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  • 251. Flink, Anne E.
    et al.
    Hill, Peter
    Noormets, Riko
    Kirchner, Nina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Holocene glacial evolution of Mohnbukta in eastern Spitsbergen2018Ingår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 47, nr 2, s. 390-409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam-bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Konigsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well-preserved geometric networks of ridges, interpreted as crevasse-squeeze ridges inshore of the moraines. The arrangement of crevasse-squeeze ridges suggests that both landform sets were produced during surge-type advances. The terminus position of the 1901-1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display C-14 ages between 5700-7700cal. a BP derived from benthic foraminifera, from a clast-rich mud unit. This unit represents pre-surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15-01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge-type advance occurred in Mohnbukta in the early Holocene, prior to 7700cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

  • 252.
    Flintberg, Therese
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Vad är naturen värd vid exploatering av naturresurser?: En kvalitaitv studie över tillämpningen av kompensationsåtgärder vid två svenska infrastrukturprojekt.2016Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Syftet med studien är att undersöka hur kompensationsåtgärder tillämpas vid två olika infrastrukturprojekt i Sverige. Genom en kvalitativ innehållsanalys av material och dokumentation kring fallen Botniabanan och Förbifart Stockholm har frågor om problem/svårigheter som bedöms förekomma i kompensationsprojekten, hur naturen värdesätts och om kompensationsåtgärder legitimerar exploatering besvarats. Resultatet av studien visar att det finns svårigheter i att utvärdera behovet av kompensationsåtgärder på grund av osäkerheter kring projektens miljöeffekter vilket försvårar valet av lämpliga kompensationer. Infrastrukturprojektens komplexitet, med avseende på de olika naturvärden som påverkas under bygg- och driftskedet komplicerar tillämpningen av kompensationsåtgärder. Miljökonsekvensbeskrivningarnas brist på saklighet, tydlighet och konsekvens ger inte en objektiv bild av behovet av kompensation. Det finns en tydlig risk för underskattning av infrastrukturprojektens påverkan på naturvärdena i skyddade naturområden. Det antropocentriska perspektivet är den centrala utgångspunkten för tillämpningen av kompensationsåtgärder. Kompensationsprincipen legitimerar exploatörers möjlighet till att använda sig av skyddad mark i naturreservat och/eller Natura 2000-områden. 

  • 253.
    Flodin, Charlotte
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Equity in rural water resource development and management: A case study of Kilombero Valley, Tanzania, and the investments delivered by a participatory and demand-driven NGO2015Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The demand-driven and participatory approach to water resource development and management in Tanzania has been both praised and criticized; some see progress where others see increased inequalities. This study focuses on one progressive, demand-driven NGO which has a participatory approach to water resource development and management. This NGO, MSABI, is active in Kilombero Valley in southern Tanzania, and can be considered successful as it manages to keep 91 % of its water points functional, whilst the national average for pump functionality is just above 50 %.

    To study the performance of MSABI from a user perspective, it was decided that two sites in Kilombero Valley should be investigated in terms of users’ views on water access and quality. The identification of sites is based on population density and landcover change, so that the issues of scale and urban bias, as well as changes in the landscape affecting hydrological processes, are accounted for. In total, 29 interviews were conducted (October to November 2014), 15 at the Ifakara study site, the more densely populated location, and 14 at the Mchombe Ward study site. The interviews were semi-structured, using a participatory approach, focusing on users’ perspectives on water sources and the access to and quality of those water sources in dry and rainy seasons. The information gathered was used to construct definitions for water access and quality. These definitions, as well as the two locations and categorization of participants according to socio-economic status, were then used to sort and analyse the collected material.

    The results show that MSABI does not manage to make water accessible in an equitable way because of its demand-driven and participatory approach to water resource development and management. However, MSABI offers the only improved water source at the Mchombe Ward study site, except for one improved open well. MSABI manages to counter urban-bias better than any of the other water resource development and management facilitators encountered at the two study sites. The seasons influence water access, especially at the more peripheral locations, where improved water sources are less common and, as open water sources, are more prone to drought and contamination. When participants in Ifakara seasonally migrate for farming, during 4-5 months per year, the majority’s access to improved water sources is lost. At the distant seasonal fields, open water sources are more common and few report that they treat the unsafe water. The migration to peripheral farmlands coincides with the rainy season, causing open water sources to have their lowest water quality when seasonal migrants utilize them. This underlines the importance of securing safe water supply for people at remote locations, and the important role MSABI plays as water resource developer at those locations.

    In conclusion, if the current demand-driven and participatory approach to water resource development and management is to be retained, regardless of the heavy criticism it has received with regards to equity, this study suggests that the practices of MSABI should be spread further based on MSABI’s ability to increase safe water access at remote locations. Another recommendation is to further look into the effects of seasonal migration on access to safe water. The effect seasonal migration has on water access in Kilombero could exist in other areas in Tanzania or in other countries. The aspect of seasonal migration might show that water access statistics are misleading, as the seasonal water consumption in remote locations risks being omitted in official statistics. 

  • 254. Floriancic, Marius G.
    et al.
    Fischer, Benjamin M. C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Molnar, Peter
    Kirchner, James W.
    van Meerveld, Ilja H. J.
    Spatial variability in specific discharge and streamwater chemistry during low flows: Results from snapshot sampling campaigns in eleven Swiss catchments2019Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 33, nr 22, s. 2847-2866Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Catchments consist of distinct landforms that affect the storage and release of subsurface water. Certain landforms may be the main contributors to streamflow during extended dry periods, and these may vary for different catchments in a given region. We present a unique dataset from snapshot field campaigns during low-flow conditions in 11 catchments across Switzerland to illustrate this. The catchments differed in size (10 to 110 km(2)), varied from predominantly agricultural lowlands to Alpine areas, and covered a range of physical characteristics. During each snapshot campaign, we jointly measured streamflow and collected water samples for the analysis of major ions and stable water isotopes. For every sampling location (basin), we determined several landscape characteristics from national geo-datasets, including drainage area, elevation, slope, flowpath length, dominant land use, and geological and geomorphological characteristics, such as the lithology and fraction of quaternary deposits. The results demonstrate very large spatial variability in specific low-flow discharge and water chemistry: Neighboring sampling locations could differ significantly in their specific discharge, isotopic composition, and ion concentrations, indicating that different sources contribute to streamflow during extended dry periods. However, none of the landscape characteristics that we analysed could explain the spatial variability in specific discharge or streamwater chemistry in multiple catchments. This suggests that local features determine the spatial differences in discharge and water chemistry during low-flow conditions and that this variability cannot be assessed a priori from available geodata and statistical relations to landscape characteristics. The results furthermore suggest that measurements at the catchment outlet during low-flow conditions do not reflect the heterogeneity of the different source areas in the catchment that contribute to streamflow.

  • 255.
    Fogelström, Elsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Guasconi, Daniela
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Dahlgren, Johan P.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Flowering status and individual condition affects phenology in a perennial herbManuskript (preprint) (Övrigt vetenskapligt)
  • 256.
    Forselius, Ellen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Spatial patterns of pollution associated with creosote treated poles in Mälardalen2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Creosote is a product name given to a mixture of several hundred compounds, which is often used to protect wooden poles from rot and insect damage, however it has also been linked to causing cancer in humans. Alternative materials for power poles include concrete, steel, composite and non-treated wooden poles. This report looks at Mälarenergi Elnät ABs 17,000 creosote coated poles and their patterns of pollution. GIS analyses in ArcGIS were used to evaluate which creosote poles are most critical to replace by implementing a system of "penalty points" based on the spatial distribution of the poles. 15 of the creosote poles were selected for a field study to investigate how much creosote is leaked to the ground.1,000 of the power poles were assigned penalty points of 10 or higher which could be a starting point in pole replacement, although the penalty points system could be used in many different ways for this purpose. Of the 15 power poles investigated during the field work, 5 showed higher leakage than recommended by Naturvårdsverkets guidelines for sensitive ground use. These 15 poles only make up 0,1% of Mälarenergi Elnät ABs total creosote coated poles, but the results are considered alarming enough to at least merit further studies of the creosote leakage.

  • 257.
    Frampton, Andrew
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Impact of degrading permafrost on subsurface solute transport pathways and travel times2015Ingår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 51, nr 9, s. 7680-7701Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Subsurface solute transport under surface warming and degrading permafrost conditions is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in the subsurface water and inert solute pathways and travel times are analyzed for different modeled geological configurations. For all simulated cases, the minimum and mean travel times increase nonlinearly with warming irrespective of geological configuration and heterogeneity structure. The timing of the start of increase in travel time depends on heterogeneity structure, combined with the rate of permafrost degradation that also depends on material thermal and hydrogeological properties. The travel time changes depend on combined warming effects of: i) increase in pathway length due to deepening of the active layer, ii) reduced transport velocities due to a shift from horizontal saturated groundwater flow near the surface to vertical water percolation deeper into the subsurface, and iii) pathway length increase and temporary immobilization caused by cryosuction-induced seasonal freeze cycles.

  • 258.
    Frampton, Andrew
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Hyman, J. D.
    Zou, Liangchao
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Royal Institute of Technology (KTH), Sweden.
    Advective Transport in Discrete Fracture Networks With Connected and Disconnected Textures Representing Internal Aperture Variability2019Ingår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 55, nr 7, s. 5487-5501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flow and transport in three-dimensional discrete fracture networks with internal variability in aperture and permeability are investigated using a numerical model. The analysis is conducted for three different texture types representing internal variability considering various correlation lengths and for an increase in domain size corresponding to an increase in network complexity. Internal variability in discrete fracture networks generally increases median travel times and delays arrival of bulk mass transport when compared against reference cases without texture, corresponding to smooth fractures. In particular, internal variability textures with weak connectivity increase travel times nonlinearly with domain size increase, further delaying bulk mass arrival. Textures with strong connectivity can however decrease median travel times, accelerating bulk mass arrival, but only for limited ranges of correlation length and domain size. As domain size increases, travel times of textures with strong connectivity converge toward travel times obtained for classical multivariant Gaussian textures. Thus, accounting for internal fracture variability is potentially significant for improving conservative estimates of bulk mass arrival, flow channeling, and advective and reactive transport in large-scale discrete fracture networks. Further, early mass arrival can arrive significantly earlier for textures with strong connectivity and classical Gaussian textures corresponding to intermediate connectivity but are only slightly affected by textures with weak connectivity. Thus, accounting for internal variability in fractures is also important for accurate estimates of early solute mass arrival. The overall impact on predictive transport modeling will depend on the extent of, or lack of, internal fracture connectivity structure in real-world fractured rocks. Plain Language Summary This study investigates transport of waterborne substances in subsurface fractured bedrock, a topic which is of relevance to applications such as subsurface disposal of spent nuclear fuel, storage of carbon dioxide, and disposal of other hazardous material. A physically based numerical model for simulating water flow in the fractured bedrock system is used. Many model-based studies assume fractures to be smooth planes, which are an acknowledged simplification; however, real-world fractures are known to have rough surface asperities. In our study, we account for fracture roughness by assuming textures with different connectivity structure and investigate how this impacts waterborne transport in bedrock. We demonstrate that this type of fracture roughness can control important features of flow and waterborne mass transport. Specifically, most of the mass will generally arrive later than expected when compared to a smooth fracture plane assumption. However, we also observe that a small percentage of mass can, under certain circumstances, arrive earlier than what would be expected if smooth fracture planes are assumed. This means that the assumption of smooth fracture planes should generally be considered a conservative simplifying assumption in the context of subsurface storage, but it is less likely to be accurate when considering early mass arrival.

  • 259. Fritz, M.
    et al.
    Deshpande, B. N.
    Bouchard, F.
    Högström, E.
    Malenfant-Lepage, J.
    Morgenstern, A.
    Nieuwendam, A.
    Oliva, M.
    Paquette, M.
    Rudy, A. C. A.
    Siewert, Matthias B.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Sjöberg, Ylva
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Weege, S.
    Brief Communication: Future avenues for permafrost science from the perspective of early career researchers2015Ingår i: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 9, nr 4, s. 1715-1720Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accelerating climate change and increased economic and environmental interests in permafrost-affected regions have resulted in an acute need for more directed permafrost research. In June 2014, 88 early career researchers convened to identify future priorities for permafrost research. This multidisciplinary forum concluded that five research topics deserve greatest attention: permafrost landscape dynamics, permafrost thermal modeling, integration of traditional knowledge, spatial distribution of ground ice, and engineering issues. These topics underline the need for integrated research across a spectrum of permafrost-related domains and constitute a contribution to the Third International Conference on Arctic Research Planning (ICARP III).

  • 260.
    Fritzon, Ruben
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Goodfellow, Bradley
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Skelton, Alasdair
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Stroeven, Arjen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Estholm, Madelene
    Caffee, Marc
    Evaluating geochemical evidence of earthquake periodicity, Sparta Fault, Southern GreeceManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Determining prehistoric earthquake periodicity and magnitudes is important for risk assessments in seismically active areas. We evaluate a geochemical method, which has previously been used to identify prehistoric slips on normal fault scarps through an analysis of variations in the concentration of rare earth elements and Y (REE-Y) along vertical transects. Our study object is the Sparta Fault, a normal fault in southern Greece, developed in limestone and previously documented, and dated using 36Cl, to have been last active 464 BC. From geochemical analyses of 39 fault rock samples, we conclude that REE-Y concentrations correlate strongly with the abundance of quartz and possibly other heterogeneities in the fault scarp. Because the sampled fault rock is a protocataclasite, formed at depth, variations in the abundance of quartz are not associated with prehistoric movements along the fault. We therefore conclude that geochemical evidence does not provide a reliable paleoseismic proxy for fault movement. We also present data indicating a co-variation between quartz and 36Cl concentrations, which we suggest requires a re-examination of this widely used application of the cosmogenic nuclide surface exposure dating method.

  • 261. Frolova, Natalia L.
    et al.
    Belyakova, Pelagiya A.
    Grigoriev, Vadim Yu.
    Sazonov, Alexey A.
    Zotov, Leonid V.
    Jarsjö, Jerker
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Runoff fluctuations in the Selenga River Basin2017Ingår i: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 17, nr 7, s. 1965-1976Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Selenga River has historically provided 50% of the total freshwater water input to the Lake Baikal, transporting substances and pollutants that can considerably impact the unique lake ecosystem. In the context of on-going regional to global change, we here aim at identifying and understanding mechanisms behind spatial and temporal variability and trends in the flow of the Selenga River and its tributaries, based on hydrological and meteorological station data (since the 1930s), remote sensing, and statistical analyses. Results show that the flow of the Selenga River exhibits cycles with phases of high flows lasting 12 to 17 years and phases of low flows that historically lasted for about 7 years. However, despite an asynchronous behavior between right-bank tributaries and left-bank tributaries, the flow of the Selenga River near its delta at Lake Baikal has now been low (30% below the 1934-1975 average) for as long as 20 years, due to reduced input from precipitation, particularly during the summer season. Observed decreases in annual maximum hourly flows and decreases in annual minimum 30-day flows are consistent with increasing activation of the groundwater system due to thawing permafrost, and higher winter temperatures that support increased winter flows by preventing rivers to freeze from top to bottom. These recent and relatively large changes have implications for regional water planning and management, including the planned large-scale hydropower expansion in the upper part of the Selenga River Basin.

  • 262.
    Fröcklin, Sara
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Jiddawi, Narriman S.
    de la Torre-Castro, Maricela
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Small-scale innovations in coastal communities: shell-handicraft as a way to empower women and decrease poverty2018Ingår i: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 23, nr 2, artikel-id 34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We analyzed the potential of small-scale innovations, such as shell-handicraft, as a way to foster transformation toward sustainability, decrease poverty, and increase women's empowerment in Zanzibar, Tanzania. The shell-handicraft project was founded by USAID in 2006 and was introduced as an alternative livelihood to low-paid seaweed farming and invertebrate harvesting activities. The main objective, however, was to not only alleviate poverty and empower women, but also to improve management of coastal resources, and allegedly by doing so, break poverty traps. To analyze the potential benefits of this enterprise, and more specifically whether or not women involved in this project have been empowered, a framework was used that comprises three inter-related dimensions; agency, access to resources, and outcome. Agency includes the process of decision making, negotiation, etc., in which choices are made and put into effect. Access to resources (financial, physical, human, and social) is the medium through which agency is exercised, and outcome can be defined as the result of agency. Simply put, resources and agency make up people's potential for living the lives they want. Semistructured interviews were administered to a group of women (n = 36) involved in shell-handicraft and a group of women not involved in shell-handicraft (n = 36) in five villages located in central/south Zanzibar. The results show that over time, the women engaged in shell-handicraft have improved their access to a range of resources, mainly physical (house, cell phone, freezer, and electricity), human (knowledge in marketing, leadership, and entrepreneurship), and social (organization). This further resulted in reported improved self-confidence and decision-making authority within the household. Regarding financial resources, both savings and income improved for the targeted group, but more research is advised. Positively, the environmental impacts of the activity are seemingly low. Old shells are collected for handicraft and a number of no-take zones, as part of the project, have been established to preserve marine resources, which allowed for women's participation in coastal management. The project has also empowered women and challenged stereotypes, aspects critical for progressive and inclusive management. Although all in all, the women interviewed were satisfied and had increased their standard of living, the discussion problematizes this innovation by addressing scaling up possibilities, market constraints, and the kick-off process having external top-down elements. Even though the recipients of the benefits from the project have been few, this case has valuable elements to learn from and can provide inspiration to drive coastal systems into more sustainable paths.

  • 263.
    Frögren, Kristin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Miljöproblem i Sverige: Definition och vanligt förekommande termer2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det saknas i dagsläget en definition av begreppet miljöproblem. Subjektiva definitioner av begreppet skulle kunna leda till missförstånd mellan olika aktörer, kontraproduktivitet eller felriktade insatser för att lösa dessa problem. Därför är syftet med detta examensarbete att utforma en definition för begreppet miljöproblem. Arbetet är baserat på en litteraturstudie som utfördes med kvantitativa metoder, där en sammanställning av relevanta termer från relevant litteratur genomfördes. Enligt resultaten är denna definition: ”Något som orsakar föroreningar eller orsakar förlust av biologisk mångfald, produktionsförmåga eller funktioner.” Definitionen är tillräckligt övergripande, men även tillräckligt specifik för att anses användbar i både vardagligt tal samt vid tillämpning av miljöarbete, forskning och miljöpolitik. Det behövs vidare forskning i ämnet, då denna i dagsläget är ytterst sparsam. Definitionen som utformats här kommer inte att bestå för evigt, utan kommer att fortsätta utvecklas och bearbetas, där ny kunskap, kontexter, nya miljömål etcetera kommer att spela en viktig roll.

  • 264. Fu, Ping
    et al.
    Stroeven, Arjen P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Harbor, Jonathan M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Purdue University, USA.
    Heyman, Jakob
    Hättestrand, Clas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Caffee, Marc W.
    Ice cap erosion patterns from bedrock Be-10 and Al-26, southeastern Tibetan Plateau2019Ingår i: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 44, nr 4, s. 918-932Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas. Combining in situ Be-10 and Al-26 analysis of bedrock, boulder, and river sand samples, geomorphological mapping, and field investigations, we examine glacial erosion patterns of former ice caps in the Shaluli Shan of the southeastern Tibetan Plateau. The general landform pattern shows a zonal pattern of landscape modification produced by ice caps of up to 4000 km(2) during pre-LGM (Last Glacial Maximum) glaciations, while the dating results and landforms on the plateau surface imply that the LGM ice cap further modified the scoured terrain into different zones. Modeled glacial erosion depth of 0-0.38 m per 100 ka bedrock sample located close to the western margin of the LGM ice cap, indicates limited erosion prior to LGM and Late Glacial moraine deposition. A strong erosion zone exists proximal to the LGM ice cap marginal zone, indicated by modeled glacial erosion depth >2.23 m per 100 ka from bedrock samples. Modeled glacial erosion depths of 0-1.77 m per 100 ka from samples collected along the edge of a central upland, confirm the presence of a zone of intermediate erosion in-between the central upland and the strong erosion zone. Significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate restricted glacial erosion during the last glaciation. Our study, for the first time, shows clear evidence for preservation of glacial landforms formed during previous glaciations under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the Haizishan ice cap during the LGM.

  • 265.
    Fuchs, Matthias
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Hugelius, Gustaf
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Low below-ground organic carbon storage in a subarctic Alpine permafrost environment2015Ingår i: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 9, nr 2, s. 427-438Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates the soil organic carbon (SOC) storage in Tarfala Valley, northern Sweden. Field inventories, upscaled based on land cover, show that this alpine permafrost environment does not store large amounts of SOC, with an estimate mean of 0.9 +/- 0.2 kg C m(-2) for the upper meter of soil. This is 1 to 2 orders of magnitude lower than what has been reported for lowland permafrost terrain. The SOC storage varies for different land cover classes and ranges from 0.05 kg C m(-2) for stone-dominated to 8.4 kg C m(-2) for grass-dominated areas. No signs of organic matter burial through cryoturbation or slope processes were found, and radiocarbon-dated SOC is generally of recent origin (< 2000 cal yr BP). An inventory of permafrost distribution in Tarfala Valley, based on the bottom temperature of snow measurements and a logistic regression model, showed that at an altitude where permafrost is probable the SOC storage is very low. In the high-altitude permafrost zones (above 1500 m), soils store only ca. 0.1 kg C m(-2). Under future climate warming, an upward shift of vegetation zones may lead to a net ecosystem C uptake from increased biomass and soil development. As a consequence, alpine permafrost environments could act as a net carbon sink in the future, as there is no loss of older or deeper SOC from thawing permafrost.

  • 266. Gaetani, Marco
    et al.
    Messori, Gabriele
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU).
    Zhang, Qiong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Flamant, Cyrille
    Pausata, Francesco S. R.
    Stockholms universitet, Naturvetenskapliga fakulteten, Meteorologiska institutionen (MISU). University of Quebec in Montreal, Canada.
    Understanding the Mechanisms behind the Northward Extension of the West African Monsoon during the Mid-Holocene2017Ingår i: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, nr 19, s. 7621-7642Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding the West African monsoon (WAM) dynamics in the mid-Holocene (MH) is a crucial issue in climate modeling, because numerical models typically fail to reproduce the extensive precipitation suggested by proxy evidence. This discrepancy may be largely due to the assumption of both unrealistic land surface cover and atmospheric aerosol concentration. In this study, the MH environment is simulated in numerical experiments by imposing extensive vegetation over the Sahara and the consequent reduction in airborne dust concentration. A dramatic increase in precipitation is simulated across the whole of West Africa, up to the Mediterranean coast. This precipitation response is in better agreement with proxy data, in comparison with the case in which only changes in orbital forcing are considered. Results show a substantial modification of the monsoonal circulation, characterized by an intensification of large-scale deep convection through the entire Sahara, and a weakening and northward shift (similar to 6.5 degrees) of the African easterly jet. The greening of the Sahara also leads to a substantial reduction in the African easterly wave activity and associated precipitation. The reorganization of the regional atmospheric circulation is driven by the vegetation effect on radiative forcing and associated heat fluxes, with the reduction in dust concentration to enhance this response. The results for the WAM in the MH present important implications for understanding future climate scenarios in the region and in teleconnected areas, in the context of projected wetter conditions in West Africa.

  • 267. Gallego-Sala, Angela
    et al.
    Charman, Dan J.
    Brewer, Simon
    Page, Susan E.
    Prentice, I. Colin
    Friedlingstein, Pierre
    Moreton, Steve
    Amesbury, Matthew J.
    Beilman, David W.
    Bjorck, Svante
    Blyakharchuk, Tatiana
    Bochicchio, Christopher
    Booth, Robert K.
    Bunbury, Joan
    Camill, Philip
    Carless, Donna
    Chimner, Rodney A.
    Clifford, Michael
    Cressey, Elizabeth
    Courtney-Mustaphi, Colin
    De Vleeschouwer, Francois
    de Jong, Rixt
    Fialkiewicz-Koziel, Barbara
    Finkelstein, Sarah A.
    Garneau, Michelle
    Githumbi, Esther
    Hribjlan, John
    Holmquist, James
    Hughes, Paul D. M.
    Jones, Chris
    Jones, Miriam C.
    Karofeld, Edgar
    Klein, Eric S.
    Kokfelt, Ulla
    Korhola, Atte
    Lacourse, Terri
    Le Roux, Gael
    Lamentowicz, Mariusz
    Large, David
    Lavoie, Martin
    Loisel, Julie
    Mackay, Helen
    MacDonald, Glen M.
    Makila, Markku
    Magnan, Gabriel
    Marchant, Robert
    Marcisz, Katarzyna
    Martinez Cortizas, Antonio
    Massa, Charly
    Mathijssen, Paul
    Mauquoy, Dmitri
    Mighall, Timothy
    Mitchell, Fraser J. G.
    Moss, Patrick
    Nichols, Jonathan
    Oksanen, Pirita O.
    Orme, Lisa
    Packalen, Maara S.
    Robinson, Stephen
    Roland, Thomas P.
    Sanderson, Nicole K.
    Sannel, A. Britta K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Silva-Sanchez, Noemi
    Steinberg, Natascha
    Swindles, Graeme T.
    Turner, T. Edward
    Uglow, Joanna
    Valiranta, Minna
    van Bellen, Simon
    van der Linden, Marjolein
    van Geel, Bas
    Wang, Guoping
    Yu, Zicheng
    Zaragoza-Castells, Joana
    Zhao, Yan
    Latitudinal limits to the predicted increase of the peatland carbon sink with warming2018Ingår i: Nature Climate Change, ISSN 1758-678X, E-ISSN 1758-6798, Vol. 8, nr 10, s. 907-+Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around AD 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.

  • 268. Gardeström, Johanna
    et al.
    Ermold, Matti
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Swedish University of Agricultural Sciences, Sweden.
    Goedkoop, Willem
    McKie, Brendan G.
    Disturbance history influences stressor impacts: effects of a fungicide and nutrients on microbial diversity and litter decomposition2016Ingår i: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, Vol. 61, nr 12, s. 2171-2184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Streams draining agricultural catchments are severely degraded by multiple stressors, including nutrient enrichment and pesticides. The understanding of how such stressors interact to alter ecosystem structure and function, and how responses of biota reflect their longer-term disturbance history, remains limited. We conducted a multifactorial stream microcosm experiment to investigate how elevated nutrients and a fungicide (azoxystrobin) interact to affect multiple variables associated with leaf decomposition: the biomass, sporulation rate and diversity of aquatic hyphomycete decomposers, litter decomposition rates and detritivore growth. We further manipulated decomposer species composition by using three distinct fungal assemblages drawn from streams with contrasting histories of agricultural disturbance: a forest stream, a mixed land-use stream subject to nutrient enrichment but little pesticide use, and an agricultural stream subjected to both intensive nutrient and pesticide use. We also varied the presence of the detritivorous isopod Asellus aquaticus. The fungicide azoxystrobin reduced both biomass and diversity of aquatic hyphomycetes and growth of A.aquaticus, and had negative knock-on effects on leaf decomposition and fungal sporulation. These impacts further varied with nutrient concentration. Impacts of the fungicide differed markedly among the three fungal assemblages. The agricultural assemblages were dominated by tolerant species and showed some capacity for maintaining processes under pesticide exposure, whereas diversity and functioning were strongly suppressed in the forest stream assemblage, which was dominated by stress-intolerant species. Pesticides, in interaction with other agricultural stressors, can impact microbial diversity and key ecosystem processes underlying the delivery of ecosystem services from streams. The extent of such impacts vary according to the longer-term disturbance history of the biota, and might be most acute when agricultural activity expands into previously uncultivated catchments, as is currently occurring in many regions of the world.

  • 269.
    Gartz, Mira
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Plantdiversitet på svenska slåtterängar: En GIS-analys med kulturella perspektiv2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    En hög plantdiversitet är beroende av ett landskap som erbjuder tillräckligt stora habitat, funktionell konnektivitet och heterogenitet. Habitatförlust och förändrad markanvändning utgör det största hotet mot biodiversitet idag. Det svenska landskapet har inte bara förändrats dramatiskt de senaste 60 åren, det innehåller också några av Europas sista fragment av de mycket värdefulla slåtterängarna. Många av de svenska slåtterängarna är upptagna i Natura 2000-områden. Trots detta finns inga systematiska bevarandestrategier för dessa slåtterängar och arbetet hänger mestadels på volontärer. Den här studien ämnar bidra till en ökad förståelse för hur omgivande landskap påverkar plantdiversiteten på svenska slåtterängar. GIS-analyser av lokala landskap som omger 21 svenska slåtterängar har utförts. Nedslag vid två tidpunkter har gjorts; år 1950 och 2015. Genom digitalisering av kartor från 1950-talet har arean av marktyper kunnat beräknas och sedan jämföras med dagens markanvändning och artdata i samma områden. Resultaten visar att den totala skogsarealen har ökat med 12% sedan 1950-talet och det finns negativa samband mellan både den historiska och den nutida skogsarealen och artrikedomen på ängarna. Arean av åkermark har minskat med 19% i de undersökta områdena, men inga samband med artrikedomen kunde finnas. Däremot visade det sig att den före detta åkermark som fanns på 1950-talet påverkar dagens artrikedomen negativ, både som ensam oberoende variabel och tillsammans med öppen mark. Öppen mark har minskat med mellan 17% och 24%, men inga samband mellan denna landskapskategori och plantdiversiteten fanns. De sammanställda resultaten indikerar att den historiska markanvändningen på lokal skala har större påverkan på dagens plantdiversitet än den nutida markanvändningen. Detta bör tas i beaktande vid utformande av bevarandestrategier och vid fysisk planering.

  • 270.
    Ghajarnia, Navid
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Arasteh, P. Daneshkar
    Liaghat, M.
    Araghinejad, S.
    Error Analysis on PERSIANN Precipitation Estimations: Case Study of Urmia Lake Basin, Iran2018Ingår i: Journal of hydrologic engineering, ISSN 1084-0699, E-ISSN 1943-5584, Vol. 23, nr 6, artikel-id 05018006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In-depth evaluation and analysis of the error properties associated with satellite-based precipitation estimation algorithms can play an important role in the future development and improvements of these products. This study evaluates the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) daily data set from 2000 to 2011 in 69 pixels over a semiarid basin in northwest Iran and compares it with the data set of the existing rain-gauge network. Different analytical approaches and measures are used to examine PERSIANN performance seasonally and categorically. The residuals are also decomposed into true positive (hit), false negative (miss), and false alarm (FA) estimate biases in addition to systematic and random error components. The results show seasonal variability of PERSIANN precision in rainfall detection with substantial errors during winter and summer that are associated with high rates of FA ratio (more than 60%). The value of miss and FA biases (124 and -77,000mm, respectively, within the total data set) are considerably larger than hit and total bias (27 and 74,000mm, respectively) because these components contribute conversely and compensate each other by their opposite signs. Moreover, PERSIANN detects heavy rainfalls well with a probability of detection (POD) over 80%, but with serious biases. Generally, although the detection ability of PERSIANN improves as the rate of rainfall increases, its systematic error in simulation of the rainfall process also increases (from 5% systematic error to 90% in heavier rainfalls), leading to a low level of accuracy in the estimation of precipitation rate.

  • 271. Giesler, Reiner
    et al.
    Lyon, Steve W.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Mörth, Carl-Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Karlsson, Jan
    Karlsson, E. M.
    Jantze, Elin J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Humborg, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Catchment-scale dissolved carbon concentrations and exportestimates across six subarctic streams in northern Sweden2014Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, s. 525-537Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climatic change is currently enhancing permafrostthawing and the flow of water through the landscape in subarcticand arctic catchments, with major consequences forthe carbon export to aquatic ecosystems. We studied streamwater carbon export in several tundra-dominated catchmentsin northern Sweden. There were clear seasonal differencesin both dissolved organic carbon (DOC) and dissolved inorganiccarbon (DIC) concentrations. The highest DOC concentrationsoccurred during the spring freshet while the highestDIC concentrations were always observed during winterbaseflow conditions for the six catchments considered in thisstudy. Long-term trends for the period 1982 to 2010 for oneof the streams showed that DIC concentrations has increasedby 9% during the 28 yr of measurement while no clear trendwas found for DOC. Similar increasing trends were alsofound for conductivity, Ca and Mg. When trends were discretizedinto individual months, we found a significant linearincrease in DIC concentrations with time for September,November and December. In these subarctic catchments, theannual mass of C exported as DIC was in the same orderof magnitude as DOC; the average proportion of DIC to thetotal dissolved C exported was 61% for the six streams. Furthermore,there was a direct relationship between total runoffand annual dissolved carbon fluxes for these six catchments.These relationships were more prevalent for annual DIC exportsthan annual DOC exports in this region. Our results alsohighlight that both DOC and DIC can be important in highlatitudeecosystems. This is particularly relevant in environmentswhere thawing permafrost and changes to subsurfaceice due to global warming can influence stream water fluxesof C. The large proportion of stream water DIC flux also hasimplications on regional C budgets and needs to be consideredin order to understand climate-induced feedback mechanismsacross the landscape.

  • 272.
    Girons Lopez, Marc
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Modelling Climatic and Hydrological Variability in Lake Babati, Northern Tanzania2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    A good understanding of the local and regional water cycle and how it is modified by landscape changes may help policymakers take the pertinent decisions in order to avoid adverse effects of future hydro–climatic changes. This knowledge is of particular interest in the most vulnerable areas of the world such as the African continent. In this context the aim of this project is to model hydrological responses to possible changes in climatic conditions in Lake Babati, northern Tanzania. For this reason a water balance model specially designed to simulate lake level changes was adapted to Lake Babati and calibrated with the available local meteorological and hydrological data record covering the last decades. The necessary ambient condition changes to produce a dry–out and an overflow of the lake were investigated and the response of the system to future IPCC climate change projections was studied. The results show that for instance a temperature change of less than 3ºC or a precipitation change of around 100 mm/year could eventually bring the lake from a dry–out situation to an overflow situation. Furthermore, the IPCC derived scenarios show a clear tendency of the lake to increase its volume and reach the overflow level in a relatively short time.

  • 273. Gisnås, Kjersti
    et al.
    Etzelmuller, Bernd
    Lussana, Cristian
    Hjort, Jan
    Sannel, A. Britta K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Isaksen, Ketil
    Westermann, Sebastian
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Christiansen, Hanne H.
    Frampton, Andrew
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Åkerman, Jonas
    Permafrost Map for Norway, Sweden and Finland2017Ingår i: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 28, nr 2, s. 359-378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A research-based understanding of permafrost distribution at a sufficient spatial resolution is important to meet the demands of science, education and society. We present a new permafrost map for Norway, Sweden and Finland that provides a more detailed and updated description of permafrost distribution in this area than previously available. We implemented the CryoGRID1 model at 1km(2) resolution, forced by a new operationally gridded data-set of daily air temperature and snow cover for Finland, Norway and Sweden. Hundred model realisations were run for each grid cell, based on statistical snow distributions, allowing for the representation of sub-grid variability of ground temperature. The new map indicates a total permafrost area (excluding palsas) of 23 400km(2) in equilibrium with the average 1981-2010 climate, corresponding to 2.2 per cent of the total land area. About 56 per cent of the area is in Norway, 35 per cent in Sweden and 9 per cent in Finland. The model results are thoroughly evaluated, both quantitatively and qualitatively, as a collaboration project including permafrost experts in the three countries. Observed ground temperatures from 25 boreholes are within +/- 2 degrees C of the average modelled grid cell ground temperature, and all are within the range of the modelled ground temperature for the corresponding grid cell. Qualitative model evaluation by field investigators within the three countries shows that the map reproduces the observed lower altitudinal limits of mountain permafrost and the distribution of lowland permafrost.

  • 274. Glasser, Neil F.
    et al.
    Jansson, Krister N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Duller, Geoffrey A. T.
    Singarayer, Joy
    Holloway, Max
    Harrison, Stephan
    Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 21064Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredon basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface hosing to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate.

  • 275. Glimskär, Anders
    et al.
    Skånes, Helle
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Land Type Categories as a Complement to Land Use and Land Cover Attributes in Landscape Mapping and Monitoring2015Ingår i: Land Use and Land Cover Semantics: Principles, Best Practices, and Prospects / [ed] Ola Ahlqvist, Dalia Varanka, Steffen Fritz, and Krzysztof Janowicz, Boca Raton: CRC Press, 2015, s. 171-190Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The purpose of land cover and land use descriptions varies, and this influences how these concepts are perceived in different contexts. The increasing need for spatial data for multipurpose monitoring and modeling also increases the demands for compatibility, repeatability, detail, and well-documented criteria. We suggest that threshold values along a continuous scale can be used to create nominal classes for a common conceptual framework. However, the exact values of these thresholds need to be based on well-defined functional and systematic criteria. Ecological and environmental gradients are often mosaic and complex, and several types of land use may coexist at the same site. In reality, land use can be seen as a “shifting cloud” of activities varying in both time and space. We advocate the use of strict definitions of land cover as physical structures and land use as human activities, which raises the need for a complementary concept, which we call “land type,” with stable threshold values based on mutually exclusive functional criteria. Such functional criteria often put clear limits to what spatial resolution is appropriate, since the suitability for a certain purpose (e.g., agriculture or forestry) is determined by the user of the land, rather than by the independent observer. Our example of land type categories comprises a two-level hierarchical classification with seven main types and altogether 28 subtypes. As an example, we discuss the overlapping Swedish definitions of forest and arable land. The criteria that define our main land types are less dependent on how the area is managed at a specific moment in time, and they are therefore less sensitive to short-term variation. The land types define the limits for what land cover and land use can be expected at a certain site, given, for example, ground conditions, water, or artificial structures. Since such land types need to incorporate functional and qualitative understanding and interpretation, human visual interpretation is needed, whereas automated remote sensing methods are suitable mainly for the structural aspects of land cover.

  • 276. Godtman Kling, Kristin
    et al.
    Dahlberg, Annika
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Wall-Reinius, Sandra
    Negotiating Improved Multifunctional Landscape Use: Trails as Facilitators for Collaboration Among Stakeholders2019Ingår i: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, nr 13, artikel-id 3511Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Trails are significant features in landscapes, and many ancient pathways have developed into routes of great importance for recreation and tourism in contemporary societies. Nevertheless, international research on recreational trails has hitherto mainly focused on managerial and environmental aspects of trails and less on trails from a social science perspective, such as conflict management. This study explores the role of recreational trails as a potential tool for managing conflicts in a multifunctional landscape. The findings originate from a case study of the southern Jamtland mountain region in Sweden, an area where land-use conflicts exist and where tourism is a major concern. The study examines the recreational trail as an applied example where actors in the mountain landscape negotiate and collaborate. through the recreational trail, dialogue and discussions are made possible among stakeholders. Findings show that trails can function as facilitators for communication and can thus enhance the possibilities of building trust and promoting collaboration between actors. This research contributes to the existing literature on handling multiple land-use interests and adds to previous knowledge by taking on a rather new approach, where the recreational trail becomes a facilitator for communication.

  • 277.
    Goldenberg, Romain
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Kalantari, Zahra
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Cvetkovic, Vladimir
    Mörtberg, Ulla
    Deal, Brian
    Destouni, Georgia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Distinction, quantification and mapping of potential and realized supply-demand of flow-dependent ecosystem services2017Ingår i: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 593, s. 599-609Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study addresses and conceptualizes the possible dependence of ecosystem services on prevailing air and/or water flow processes and conditions, and particularly on the trajectories and associated spatial reach of these flows in carrying services from supply to demand areas in the landscape. The present conceptualization considers and accounts for such flow-dependence in terms of potential and actually realized service supply and demand, which may generally differ and must therefore be distinguished due to and accounting for the prevailing conditions of service carrier flows. We here concretize and quantify such flow-dependence for a specific landscape case (the Stockholm region, Sweden) and for two examples of regulating ecosystem services: local climate regulation and storm water regulation. For these service and landscape examples, we identify, quantify and map key areas of potential and realized service supply and demand, based for the former (potential) on prevailing relatively static types of landscape conditions (such as land-cover/use, soil type and demographics), and for the latter (realized) on relevant carrier air and water flows. These first-order quantification examples constitute first steps towards further development of generally needed such flow-dependence assessments for various types of ecosystem services in different landscapes over the world.

  • 278. Goni, Maria Fernanda Sanchez
    et al.
    Desprat, Stephanie
    Daniau, Anne-Laure
    Bassinot, Frank C.
    Polanco-Martinez, Josue M.
    Harrison, Sandy P.
    Allen, Judy R. M.
    Anderson, R. Scott
    Behling, Hermann
    Bonnefille, Raymonde
    Burjachs, Francesc
    Carrion, Jose S.
    Cheddadi, Rachid
    Clark, James S.
    Combourieu-Nebout, Nathalie
    Mustaphi, Colin. J. Courtney
    Debusk, Georg H.
    Dupont, Lydie M.
    Finch, Jemma M.
    Fletcher, William J.
    Giardini, Marco
    Gonzalez, Catalina
    Gosling, William D.
    Grigg, Laurie D.
    Grimm, Eric C.
    Hayashi, Ryoma
    Helmens, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Heusser, Linda E.
    Hill, Trevor
    Hope, Geoffrey
    Huntley, Brian
    Igarashi, Yaeko
    Irino, Tomohisa
    Jacobs, Bonnie
    Jimenez-Moreno, Gonzalo
    Kawai, Sayuri
    Kershaw, A. Peter
    Kumon, Fujio
    Lawson, Ian T.
    Ledru, Marie-Pierre
    Lezine, Anne-Marie
    Liew, Ping Mei
    Magri, Donatella
    Marchant, Robert
    Margari, Vasiliki
    Mayle, Francis E.
    McKenzie, G. Merna
    Moss, Patrick
    Mueller, Stefanie
    Mueller, Ulrich C.
    Naughton, Filipa
    Newnham, Rewi M.
    Oba, Tadamichi
    Perez-Obiol, Ramon
    Pini, Roberta
    Ravazzi, Cesare
    Roucoux, Katy H.
    Rucina, Stephen M.
    Scott, Louis
    Takahara, Hikaru
    Tzedakis, Polichronis C.
    Urrego, Dunia H.
    van Geel, Bas
    Valencia, B. Guido
    Vandergoes, Marcus J.
    Vincens, Annie
    Whitlock, Cathy L.
    Willard, Debra A.
    Yamamoto, Masanobu
    The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period2017Ingår i: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 9, nr 2, s. 679-695Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D-O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73-15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (C-14, U-234/Th-230, optically stimulated luminescence (OSL), Ar-40/Ar-39-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft Access (TM) at https://doi. org/10.1594/PANGAEA. 870867.

  • 279. Govaert, Sanne
    et al.
    Meeussen, Camille
    Vanneste, Thomas
    Bollmann, Kurt
    Brunet, Jörg
    Cousins, Sara A. O.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Diekmann, Martin
    Graae, Bente J.
    Hedwall, Per-Ola
    Heinken, Thilo
    Iacopetti, Giovanni
    Lenoir, Jonathan
    Lindmo, Sigrid
    Orczewska, Anna
    Perring, Michael P.
    Ponette, Quentin
    Plue, Jan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Selvi, Federico
    Spicher, Fabien
    Tolosano, Matteo
    Vermeir, Pieter
    Zellweger, Florian
    Verheyen, Kris
    Vangansbeke, Pieter
    De Frenne, Pieter
    Edge influence on understorey plant communities depends on forest management2020Ingår i: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Questions: Does the influence of forest edges on plant species richness and composition depend on forest management? Do forest specialists and generalists show contrasting patterns?

    Location: Mesic, deciduous forests across Europe.

    Methods: Vegetation surveys were performed in forests with three management types (unthinned, thinned 5-10 years ago and recently thinned) along a macroclimatic gradient from Italy to Norway. In each of 45 forests, we established five vegetation plots along a south-facing edge-to-interior gradient (n = 225). Forest specialist, generalist and total species richness, as well as evenness and proportion of specialists, were tested as a function of the management type and distance to the edge while accounting for several environmental variables (e.g. landscape composition and soil characteristics). Magnitude and distance of edge influence were estimated for species richness per management type.

    Results: Greatest total species richness was found in thinned forests. Edge influence on generalist plant species richness was contingent on the management type, with the smallest decrease in species richness from the edge-to-interior in unthinned forests. In addition, generalist richness increased with the proportion of forests in the surrounding landscape and decreased in forests dominated by tree species that cast more shade. Forest specialist species richness, however, was not affected by management type or distance to the edge, and only increased with pH and increasing proportion of forests in the landscape.

    Conclusions: Forest thinning affects the plant community composition along edge-to-interior transects of European forests, with richness of forest specialists and generalists responding differently. Therefore, future studies should take the forest management into account when interpreting edge-to-interior because both modify the microclimate, soil processes and deposition of polluting aerosols. This interaction is key to predict the effects of global change on forest plants in landscapes characterized by the mosaic of forest patches and agricultural land that is typical for Europe.

  • 280.
    Gowan, Evan J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. The Australian National University, Australia.
    Tregoning, Paul
    Purcell, Anthony
    Lea, James
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. University of Liverpool, UK.
    Fransner, Oscar J.
    Noormets, Riko
    Dowdeswell, J. A.
    ICESHEET 1.0: a program to produce paleo-ice sheet reconstructions with minimal assumptions2016Ingår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, nr 5, s. 1673-1682Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We describe a program that produces paleo-ice sheet reconstructions using an assumption of steady-state, perfectly plastic ice flow behaviour. It incorporates three input parameters: ice margin, basal shear stress and basal topography. Though it is unlikely that paleo-ice sheets were ever in complete steady-state conditions, this method can produce an ice sheet without relying on complicated and unconstrained parameters such as climate and ice dynamics. This makes it advantageous to use in glacial-isostatic adjustment ice sheet modelling, which are often used as input parameters in global climate modelling simulations. We test this program by applying it to the modern Greenland Ice Sheet and Last Glacial Maximum Barents Sea Ice Sheet and demonstrate the optimal parameters that balance computational time and accuracy.

  • 281.
    Gowan, Evan J.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. The Australian National University, Australia.
    Tregoning, Paul
    Purcell, Anthony
    Montillet, Jean-Philippe
    McClusky, Simon
    A model of the western Laurentide Ice Sheet, using observations of glacial isostatic adjustment2016Ingår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 139, s. 1-16Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    We present the results of a new numerical model of the late glacial western Laurentide Ice Sheet, constrained by observations of glacial isostatic adjustment (GIA), including relative sea level indicators, uplift rates from permanent GPS stations, contemporary differential lake level change, and postglacial tilt of glacial lake level indicators. The later two datasets have been underutilized in previous GIA based ice sheet reconstructions. The ice sheet model, called NAICE, is constructed using simple ice physics on the basis of changing margin location and basal shear stress conditions in order to produce ice volumes required to match GIA. The model matches the majority of the observations, while maintaining a relatively realistic ice sheet geometry. Our model has a peak volume at 18,000 yr BP, with a dome located just east of Great Slave Lake with peak thickness of 4000 m, and surface elevation of 3500 m. The modelled ice volume loss between 16,000 and 14,000 yr BP amounts to about 7.5 m of sea level equivalent, which is consistent with the hypothesis that a large portion of Meltwater Pulse 1A was sourced from this part of the ice sheet. The southern part of the ice sheet was thin and had a low elevation profile. This model provides an accurate representation of ice thickness and paleo-topography, and can be used to assess present day uplift and infer past climate.

  • 282.
    Greenwood, Sarah L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Clason, Caroline C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Helanow, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Margold, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Durham University, UK.
    Theoretical, contemporary observational and palaeo-perspectives on ice sheet hydrology: Processes and products2016Ingår i: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 155, s. 1-27Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Meltwater drainage through ice sheets has recently been a key focus of glaciological research due to its influence on the dynamics of ice sheets in a warming climate. However, the processes, topologies and products of ice sheet hydrology are some of the least understood components of both past and modem ice sheets. This is to some extent a result of a disconnect between the fields of theoretical, contemporary observational and palaeo-glaciology that each approach ice sheet hydrology from a different perspective and with different research objectives. With an increasing realisation of the potential of using the past to inform on the future of contemporary ice sheets, bridging the gaps in the understanding of ice sheet hydrology has become paramount. Here, we review the current state of knowledge about ice sheet hydrology from the perspectives of theoretical, observational and palaeo-glaciology. We then explore and discuss some of the key questions in understanding and interpretation between these research fields, including: 1) disagreement between the palaeo-record, glaciological theory and contemporary observations in the operational extent of channelised subglacial drainage and the topology of drainage systems; 2) uncertainty over the magnitude and frequency of drainage events associated with geomorphic activity; and 3) contrasts in scale between the three fields of research, both in a spatial and temporal context The main concluding points are that modem observations, modelling experiments and inferences from the palaeo-record indicate that drainage topologies may comprise a multiplicity of forms in an amalgam of drainage modes occurring in different contexts and at different scales. Drainage under high pressure appears to dominate at ice sheet scale and might in some cases be considered efficient; the sustainability of a particular drainage mode is governed primarily by the stability of discharge. To gain better understanding of meltwater drainage under thick ice, determining what drainage topologies are reached under high pressure conditions is of primary importance. Our review attests that the interconnectivity between research sub-disciplines in progressing the field is essential, both in interpreting the palaeo-record and in developing physical understanding of glacial hydrological processes and systems.

  • 283.
    Greenwood, Sarah L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Clason, Caroline C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Mikko, Henrik
    Nyberg, Johan
    Peterson, Gustaf
    Smith, Colby A.
    Integrated use of LiDAR and multibeam bathymetry reveals onset of ice streaming in the northern Bothnian Sea2015Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 137, nr 4, s. 284-292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Geomorphological mapping from the new LiDAR (Light Detection and Ranging)-derived digital elevation model for Sweden and a high-resolution multibeam bathymetry data-set for the Gulf of Bothnia reveals a continuous system of glacial landforms crossing the transition between the modern terrestrial and marine environments. A palaeo-ice stream in the northern Bothnian Sea is reconstructed, with an onset tributary over the present-day angstrom ngermanland-Vasterbotten coastline. Systematic contrasts in landform morphology and lineation length indicate that this ice stream comprised a relatively narrow (approximate to 40km) corridor of fast flow, flowing first SW then S, and likely fed by converging flow around the upper Bothnian Sea. The geometry and landform associations of this system imply that ice, at the time period represented here, did not flow across the Gulf of Bothnia: SSE-ward ice flow indicators on the northern Swedish coast do not correspond directly with landform assemblages of the large SE-oriented Finnish deglacial lobes. Instead, we suggest they may contribute to a late-stage fast-flow event to the S and SW. Multibeam bathymetry data offer entirely new access into the rich, landform-scale geomorphological record on the seafloor of the Gulf of Bothnia. The combination of offshore multibeam with the new terrestrial LiDAR data provides unprecedented insight into and renewed understanding of the glacial dynamics of the Bothnian Sea sector of the Fennoscandian Ice Sheet, hitherto interpreted over large areas of unmapped ice sheet bed.

  • 284.
    Greenwood, Sarah L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Clason, Caroline C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. University of Plymouth, UK.
    Nyberg, Johan
    Jakobsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Holmlund, Per
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    The Bothnian Sea ice stream: early Holocene retreat dynamics of the south-central Fennoscandian Ice Sheet2017Ingår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 46, nr 2, s. 346-362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Gulf of Bothnia hosted a variety of palaeo-glaciodynamic environments throughout the growth and decay of the last Fennoscandian Ice Sheet, from the main ice-sheet divide to a major corridor of marine-and lacus-trine-based deglaciation. Ice streaming through the Bothnian and Baltic basins has been widely assumed, and the damming and drainage of the huge proglacial Baltic Ice Lake has been implicated in major regional and hemispheric climate changes. However, the dynamics of palaeo-ice flow and retreat in this large marine sector have until now been inferred only indirectly, from terrestrial, peripheral evidence. Recent acquisition of high-resolution multibeam bathymetry opens these basins up, for the first time, to direct investigation of their glacial footprint and palaeo-ice sheet behaviour. Here we report on a rich glacial landform record: in particular, a palaeo-ice stream pathway, abundant traces of high subglacial meltwater volumes, and widespread basal crevasse squeeze ridges. The Bothnian Sea ice stream is a narrow flow corridor that was directed southward through the basin to a terminal zone in the south-central Bothnian Sea. It was activated after initial margin retreat across the Aland sill and into the Bothnian basin, and the exclusive association of the ice-stream pathway with crevasse squeeze ridges leads us to interpret a short-lived stream event, under high extension, followed by rapid crevasse-triggered break-up. We link this event with a c. 150-year ice-rafted debris signal in peripheral varved records, at c. 10.67 cal. ka BP. Furthermore, the extensive glacifluvial system throughout the Bothnian Sea calls for considerable input of surface meltwater. We interpret strongly atmospherically driven retreat of this marine-based ice-sheet sector.

  • 285. Greilich, S.
    et al.
    Gribenski, Natacha
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Mittelstrass, D.
    Dornich, K.
    Huot, S.
    Preusser, Frank
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Single-grain dose-distribution measurements by optically stimulated luminescence using an integrated EMCCD-based system2015Ingår i: Quaternary Geochronology, ISSN 1871-1014, E-ISSN 1878-0350, Vol. 29, s. 70-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the feasibility of assessing single-grain dose-distributions by using an EMCCD-based imaging system with complementary analysis software. Automated image-processing was successfully applied to compensate sample motion and for grain identification. Following a dose recovery test, 74% of the grains were recognized successfully, and 44% exhibited a suitable OSL dose response behavior to interpolate an equivalent dose value, and a central dose recovery ratio of 1.038 was obtained.

  • 286. Grenier, Christophe
    et al.
    Anbergen, Hauke
    Bense, Victor
    Chanzy, Quentin
    Coon, Ethan
    Collier, Nathaniel
    Costard, Francois
    Ferry, Michel
    Frampton, Andrew
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Frederick, Jennifer
    Goncalves, Julio
    Holmen, Johann
    Jost, Anne
    Kokh, Samuel
    Kurylyk, Barret
    McKenzie, Jeffrey
    Molson, John
    Mouche, Emmanuel
    Orgogozo, Laurent
    Pannetier, Romain
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Riviere, Agnes
    Roux, Nicolas
    Ruehaak, Wolfram
    Scheidegger, Johanna
    Selroos, Jan-Olof
    Therrien, Rene
    Vidstrand, Patrik
    Voss, Clifford
    Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases2018Ingår i: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 114, s. 196-218Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In high-elevation, boreal and arctic regions, hydrological processes and associated water bodies can be strongly influenced by the distribution of permafrost. Recent field and modeling studies indicate that a fully-coupled multidimensional thermo-hydraulic approach is required to accurately model the evolution of these permafrost-impacted landscapes and groundwater systems. However, the relatively new and complex numerical codes being developed for coupled non-linear freeze-thaw systems require verification. This issue is addressed by means of an intercomparison of thirteen numerical codes for two-dimensional test cases with several performance metrics (PMs). These codes comprise a wide range of numerical approaches, spatial and temporal discretization strategies, and computational efficiencies. Results suggest that the codes provide robust results for the test cases considered and that minor discrepancies are explained by computational precision. However, larger discrepancies are observed for some PMs resulting from differences in the governing equations, discretization issues, or in the freezing curve used by some codes.

  • 287.
    Gribenski, Natacha
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Comparison of dating methods for paleoglacial reconstruction in Central Asia2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Reconstruction of former Central Asian glaciers extents can provide valuable information about past atmospheric circulation variations. These extents, often marked by terminal moraines, need to be chronologically constrained. Cosmogenic nuclide exposure (CNE) dating is widely used to directly date moraines. In addition, there is increasing interest on using optically stimulated luminescence (OSL) techniques for dating glacial landforms. This thesis focuses on the methodological aspects of directly dating glacial landforms to perform paleoglacial reconstructions in Central Asia, with an emphasis on OSL dating.

    For OSL dating of sediments from glacial settings, it is important to measure the luminescence signal at the single grain scale, because the sediments are likely affected by partial bleaching due to short light exposure during glacial or glaciofluvial transport. The use of an Electron Multiplying Charges Coupled Device (EMCCD)-based imaging system for single grain OSL measurements would offer larger flexibility in light stimulation and sediment type, compared to the current Single Grain Risø reader. An automated image processing procedure has been developed to compensate for sample carrier displacement over repeated measurements and for attributing pixels to each grain for signal integration when using this imaging system. However, significant cross talk contamination, demonstrated by laboratory and simulation experiments, prohibits accurate single grain luminescence measurements. Preliminary experiments using a basic image processing algorithm show good potential for software correction solutions.

    Paleoglacial reconstructions conducted in the Altai Mountains, Central Asia, using both CNE and OSL dating demonstrate that luminescence measurements of glaciofluvial sediments performed at the multi-grain scale result in large age overestimates, and that single grain measurements allow for more accurate dating of glacial landforms. However, uncertainties remain that are related to the model used for extracting equivalent doses for well-bleached grains and to fading corrections when using feldspar minerals. The timing of glaciation can be inferred from scattered CNE moraine boulder ages if most of the ages are concentrated within a few thousand years, with only few ages clearly older or younger. Overall, combining CNE and OSL techniques for dating a glacial landform is a powerful approach for producing robust glacial chronologies, despite uncertainties inherent to each technique.

    Paleoglacial reconstructions from the Altai Mountains indicate Marine Isotope Stage (MIS) 2 and MIS 4/late MIS 5 local Last Glacial Maximums. In Central Asia, in addition to a regional MIS 2 glaciation, previous studies indicate a period of major glacial advances during MIS 3 that is out of phase with global ice volume records. However, most MIS 3 glacial chronologies from Central Asia are based on too few or too heavily scattered CNE data sets, or on OSL or Electron Spin Resonance (ESR) ages for which partial bleaching has not been properly investigated. Hence, at this stage, chronological evidence is insufficient to demonstrate a regional MIS 3 glaciation in Central Asia.

    Surge-related glacial features identified in the Russian Altai also highlight the importance of conducting detailed geomorphology and sedimentology studies to understand former ice dynamics, which is essential for inferring appropriate paleoclimate information from paleoglacial reconstructions.

  • 288.
    Gribenski, Natacha
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Jansson, Krister N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Lukas, Sven
    Stroeven, Arjen P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Harbor, Jonathan M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Purdue University, USA.
    Blomdin, Robin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Ivanov, Mikhail N.
    Heyman, Jakob
    Petrakov, Dmitry A.
    Rudoy, Alexei
    Clifton, Tom
    Lifton, Nathaniel A.
    Caffee, Marc W.
    Complex patterns of glacier advances during the late glacial in the Chagan Uzun Valley, Russian Altai2016Ingår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 149, s. 288-305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Southern part of the Russian Altai Mountains is recognized for its evidence for catastrophic glacial lake outbursts. However, little is known about the late Pleistocene paleoglacial history, despite the interest in such reconstructions for constraining paleoclimate. In this study, we present a detailed paleoglaciological reconstruction of the Chagan Uzun Valley, in the Russian Altai Mountains, combining for the first time detailed geomorphological mapping, sedimentological logging, and in situ cosmogenic 10Be and 26Al surface exposure dating of glacially-transported boulders. The Chagan Uzun Valley exhibits the most impressive glacial landforms of this sector of the Altai, with extensive lobate moraine belts deposited in the intramontane Chuja Basin, reflecting a series of pronounced former glacial advances. Observations of “hillside-scale” folding and extensive faulting of pre-existing soft sediments within the outer moraine belts, together with the geomorphology, strongly indicate that these moraine belts were formed during surge-like events. Identification of surge-related features is essential for paleoclimate inference because these features correspond to a glacier system that is not in equilibrium with the contemporary climate, but instead largely influenced by various internal and external factors. Therefore, no strict relationship can be established between climatic variables and the pronounced distal glacial extent observed in the Chagan Uzun Valley/Chuja basin. In contrast, the inner (up-valley) glacial landforms of the Chagan Uzun valley were likely deposited during retreat of temperate valley glaciers, close to equilibrium with climate, and so most probably triggered by a general warming. Cosmogenic ages associated with the outermost, innermost, and intermediate stages all indicate deposition times clustered around 19 ka. However, the actual deposition time of the outermost moraine may slightly predate the 10Be ages due to shielding caused by subsequent lake water coverage. This chronology indicates a Marine Isotope Stage (MIS) 2 last maximum extent of the Chagan Uzun Glacier, and an onset of the deglaciation around 19 ka. This is consistent with other regional paleoclimate proxy records and with the Northern Hemisphere glaciation chronology. Finally, this study also highlights the highly dynamic environment in this area, with complex interactions between glacial events and the formation and drainage of lakes.

  • 289.
    Gribenski, Natacha
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Leibniz Institute for Applied Geophysics, Germany.
    Jansson, Krister N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Preusser, Frank
    Harbor, Jonathan M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Purdue University, USA.
    Stroeven, Arjen P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Trauerstein, Mareike
    Blomdin, Robin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Heyman, Jakob
    Caffee, Marc W.
    Lifton, Nathaniel A.
    Zhang, Wei
    Re-evaluation of MIS 3 glaciation using cosmogenic radionuclide and single grain luminescence ages, Kanas Valley, Chinese Altai2018Ingår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 33, nr 1, s. 55-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Previous investigations observed a period of major glacial advances in Central Asia during marine oxygen isotope stage (MIS) 3 (57-29 ka), out of phase with global ice volume records. We have re-examined the Kanas moraine complex in the Altai Mountains of Central Asia, where an MIS 3 glaciation had been previously inferred. New and consistent cosmogenic exposure and single-grain luminescence ages indicate that the Kanas complex was formed during MIS 2 (29-12 ka), which brings its timing in line with the global ice volume record. We also identified a lateral moraine from a more extensive ice extent that dates to late MIS 5/MIS 4. To place our results in a wider contextual framework, we review the chronologies of another 26 proposed major MIS 3 glacial advances in Central Asia. For most of these sites, we find that the chronological data do not provide an unequivocal case for MIS 3 glaciation.

  • 290.
    Gribenski, Natacha
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Jansson, Krister N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Preusser, Frank
    Harbor, Jonathan M.
    Stroeven, Arjen P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Trauerstien, Mareike
    Blomdin, Robin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Heyman, Jakob
    Caffee, Marc W.
    Lifton, Nathaniel
    Zhang, Wei
    Major glaciation in Central Asia during MIS 3: reality or dating artefact?Manuskript (preprint) (Övrigt vetenskapligt)
    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.

  • 291.
    Gribenski, Natacha
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Lukas, Sven
    Stroeven, Arjen P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Jansson, Krister N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Harbor, Jonathan M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi. Purdue University, USA.
    Blomdin, Robin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    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, 288-3052017Ingår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 168, s. 219-221Artikel i tidskrift (Refereegranskat)
  • 292.
    Gribenski, Natacha
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Preusser, Frank
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Greilich, Steffen
    Huot, Sebastien
    Mittestrass, Dirk
    Investigation of cross talk in single grain luminescence measurements using an EMCCD camera2015Ingår i: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 81, s. 163-170Artikel i tidskrift (Refereegranskat)
    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.

  • 293.
    Groth, Erika
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    En studie av sambandet mellan urbanisering och maximiflödena i Hagbyån i Stockholms län2016Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Befolkningen i Stockholmsregionen har ökat kraftigt under de senaste decennierna och förväntas fortsätta öka i framtiden. Ökad urbanisering medför normalt att andelen hårdgjorda ytor ökar. På hårdgjorda ytor som tak, vägar och parkeringsplatser kan vattnet inte infiltrera marken utan rinner av längs ytan som dagvatten. En ökad andel hårdgjorda ytor antas därför resultera i högre och snabbare avrinning, särskilt vid kraftiga regn, vilket ökar risken för översvämningar. I Stockholms län förväntas den pågående klimatförändringen leda till ökad nederbörd, speciellt på vintern, och dessutom förväntas det bli vanligare med extremt kraftiga skyfall.

    I den här studien undersöker jag kopplingen mellan urbaniseringsgraden, mätt både som befolkningstäthet och som andelen hårdgjorda ytor, och storleken på de årliga maximiflödena i Hagbyån nära Vallentuna från andra hälften av 1900-talet och fram till nutid. Hårdgjorda ytor definieras i denna studie som byggnader, vägar, järnvägar och stigar och beräknas utifrån fastighetskartan som representerar nutid och den ekonomiska kartan som representerar studieperiodens början. Återkomsttiderna för årsmaximivattenflödena beräknas utifrån dagliga värden på vattenföringen vid Skällnora mätstation med frekvensanalys enligt de tre metoderna Weibullmetoden, Gringortenmetoden och Gumbelmetoden.

    Urbaniseringsgraden i studieområdet har som förväntat ökat vilket märks både på att befolkningen i kommunerna och i den största tätorten i studieområdet har ökat och på att andelen hårdgjorda ytor nästan har fördubblats från studieperiodens början till nutid. Trots detta har storleken på årsmaximiflödena minskat. När storleken på 100-årsflödena vid Skällnora mätstation beräknas baserat på årsmaximiflödena från första hälften av studieperioden blir 100-årsflödet 3,9 m3/s men när årsmaximiflödena från andra hälften av studieperioden används blir 100-årsflödet 2,4 m3/s. De största flödena har blivit ovanligare. Detta är tvärtemot det förväntade resultatet som var att årsmaximiflödena skulle öka med ökad andel hårdgjorda ytor.

    Detta resultat beror inte på minskad nederbörd. Den här studien inkluderade inte någon analys av hur evapotranspirationen i området har förändrats över tid. Ett varmare klimat med mindre snö och en förskjutning av nederbörden till vintern skulle kunna vara en bidragande orsak till att årsmaximiflödena har minskat.

  • 294.
    Groß, Elisabeth
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Mård, Johanna
    Kalantari, Zahra
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Bring, Arvid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Links between Nordic and Arctic hydroclimate and vegetation changes: Contribution to possible landscape-scale nature-based solutions2018Ingår i: Land Degradation and Development, ISSN 1085-3278, E-ISSN 1099-145X, Vol. 29, nr 10, s. 3663-3673Artikel i tidskrift (Refereegranskat)
    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.

  • 295.
    Guittard, Alice
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    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, Colombia2016Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    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.

  • 296.
    Gullberg, Rebecka
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Carbon - Past, Present and Future: Effects of 20th century land use on soil organic carbon in Nynäs nature reserve, Sweden2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    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.

  • 297. Gustafsson, Jon Petter
    et al.
    Belyazid, Salim
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    McGivney, Eric
    Löfgren, Stefan
    Aluminium and base cation chemistry in dynamic acidification models - need for a reappraisal?2018Ingår i: soil, ISSN 2199-3971, Vol. 4, nr 4, s. 237-250Artikel i tidskrift (Refereegranskat)
    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.

  • 298.
    Gustav, Alm
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Vegetationsutvecklingen och människans påverkan på vegetationen kring Sojdmyr på Östra Gotland från cal 4000 BP till nutid2018Självständigt arbete på avancerad nivå (masterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    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.

  • 299. 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
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    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 set2019Ingår i: Dendrochronologia, ISSN 1125-7865, E-ISSN 1612-0051, Vol. 57, artikel-id 125624Artikel i tidskrift (Refereegranskat)
    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.

  • 300.
    Gärdsberg, Adam
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Geografiundervisning på högstadiet: Geografilärare med olika ämneskombinationer och deras syn på ämnet samt utformning av undervisning2017Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    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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