Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Geologi) "

Sökning: hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Geologi)

Sortera/gruppera träfflistan
  • Bernhardson, Martin (författare)
  • Aeolian dunes of central Sweden
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • In the Swedish inland there are aeolian deposits present, ranging from scattered single dunes to dune fields of more than 10 km2. These dune fields often pass unnoticed since they presently are covered by vegetation. However, they contain a rich palaeoenvironmental archive. Only a few research papers have been published regarding these aeolian deposits during the last 90 years. The primary scope of this thesis has been to determine why these dunes formed, when they formed, and what they can tell us about the environment during their formation. The results from these investigations are presented in four research papers.The shape and orientation of a dune is determined by the local environment during its formation, such as the abundance of sediment available for entrainment by the wind, groundwater table fluctuations, changes to precipitation and temperature, presence/absence of vegetation, mode of the wind et cetera. By determining the type of dunes it is possible to determine the local environment during their formation. If one also can determine when these dunes formed and stabilised one can determine the palaeoenvironment, and in extension the palaeoclimate, during a specific time period.In this thesis, new findings are presented regarding the geomorphology, geochronology and palaeoenvironment of a number of dunes and dune fields in south and central Sweden, based on state-of-the-art methods, such as LiDAR (light detection and ranging) based remote sensing and optically stimulated luminescence dating. The previous hypotheses concerning the formation of these dunes have also been evaluated.The findings show that the dunes of central Sweden are primarily of a transverse type, i.e. their dune ridges are transverse to the dune forming winds and they were formed in a setting devoid of vegetation and with an abundance of sediment. The primary dune forming winds for these transverse dunes appear to have been north-westerly and westerly winds. The investigated dunes further to the south show signs of having been reworked after their initial formation and are often of a parabolic type, i.e. curved/crescentic in shape with their arms facing upwind. These dunes have been described as strongly linked to the presence of vegetation, and can often be considered secondary dune forms. These more southern dunes appear to also mainly have been formed by north-westerly and westerly winds, although they display a bigger scatter in wind directions than the more northern dunes.The luminescence ages suggest that most of the dunes formed during the early Holocene, and later events of sand drift have been uncommon with only minor impact on the dune morphology. There seems to have been a primary dune stabilisation phase ~10-9 ka, irrespective of the latitude of the dune fields. This means that some dune fields formed close after local deglaciation, while others formed millennia later. This suggests that dune formation and dune stabilisation of central Sweden have been controlled by regional environmental conditions. Extremely low lake levels in southern and south-central Sweden 10.5-9.5 ka BP in conjunction with an unstable climate during early Holocene probably delayed dune stabilisation by vegetation. After the vegetation had stabilised the dunes, they became much more resilient to further fluctuations in the climate.
  • Earon, Robert, et al. (författare)
  • Groundwater Resources Potential in Hard Rock Terrain : A Multivariate Approach
  • 2014
  • Ingår i: Ground Water. - : John Wiley & Sons. - 0017-467X .- 1745-6584.
  • Tidskriftsartikel (refereegranskat)abstract
    • Groundwater resources are limited and difficult to predict in crystalline bedrock due to heterogeneity and anisotropy in rock fracture systems. Municipal-level governments often lack the resources for traditional hydrogeological tests when planning for sustainable use of water resources. A new methodology for assessing groundwater resources potential (GRP) based on geological and topographical factors using principal component analysis (PCA) and analysis of variance (ANOVA) was developed and tested. ANOVA results demonstrated statistically significant differences in classed variable groups as well as in classed GRP scores with regard to hydrogeological indicators, such as specific capacity (SC) and transmissivity. Results of PCA were used to govern the weight of the variables used in the prediction maps. GRP scores were able to identify 79% of wells in a verification dataset, which had SC values less than the total dataset median. GRP values showed statistically significant correlations using both parametric (using transformed datasets) and non-parametric methods. The method shows promise for municipal or regional level planning in crystalline terrains with high levels of heterogeneity and anisotropy as a hydrogeologically and statistically based tool to assist in assessing groundwater resources. The methodology is executed in a geographic information systems environment, and uses often readily available data, such as geological maps, feature maps and topography, and thus does not require expensive and time-consuming aquifer tests.
  • Kirchner, N., et al. (författare)
  • Capabilities and limitations of numerical ice sheet models : a discussion for Earth-scientists and modelers
  • 2011
  • Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 30:25-26, s. 3691-3704
  • Tidskriftsartikel (refereegranskat)abstract
    • The simulation of dynamically coupled ice sheet, ice stream, and ice shelf-systems poses a challenge to most numerical ice sheet models. Here we review present ice sheet model limitations targeting a broader audience within Earth Sciences, also those with no specific background in numerical modeling, in order to facilitate cross-disciplinary communication between especially paleoglaciologists, marine and terrestrial geologists, and numerical modelers. The ‘zero order’(Shallow Ice Approximation, SIA)-,‘higher order’-, and‘full Stokes’ice sheet models are described conceptually and complemented by an outline of their derivations. We demonstrate that higher order models are required to simulate coupled ice sheetice shelf and ice sheet-ice stream systems, in particular if the results are aimed to complement spatial ice flow reconstructions based on higher resolution geological and geophysical data. The zero order SIA model limitations in capturing ice stream behavior are here illustrated by conceptual simulations of a glaciation on Svalbard. The limitations are obvious from the equations comprising a zero order model. However, under certain circumstances, simulation results may falsely give the impression that ice streams indeed are simulated with a zero order SIA model.
  • Margold, Martin, 1981-, et al. (författare)
  • Glacial Lake Vitim, a 3000 km³ outburst flood from Siberia to the Arctic Ocean
  • 2011
  • Ingår i: Quaternary Research. - 0033-5894 .- 1096-0287. ; 76:3, s. 393-396
  • Tidskriftsartikel (refereegranskat)abstract
    • A prominent lake formed when glaciers descending from the Kodar Range blocked the River Vitim in central Transbaikalia, Siberia. Glacial Lake Vitim, evidenced by palaeoshorelines and deltas, covered 23,500 km2 and held a volume of ~3000 km3. We infer that a large canyon in the area of the postulated ice dam served as a spillway during an outburst flood that drained through the rivers Vitim and Lena into the Arctic Ocean. The inferred outburst flood, of a magnitude comparable to the largest known floods on Earth, possibly explains a freshwater spike at ~13 cal ka BP inferred from Arctic Ocean sediments.
  • Margold, Martin, 1981-, et al. (författare)
  • Late-glacial ice dynamics of the Cordilleran Ice Sheet in northern British Columbia and southern Yukon Territory : retreat pattern of the Liard Lobe reconstructed from the glacial landform record
  • Annan publikation (övrigt vetenskapligt)abstract
    • The Liard Lobe formed a part of the northeastern sector of the Cordilleran Ice Sheet and drained ice from accumulation areas in the Selwyn, Pelly, Cassiar and Skeena mountains. This study reconstructs the ice retreat pattern of the Liard Lobe during the last deglaciation from the glacial landform record that is comprised of glacial lineations and landforms of the meltwater system such as eskers, meltwater channels, perched deltas and outwash fans. The spatial distribution of these landforms defines the successive configurations of the ice sheet during the deglaciation. The Liard Lobe retreated to the west and southwest across the Hyland Highland from its local Last Glacial Maximum position in the southeastern Mackenzie Mountains where it coalesced with the Laurentide Ice Sheet. The retreat across the Liard Lowland and a subsequent splitting of the thus far uniform ice surface into several ice lobes is evidenced by large esker complexes that stretch across the Liard Lowland cutting across the contemporary drainage network. Ice margin positions from the late stage of deglaciation are reconstructed locally at the foot of the Cassiar Mountains and farther up-valley in an eastern facing valley of the Cassiar Mountains. The presented landform record indicates that the deglaciation of the Liard Lobe was accomplished mainly by active ice retreat and that ice stagnation did not play a significant role in the deglaciation of this region.
  • Margold, Martin, 1981-, et al. (författare)
  • Late-glacial retreat pattern of the Cordilleran Ice Sheet in central British Columbia reconstructed from glacial meltwater landforms
  • Tidskriftsartikel (refereegranskat)abstract
    • The Cordilleran Ice Sheet (CIS) covered much of the mountainous northwestern part of North America during Pleistocene glaciations. In contrast to other ephemeral Pleistocene ice sheets, the pattern and timing of growth and decay of the CIS are poorly understood. Here, we present a reconstruction of the pattern of late-glacial ice sheet retreat in central British Columbia based on a palaeoglaciological interpretation of ice-marginal meltwater channels, eskers, and deltas mapped from satellite imagery and digital elevation models. A consistent spatial pattern of high-elevation ice-marginal meltwater channels (1600-2400 m a.s.l.) occurs across central British Columbia. They indicate the presence of ice domes over the Skeena Mountains and the central Coast Mountains early during deglaciation. Ice sourced in the Coast Mountains remained dominant over the southern and east-central parts of the Interior Plateau during late-glacial time. Our reconstruction shows a successive westward retreat of the ice margin away from the western foot of the Rocky Mountains, accompanied by the formation and rapid evolution of a glacial lake in the upper Fraser River basin. Final stages of deglaciation were characterized by the frontal retreat of ice lobes through the valleys of the Skeena and Omineca mountains and by the formation of large esker systems in the most prominent topographic lows of the Interior Plateau. We conclude that the CIS underwent a large-scale reconfiguration early during deglaciation and subsequently diminished by thinning and complex frontal retreat towards the Coast Mountains.
  • Routh, Joyanto, 1968-, et al. (författare)
  • Sedimentary geochemical record of humanï¿œinduced environmental changes in the Lake Brunnsviken watershed, Sweden
  • 2004
  • Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 49:5, s. 1560-1569
  • Tidskriftsartikel (refereegranskat)abstract
    • Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These human-induced perturbations within the lakeï¿œs watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller d15Ntotal values, high organic carbon mass accumulation rates, low C:N ratios, and larger d13Corg values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C: S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.
  • Routh, Joyanto, 1968-, et al. (författare)
  • Sedimentary organic matter sources and depositional environment in the Yegua formation (Brazos County, Texas)
  • 1999
  • Ingår i: Organic Geochemistry. - : Elsevier. - 0146-6380 .- 1873-5290. ; 30:11, s. 1437-1453
  • Tidskriftsartikel (refereegranskat)abstract
    • The complex depositional environment of the Eocene Yegua formation (Brazos County, Texas) can be better understood by integrating organic matter (OM) geochemistry with stratigraphy. Yegua sediments represent parasequences separated by exposure surfaces. Organic petrography and geochemistry (biomarkers, C/N ratios, and carbon isotopes) indicate the presence of both terrestrial and marine OM in transgressive sediments. In contrast, regressive sediments contain only terrestrial OM. These differences relate to contrasting OM sources and depositional styles on the shelf. OM in the sediments is immature and the potential for generating hydrocarbons is poor. The study suggests that organic geochemical data can help in distinguishing transgressive and regressive environments in sedimentary formations.
  • Åkesson, Sofia, et al. (författare)
  • Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach
  • 2020
  • Ingår i: Ambio: a Journal of Human Environment. - : Springer. - 0044-7447 .- 1654-7209. ; 50, s. 1074-1088
  • Tidskriftsartikel (refereegranskat)abstract
    • A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater.
  • Bonaglia, Stefano, et al. (författare)
  • The fate of fixed nitrogen in marine sediments with low organic loading : an in situ study
  • 2017
  • Ingår i: Biogeosciences. - : Copernicus Publications. - 1726-4170 .- 1726-4189. ; 14:2, s. 285-300
  • Tidskriftsartikel (refereegranskat)abstract
    • Over the last decades, the impact of human activities on the global nitrogen (N) cycle has drastically increased. Consequently, benthic N cycling has mainly been studied in anthropogenically impacted estuaries and coasts, while in oligotrophic systems its understanding is still scarce. Here we report on benthic solute fluxes and on rates of denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) studied by in situ incubations with benthic chamber landers during two cruises to the Gulf of Bothnia (GOB), a cold, oligotrophic basin located in the northern part of the Baltic Sea. Rates of N burial were also inferred to investigate the fate of fixed N in these sediments. Most of the total dissolved fixed nitrogen (TDN) diffusing to the water column was composed of organic N. Average rates of dinitrogen (N-2) production by denitrification and anammox (range: 53-360 mu mol Nm(-2) day(-1)) were comparable to those from Arctic and subarctic sediments worldwide (range: 34-344 mu mol Nm(-2) day(-1)). Anammox accounted for 18-26% of the total N2 production. Absence of free hydrogen sulfide and low concentrations of dissolved iron in sediment pore water suggested that denitrification and DNRA were driven by organic matter oxidation rather than chemolithotrophy. DNRA was as important as denitrification at a shallow, coastal station situated in the northern Bothnian Bay. At this pristine and fully oxygenated site, ammonium regeneration through DNRA contributed more than one-third to the TDN efflux and accounted, on average, for 45% of total nitrate reduction. At the offshore stations, the proportion of DNRA in relation to denitrification was lower (0-16% of total nitrate reduction). Median value and range of benthic DNRA rates from the GOB were comparable to those from the southern and central eutrophic Baltic Sea and other temperate estuaries and coasts in Europe. Therefore, our results contrast with the view that DNRA is negligible in cold and well-oxygenated sediments with low organic carbon loading. However, the mechanisms behind the variability in DNRA rates between our sites were not resolved. The GOB sediments were a major source (237 kt yr(-1), which corresponds to 184% of the external N load) of fixed N to the water column through recycling mechanisms. To our knowledge, our study is the first to document the simultaneous contribution of denitrification, DNRA, anammox, and TDN recycling combined with in situ measurements.
Skapa referenser, mejla, bekava och länka
Typ av publikation
tidskriftsartikel (3080)
konferensbidrag (617)
doktorsavhandling (278)
bokkapitel (196)
annan publikation (114)
rapport (91)
visa fler...
forskningsöversikt (84)
licentiatavhandling (44)
bok (17)
samlingsverk (redaktörskap) (15)
recension (11)
proceedings (redaktörskap) (7)
visa färre...
Typ av innehåll
refereegranskat (3358)
övrigt vetenskapligt (997)
populärvet., debatt m.m. (197)
Weihed, Pär (138)
SÖderlund, Ulf (128)
Björck, Svante (126)
Ahlberg, Per (116)
Martinsson, Olof (100)
Alexanderson, Helena (99)
visa fler...
Schmitz, Birger (98)
Eriksson, Mats (86)
Vajda, Vivi (85)
Calner, Mikael (81)
Conley, Daniel (77)
Wanhainen, Christina (71)
Koyi, Hemin (70)
Hammarlund, Dan (69)
Muscheler, Raimund (68)
Lindgren, Johan (65)
Möller, Per (64)
Allen, Rodney (63)
Majka, Jaroslaw (60)
Snowball, Ian (60)
Scherstén, Anders (57)
Weihed, Pär, 1959- (57)
Johansson, Leif (50)
Whitehouse, Martin J ... (49)
Troll, Valentin (45)
Lehnert, Oliver (43)
Högdahl, Karin (42)
Stephens, Michael B. (41)
Jonsson, Erik (40)
Ebbestad, Jan Ove R. ... (39)
Bauer, Tobias (39)
Rundgren, Mats (37)
Jakobsson, Martin (37)
Möller, Charlotte (37)
Bengtson, Stefan, 19 ... (37)
Skovsted, Christian, ... (37)
Billström, Kjell (37)
Burchardt, Steffi (36)
Stevens, Thomas, 197 ... (36)
Terfelt, Fredrik (35)
Ernst, Richard E. (35)
Troll, Valentin R. (33)
Wohlfarth, Barbara (32)
Broström, Anna (32)
Conley, Daniel J. (31)
Alwmark, Carl (31)
Whitehouse, Martin (31)
Possnert, G (30)
Harper, David A.T. (30)
Skyttä, Pietari (30)
visa färre...
Lunds universitet (1925)
Uppsala universitet (1235)
Stockholms universitet (604)
Luleå tekniska universitet (580)
Naturhistoriska riksmuseet (338)
Umeå universitet (100)
visa fler...
Kungliga Tekniska Högskolan (58)
Linnéuniversitetet (44)
Linköpings universitet (33)
Södertörns högskola (29)
Göteborgs universitet (23)
Högskolan i Gävle (21)
Högskolan Kristianstad (19)
Naturvårdsverket (17)
Högskolan Dalarna (10)
RISE (9)
Örebro universitet (6)
Högskolan Väst (4)
Sveriges Lantbruksuniversitet (4)
VTI - Statens väg- och transportforskningsinstitut (3)
Mittuniversitetet (2)
Chalmers tekniska högskola (2)
Karolinska Institutet (2)
Jönköping University (1)
Malmö universitet (1)
Högskolan i Halmstad (1)
Högskolan i Borås (1)
Försvarshögskolan (1)
Blekinge Tekniska Högskola (1)
Karlstads universitet (1)
visa färre...
Engelska (4281)
Svenska (249)
Tyska (8)
Danska (4)
Spanska (3)
Ryska (2)
visa fler...
Norska (2)
Annat språk (2)
Franska (1)
Italienska (1)
Estniska (1)
visa färre...
Forskningsämne (UKÄ/SCB)
Naturvetenskap (4554)
Teknik (70)
Humaniora (69)
Samhällsvetenskap (16)
Lantbruksvetenskap (15)
Medicin och hälsovetenskap (6)


pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy