminant plume. A hydrogeological model was created in MODFLOW where the effect of infiltration was simulated. Models for groundwater transport as well as mass transport was created in MODPATH respectively in MT3DMS. The hydrogeological model´s Normalized root mean square (nRMS) was 7,4 % and the maximal residual between observed and simulated groundwater levels was 0, 16 meters. Two different scenarios for artificial recharge were investigated, one called pilotförsöket and the other called fullskaleanläggningen. For the pilotförsöket was 100 L/s infiltrated and for fullskaleanläggningen was 280 L/s infiltrated, the amount of extracted groundwater was assumed to be equal as the amount of infiltrated surface water. The simulations were indicating that the groundwater levels could rise up to 7 meters locally around the infiltration area. The groundwater levels closer to the extraction wells could decrease by 4 meters in pilotförsöket and decrease by 10-15 meters in fullskaleanläggningen. The simulations of zinc, copper and lead in the infiltration area, are indicating an increase in maximal concentration as well as an increase for the plume of contaminants as a result of infiltration. The maximal concentrations in the simulations of pilotförsöket were found to be in the following ranges 4x10-5 to 2,8x10-8 mg/L for lead; 8 x10-4 to 2,5x10-6 mg/L for copper and 0,012 to 9x10-4 mg/L for zinc. Fullskaleanläggningen resulted in the highest concentrations of the simulated scenarios. The following ranges were observed in the simulations of fullskaleanläggningen 4,5x10-5 to 4x10-8 mg/L for lead; 0,014 till 2,5x10-6 mg/L for copper, and 0,035 till 3x10-3 mg/L for zinc. The plume of contaminants was observed to increase with an increasing amount of infiltrated water. During the simulation period of 10 years, the simulation implies that zinc, copper and lead mainly will be transported close to the infiltration area. The results for simulations in all scenarios indicate that the plume of contaminant will not reach the extraction wells. These results can be due to longer transportation times than 10 years, as well as that the increase volume of water in the system will dilute the levels of metals. This master project indicates that the artificial recharge in the area will affect the groundwater levels in the system. Due to the change in groundwater levels can also the spread of zinc, copper and lead increase in magnitude and in size. This master project also indicates that zinc, copper and lead would not reach the extraction wells in high levels within a 10 years period. The simulations indicate that the area could be appropriate to use for artificial recharge, when considering zinc, copper and lead. This assessment is only based on the simulations of the mass transport of zinc, copper and lead and with the assumption that the contaminated soil would be excavated if an infiltration area is built. Even though the simulations indicate that the area could be appropriate. Other pollutants that was found, but not simulated, at increased levels could have a different transportation time as well as mass transport from the infiltration area. Regarding the age of the landfill it is likely in the methanogenic phase and leaching of contaminants could already have happened decades ago. With these two aspects in mind, my recommendation is that more investigations are made regarding the spread of other pollutants as well as the level of zinc, lead and copper in the groundwater closer to the extraction wells.

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  • 342.
    Helanow, Christian
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Basal boundary conditions, stability and verification in glaciological numerical models2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To increase our understanding of how ice sheets and glaciers interact with the climate system, numerical models have become an indispensable tool. However, the complexity of these systems and the natural limitation in computational power is reflected in the simplifications of the represented processes and the spatial and temporal resolution of the models. Whether the effect of these limitations is acceptable or not, can be assessed by theoretical considerations and by validating the output of the models against real world data. Equally important is to verify if the numerical implementation and computational method accurately represent the mathematical description of the processes intended to be simulated. This thesis concerns a set of numerical models used in the field of glaciology, how these are applied and how they relate to other study areas in the same field.

    The dynamical flow of glaciers, which can be described by a set of non-linear partial differential equations called the Full Stokes equations, is simulated using the finite element method. To reduce the computational cost of the method significantly, it is common to lower the order of the used elements. This results in a loss of stability of the method, but can be remedied by the use of stabilization methods. By numerically studying different stabilization methods and evaluating their suitability, this work contributes to constraining the values of stabilization parameters to be used in ice sheet simulations. Erroneous choices of parameters can lead to oscillations of surface velocities, which affects the long term behavior of the free-surface ice and as a result can have a negative impact on the accuracy of the simulated mass balance of ice sheets.

    The amount of basal sliding is an important component that affects the overall dynamics of the ice. A part of this thesis considers different implementations of the basal impenetrability condition that accompanies basal sliding, and shows that methods used in literature can lead to a difference in velocity of 1% to 5% between the considered methods.

    The subglacial hydrological system directly influences the glacier's ability to slide and therefore affects the velocity distribution of the ice. The topology and dominant mode of the hydrological system on the ice sheet scale is, however, ill constrained. A third contribution of this thesis is, using the theory of R-channels to implement a simple numerical model of subglacial water flow, to show the sensitivity of subglacial channels to transient processes and that this limits their possible extent. This insight adds to a cross-disciplinary discussion between the different sub-fields of theoretical, field and paleo-glaciology regarding the characteristics of ice sheet subglacial hydrological systems. In the study, we conclude by emphasizing areas of importance where the sub-fields have yet to unify: the spatial extent of channelized subglacial drainage, to what degree specific processes are connected to geomorphic activity and the differences in spatial and temporal scales.

    As a whole, the thesis emphasizes the importance of verification of numerical models but also acknowledges the natural limitations of these to represent complex systems. Focusing on keeping numerical ice sheet and glacier models as transparent as possible will benefit end users and facilitate accurate interpretations of the numerical output so it confidently can be used for scientific purposes.

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  • 343.
    Helanow, Christian
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Effects of numerical implementations of the impenetrability condition on non-linear Stokes flow: applications to ice dynamicsManuscript (preprint) (Other academic)
    Abstract [en]

    The basal sliding of glaciers and ice sheets can constitute a large part of the total observed ice velocity, in particular in dynamically active areas. It is therefore important to accurately represent this process in numerical models. The condition that the sliding velocity should be tangential to the bed is realized by imposing an impenetrability condition at the base. We study the, in glaciological literature used, numerical implementations of the impenetrability condition for non-linear Stokes flow with Navier's slip on the boundary. Using the finite element method, we enforce impenetrability by: a local rotation of the coordinate system (strong method), a Lagrange multiplier method enforcing zero average flow across each facet (weak method) and an approximative method that uses the pressure variable as a Lagrange multiplier for both incompressibility and impenetrability. An analysis of the latter shows that it relaxes the incompressibility constraint, but enforces impenetrability approximately if the pressure is close to the normal component of the stress at the bed. Comparing the methods numerically using a method of manufactured solutions unexpectedly leads to similar convergence results. However, we find that, for more realistic cases, in areas of high sliding or varying topography the velocity field simulated by the approximative method differs from that of the other methods by approx. 1% (two dimensional flow) and  > 5% when compared to the strong method (three-dimensional flow). In this study the strong method, which is the most commonly used in numerical ice sheet models, emerges as the preferred method due to its stable properties (compared to the weak method in three dimensions) and ability to well enforce the impenetrability condition.

  • 344.
    Helanow, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ahlkrona, Josefin
    Galerkin Least-Squares Stabilization in Ice Sheet Modeling - Accuracy, Robustness, and Comparison to other TechniquesManuscript (preprint) (Other academic)
    Abstract [en]

    We investigate the accuracy and robustness of one of the most common methods used in glaciology for the discretization of the p-Stokes equations: equal order finite elements with Galerkin Least-Squares (GLS) stabilization. Furthermore we compare the results to other stabilized methods. We find that the vertical velocity component is more sensitive to the choice of GLS stabilization parameter than horizontal velocity. Additionally, the accuracy of the vertical velocity component is especially important since errors in this component can cause ice surface instabilities and propagate into future ice volume predictions. If the element cell size is set to the minimum edge length and the stabilization parameter is allowed to vary non-linearly with viscosity, the GLS stabilization parameter found in literature is a good choice on simple domains. However, near ice margins the standard parameter choice may result in significant oscillations in the vertical component of the surface velocity. For these cases, other stabilization techniques, such as the interior penalty method, result in better accuracy and are less sensitive to the choice of the stabilization parameter. During this work we also discovered that the manufactured solutions often used to evaluate errors in glaciology are not reliable due to high artificial surface forces at singularities. We perform our numerical experiments in both FEniCS and Elmer/Ice.

  • 345.
    Helanow, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ahlkrona, Josefin
    Stabilized equal low-order finite elements in ice sheet modeling - accuracy and robustness2018In: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499, Vol. 22, no 4, p. 951-974Article in journal (Refereed)
    Abstract [en]

    We investigate the accuracy and robustness of one of the most common methods used in glaciology for finite element discretization of the oe-Stokes equations: linear equal order finite elements with Galerkin least-squares (GLS) stabilization on anisotropic meshes. Furthermore, we compare the results to other stabilized methods. We find that the vertical velocity component is more sensitive to the choice of GLS stabilization parameter than horizontal velocity. Additionally, the accuracy of the vertical velocity component is especially important since errors in this component can cause ice surface instabilities and propagate into future ice volume predictions. If the element cell size is set to the minimum edge length and the stabilization parameter is allowed to vary non-linearly with viscosity, the GLS stabilization parameter found in literature is a good choice on simple domains. However, near ice margins the standard parameter choice may result in significant oscillations in the vertical component of the surface velocity. For these reasons, other stabilization techniques, in particular the interior penalty method, result in better accuracy and are less sensitive to the choice of stabilization parameter. During this work, we also discovered that the manufactured solutions often used to evaluate errors in glaciology are not reliable due to high artificial surface forces at singularities. We perform our numerical experiments in both FEniCS and Elmer/Ice.

  • 346.
    Helanow, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Meierbachtol, Toby
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Steady-state water pressures in subglacial conduits: corrections to a model and recommendations for its use2015In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 61, no 225, p. 202-204Article in journal (Other academic)
  • 347.
    Hellblom, Ellen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Risk för TBE (Tick BorneEncephalitis) – för vem, var, när, hur och varför?: En metodkritisk studie2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There are a variety of ways to understand the meaning of the phenomenon 'risk for TBE' and how it can be presented. This paper problematises the existing understanding and interpretation of the phenomena by health services and research. The method and empirical knowledge of the present understanding is analysed methodically by a synergy between two interpretation methods. The aim is to show that another methodological approach is needed to achieve further development of the understanding of the subject. Grounded theory is used to reach conclusions about what knowledge could be presented as relevant empirical material for further studies. The empirical material, in turn, generates the theory that risk for TBE covers more than incidence and that the current way of looking at risk of TBE has its shortcomings.

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  • 348. Hellqvist, Magnus
    et al.
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Norström, Elin
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Geological Survey, Sweden.
    Almgren, Elisabeth
    Johansson, Jenny N.
    Traustadóttir, Ragnheiður
    Environment and climate change during the late Holocene in Hjaltadalur, Skagafjörður, northern Iceland2020In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 102, no 1, p. 68-82Article in journal (Refereed)
    Abstract [en]

    We present an overview of the local environmental development of the valley of Hjaltadalur, situated in Skagafjorour, northern Iceland. The aim of this study is to increase the knowledge about the valley region before and during human settlement in the ninth century. Four mires were investigated after which the Viovik peat bog was selected as the main site for evaluating changes in climate and landscape. The master core from Viovik (V-325) was dated and studied further through sediment analysis, loss-on-ignition (LOI), and pollen analysis. According to the age-depth model, based on three radiocarbon dates and analysis of two tephra layers, the 325 cm long Viovik core comprises approximately 5500 years. In the pollen percentage record, there is a decrease in birch (Betula) and an increase in grass (Poaceae) in the central part of the core, between Hekla 3 horizon at c. 2800 BP and the next dated level at c. 2000 BP. This change corresponds well with previously outlined environmental fluctuations, showing a transition from warm and dry climate to cool and humid climate at this time. Human activity is mainly reflected by a distinct peak in Lactucae pollen in the uppermost part of the core. This change in vegetation corresponds with earlier studies, showing that the vegetation changed dramatically after the colonization of Iceland in the ninth century (during Landnam period, 870-930 AD). The present study shows that a decline in birch started well before human settlement, although the subsequent Viking Age and later settlements continued the deforestation trend.

  • 349.
    Helmens, Karin F.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Katrantsiotis, Christos
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Salonen, J. Sakari
    Shala, Shyhrete
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bos, Johanna A. A.
    Engels, Stefan
    Kuosmanen, Niina
    Luoto, Tomi P.
    Väliranta, Minna
    Luoto, Miska
    Ojala, Antti
    Risberg, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Weckström, Jan
    Warm summers and rich biotic communities during N-Hemisphere deglaciation2018In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 167, p. 61-73Article in journal (Refereed)
    Abstract [en]

    Detailed studies on fossil remains of plants or animals in glacial lake sediments are rare. As a result, environmental conditions right at the moment of deglaciation of the large N-Hemisphere ice-sheets remain largely unknown. Here we study three deglacial phases of the Fennoscandian Ice Sheet as a unique, repeated element in a long sediment record preserved at Soldl in northern Finland. We summarize extensive multi-proxy data (diatoms, phytoliths, chironomids, pollen, spores, non-pollen palynomorphs, macrofossils, lithology, loss-on-ignition, C/N) obtained on glacial lake sediments dated to the early Holocene (ca. 10 kyr BP), early MIS 3 (ca. 50 kyr BP) and early MIS 5a (ca. 80 kyr BP). In contrast to the common view of an unproductive ice-marginal environment, our study reconstructs rich ecosystems both in the glacial lake and along the shores with forest on recently deglaciated land. Higher than present-day summer temperatures are reconstructed based on a large variety of aquatic taxa. Rich biota developed due to the insolation-induced postglacial warming and high nutrient levels, the latter resulting from erosion of fresh bedrock and sediment, leaching of surface soils, decay of plant material under shallow water conditions, and sudden decreases in lake volume. Aquatic communities responded quickly to deglaciation and warm summers and reflect boreal conditions, in contrast to the terrestrial ecosystem which responded with some delay probably due to time required for slow soil formation processes. Birch forest is reconstructed upon deglaciation of the large LGM ice-sheet and shrub tundra following the probably faster melting smaller MIS 4 and MIS 5b ice-sheets. Our study shows that glacial lake sediments can provide valuable palaeo-environmental data, that aquatic biota and terrestrial vegetation rapidly accommodated to new environmental conditions during deglaciation, and that glacial lake ecosystems, and the carbon stored in their sediments, should be included in earth system modeling.

  • 350.
    Helmens, Karin F.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Salonen, J. Sakari
    Plikk, Anna
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Engels, Stefan
    Valiranta, Minna
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brendryen, Jo
    Renssen, Hans
    Major cooling intersecting peak Eemian Interglacial warmth in northern Europe2015In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 122, p. 293-299Article in journal (Refereed)
    Abstract [en]

    The degree of climate instability on the continent during the warmer-than-present Eemian Interglacial (around ca. 123 kyr ago) remains unsolved. Recently published high-resolution proxy data from the North Atlantic Ocean suggest that the Eemian was punctuated by abrupt events with reductions in North Atlantic Deep Water formation accompanied by sea-surface temperature cooling. Here we present multiproxy data at an unprecedented resolution that reveals a major cooling event intersecting peak Eemian warmth on the North European continent. Two independent temperature reconstructions based on terrestrial plants and chironomids indicate a summer cooling of the order of 2-4 degrees C. The cooling event started abruptly, had a step-wise recovery, and lasted 500-1000 yr. Our results demonstrate that the common view of relatively stable interglacial climate conditions on the continent should be revised, and that perturbations in the North Atlantic oceanic circulation under warmer-than-present interglacial conditions may also lead to abrupt and dramatic changes on the adjacent continent.

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