Now showing items 130-149 of 316

    • Ice-sheet-driven methane storage and release in the Arctic 

      Portnov, Aleksei D; Vadakkepuliyambatta, Sunil; Mienert, Jurgen; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-07)
      It is established that late-twentieth and twenty-first century ocean warming has forced dissociation of gas hydrates with concomitant seabed methane release. However, recent dating of methane expulsion sites suggests that gas release has been ongoing over many millennia. Here we synthesize observations of B1,900 fluid escape features—pockmarks and active gas flares—across a previously glaciated ...
    • Ice-stream dynamics of the SW Barents Sea revealed by high-resolution 3D seismic imaging of glacial deposits in the Hoop area 

      Bellwald, Benjamin; Planke, Sverre; Piasecka, Emilia Daria; Matar, M.A.; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-07)
      Recent developments in seismic acquisition systems and seismic data visualization have contributed to improve the imaging of seismic geomorphologies over a broad range of topics. This study focuses on a new high-resolution P-Cable 3D seismic cube located in the Hoop area in the SW Barents Sea. The scientific motivations of the study are (1) to document glacial landforms on a meter-scale, (2) to study ...
    • Ice‐rafting patterns on the western Svalbard slope 74–0 ka: interplay between ice‐sheet activity, climate and ocean circulation 

      Jessen, Simon Pind; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Preprint; Manuskript, 2018-11-14)
      The distribution of ice‐rafted detritus (IRD) is studied in three cores from the western Svalbard slope (1130–1880 m water depth, 76–78°N) covering the period 74–0 ka. The aim was to provide new insight into the dynamics of the Svalbard–Barents Sea Ice Sheet during Marine Isotope Stages (MIS) 4–1 to get a better understanding of ice‐sheet interactions with changes in ocean circulation and climate ...
    • Identifying past petroleum exploration related drill cutting releases and influences on the marine environment and benthic foraminiferal communities, Goliat Field, SW Barents Sea, Norway 

      Sørensen, Steffen Aagaard; Junttila, Juho; Dijkstra, Noortje (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-01)
      The present multiproxy investigation of marine sediment cores aims at: 1) Identifying dispersion of petroleum exploration related drill cutting releases within the Goliat Field, Barents Sea in 2006/07 and 2) Assessing past and present influence of drill cuttings on the marine environment. The cores were recovered 5, 30, 60, 125 and 250 m from the drill site in the eastward downstream direction.<p> ...
    • Image based quantitative comparisons indicate heightened megabenthos diversity and abundance at a site of weak hydrocarbon seepage in the southwestern Barents Sea 

      Sen, Arunima; Chitkara, Chestaa; Hong, Wei-Li; Lepland, Aivo; Cochrane, Sabine; Di Primio, Rolando; Brunstad, Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-08)
      <p><i>Background - </i>High primary productivity in the midst of high toxicity defines hydrocarbon seeps; this feature usually results in significantly higher biomass, but in lower diversity communities at seeps rather than in the surrounding non-seep benthos. Qualitative estimates indicate that this dichotomy does not necessarily hold true in high latitude regions with respect to megafauna. Instead, ...
    • Impact of Arctic shelf summer stratification on Holocene climate variability 

      Thibodeau, Benoit; Bauch, Henning A.; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-21)
      Understanding the dynamic of freshwater and sea-ice export from the Arctic is crucial to better comprehend the potential near-future climate change consequences. Here, we report nitrogen isotope data of a core from the Laptev Sea to shed light on the impact of the Holocene Siberian transgression on the summer stratification of the Laptev Sea. Our data suggest that the oceanographic setting was ...
    • Impact of natural (waves and currents) and anthropogenic (trawl) resuspension on the export of particulate matter to the open ocean: Application to the Gulf of Lion (NW Mediterranean) 

      Ferré, Bénédicte; Durrieu de Madron, X.; Estournel, C.; Ulses, G.; Le Corre, G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2008-02-17)
      <p>Modern sediment deposits on continental margins form a vast reservoir of particulate matter that is regularly affected by resuspension processes. Resuspension by bottom trawling on shelves with strong fishing activity can modify the scale of natural disturbance by waves and currents. Recent field data show that the impact of bottom trawls on fine sediment resuspension per unit surface is comparable ...
    • The impact of submarine copper mine tailing disposal from the 1970s on Repparfjorden, northern Norway 

      Sternal, Beata; Junttila, Juho; Skirbekk, Kari; Forwick, Matthias; Carroll, JoLynn; Pedersen, Kristine Bondo (Journal article; Tidsskriftartikkel, 2017-05-10)
      We investigate the state of sedimentological environment and contaminant status of Repparfjorden (N Norway) impacted by submarine disposal of mine tailings during the 1970s using sedimentological and geochemical properties of seventeen sediment cores. The impact of tailings disposal is mainly restricted to the inner fjord where the discharge occurred. Sediment cores retrieved from the inner fjord ...
    • Impact of Timanian thrusts on the Phanerozoic tectonic history of Svalbard 

      Koehl, Jean-Baptiste P. (Conference object; Konferansebidrag; Preprint, 2019-09-13)
      Despite more than a century of investigation, the relationship between basement rocks throughout the Svalbard Archipelago is still a mystery. Though these rocks display similar geochronological ages, they show significantly different metamorphic grades and structures. Thus far, Svalbard was believed to be composed of three terranes of rocks formed hundreds–thousands of kilometers apart and accreted ...
    • In Situ Temperature Measurements at the Svalbard Continental Margin: Implications for Gas Hydrate Dynamics 

      Riedel, M.; Wallmann, K.; Berndt, C; Pape, T.; Freudenthal, T.; Bergenthal, M.; Bünz, Stefan; Bohrmann, G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-30)
      During expedition MARIA S. MERIAN MSM57/2 to the Svalbard margin offshore Prins Karls Forland, the seafloor drill rig MARUM‐MeBo70 was used to assess the landward termination of the gas hydrate system in water depths between 340 and 446 m. The study region shows abundant seafloor gas vents, clustered at a water depth of ∼400 m. The sedimentary environment within the upper 100 m below seafloor (mbsf) ...
    • The influence of a model subglacial lake on ice dynamics and internal layering 

      Gudlaugsson, Eythor; Humbert, Angelika; Kleiner, Thomas; Kohler, Jack; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-05)
      As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic ...
    • The influence of Coriolis force driven water circulation on the palaeoenvironment of Hornsund (S Spitsbergen) over the last century 

      Pawłowska, Joanna; Zajączkowski, Marek; Szczuciński, Witold; Zaborska, Agata; Kucharska, Małgorzata; Jernas, Patrycja Ewa; Forwick, Matthias (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-22)
      The influence of the Coriolis force on the Hornsund fjord environment (southern Spitsbergen) was investigated in the marine sedimentary record from the last century. Due to the influence of the rotational effects, Atlantic and Arctic Water enter the fjord along the southern shore and exit along the northern shore. Thus, the sedimentary record from the southern part reflects the large‐scale hydrological ...
    • The inheritance of a Mesozoic landscape in western Scandinavia 

      Fredin, Ola; Viola, Giulio; Zwingmann, Horst; Sørlie, Ronald; Brönner, Marco; Lie, Jan-Erik; Grandal, Else Margrethe; Müller, Axel Bernd; Margreth, Annina; Vogt, Christoph; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-28)
      In-situ weathered bedrock, saprolite, is locally found in Scandinavia, where it is commonly thought to represent pre-Pleistocene weathering possibly associated with landscape formation. The age of weathering, however, remains loosely constrained, which has an impact on existing geological and landscape evolution models and morphotectonic correlations. Here we provide new geochronological evidence ...
    • An integrated view of the methane system in the pockmarks at Vestnesa Ridge, 79°N 

      Panieri, Giuliana; Bünz, Stefan; Fornari, Daniel J.; Escartin, Javier; Serov, Pavel; Jansson, Pär; Torres, Marta E.; Hong, Wei-Li; Sauer, Simone; Garcia, Rafael; Gracias, Nuno (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-08)
      The Vestnesa Ridge is a NW-SE trending, ~ 100 km-long, 1–2 km-thick contourite sediment section located in the Arctic Ocean, west of Svalbard, at 79°N. Pockmarks align along the ridge summit at water depths of ~ 1200 m; they are ~ 700 m in diameter and ~ 10 m deep relative to the surrounding seafloor. Observations of methane seepage in this area have been reported since 2008. Here we summarize and ...
    • Ionospheric Response Observed by EISCAT During the 6–8 September 2017 Space Weather Event: Overview 

      Yamauchi, M; Sergiengko, Timothy; Enell, Carl-Fredrik; Schillings, A.; Slapak, R.; Johnsen, Magnar Gullikstad; Tjulin, A.; Nilsson, H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-03)
      We present ionospheric plasma conditions observed by the EISCAT radars in Tromsø and on Svalbard, covering 68°–81° geomagnetic latitude, during 6–8 September 2017. This is a period when X2.2 and X9.3 X‐ray flares occurred, two interplanetary coronal mass ejections (ICMEs) arrived at the Earth accompanied by enhancements of MeV‐range energetic particle flux in both the solar wind (SEP event) and inner ...
    • K-Ar illite and apatite fission track constraints onbrittle faulting and the evolution of the northern Norwegian passive margin 

      Davids, Corine; Wemmer, Klaus; Zwingmann, Horst; Kohlmann, Fabian; Jacobs, Joachim; Bergh, Steffen G (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Determining the timing of post-Caledonian brittle faulting in northern Norway is important for the understanding of the extensional tectonic evolution of the north Norwegian continental margin. Fault gouges from the Troms and Vesterålen regions of northern Norway yield Carboniferous to Permian and Carboniferous to Cretaceous K–Ar illite ages, respectively. The results show a contrast in fault activity ...
    • Keystone Arctic paleoceanographic proxy association with putative methanotrophic bacteria 

      Bernhard, Joan M.; Panieri, Giuliana (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-13)
      Foraminifera in sediments exposed to gas-hydrate dissociation are not expected to have cellular adaptations that facilitate inhabitation of chemosynthesis-based ecosystems because, to date, there are no known endemic seep foraminifera. To establish if foraminifera inhabit sediments impacted by gas-hydrate dissociation, we examined the cellular ultrastructure of <i>Melonis barleeanus</i> (Williamson, ...
    • Labilibaculum manganireducens gen. nov., sp. nov. and Labilibaculum filiforme sp. nov., Novel Bacteroidetes Isolated from Subsurface Sediments of the Baltic Sea 

      Vandieken, Verona; Marshall, Ian P.G.; Niemann, Helge; Engelen, Bert; Cypionka, Heribert (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-05)
      Microbial communities in deep subsurface sediments are challenged by the decrease in amount and quality of organic substrates with depth. In sediments of the Baltic Sea, they might additionally have to cope with an increase in salinity from ions that have diffused downward from the overlying water during the last 9000 years. Here, we report the isolation and characterization of four novel bacteria ...
    • Large subglacial meltwater features in the central Barents Sea 

      Bjarnadóttir, Lilja Rún; Winsborrow, Monica; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-01)
      During the last glacial period large parts of the Arctic, including the Barents Sea, north of Norway and Russia, were covered by ice sheets. Despite several studies indicating that melting occurred beneath much of the Barents Sea ice sheet, very few meltwater-related landforms have been identified. We document ∼200 seafloor valleys in the central Barents Sea and interpret them to be tunnel valleys ...
    • The last 2 Myr of accretionary wedge construction in the central Hikurangi margin (North Island, New Zealand): Insights from structural modeling 

      Ghisetti, Francesca C.; Barnes, Philip M.; Ellis, Susan; Plaza-Faverola, Andreia; Barker, Daniel H.N. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-07-17)
      Three depth-converted and geologically interpreted seismic profiles provide a clear image of the offshore outer accretionary wedge associated with oblique subduction of the Pacific Plate beneath the central Hikurangi margin. Plio-Quaternary turbidites deposited over the pelagic cover sequence of the Hikurangi Plateau have been accreted to the margin by imbrication along E-verging thrust faults that ...