Viser treff 509-528 av 982

    • Magnetotelluric signatures of the complex tertiary fold–thrust belt and extensional fault architecture beneath Brøggerhalvøya, Svalbard 

      Beka, Thomas Ibsa; Bergh, Steffen G; Smirnov, Maxim; Birkelund, Yngve (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-18)
      Magnetotelluric (MT) data were recently collected on Brøggerhalvøya, Svalbard, in a 0.003–1000 s period range along a curved WNW–ESE profile. The collected data manifested strong three-dimensional (3D) effects. We modelled the full impedance tensor with tipper and bathymetry included in 3D, and benchmarked the result with determinant data two-dimensional (2D) inversion. The final inversion results ...
    • Manganese/iron‐supported sulfate‐dependent anaerobic oxidation of methane by archaea in lake sediments 

      Su, Guangyi; Zopfi, Jakob; Yao, Haoyi; Steinle, Lea; Niemann, Helge; Lehmann, Moritz F (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-04)
      Anaerobic oxidation of methane (AOM) by methanotrophic archaea is an important sink of this greenhouse gas in marine sediments. However, evidence for AOM in freshwater habitats is rare, and little is known about the pathways, electron acceptors, and microbes involved. Here, we show that AOM occurs in anoxic sediments of a sulfate‐rich lake in southern Switzerland (Lake Cadagno). Combined AOM‐rate ...
    • Mapping and characterization of unstable slopes with Sentinel-1 multi-geometry InSAR (activity line 2: public sector applications) 

      Lauknes, Tom Rune; Grahn, Jakob; Royet, Line; Larsen, Yngvar; Böhme, Martina; Dehls, John F.; Kristiansen, Lene (Research report; Forskningsrapport, 2020)
      This is a high-level report that summarizes the main achievements and results of the research and development conducted in the project “Mapping and Characterization of unstable slopes with Sentinel-1 multi-geometry InSAR (activity line 2: public sector applications)”, where multi-geometry Sentinel-1 Synthetic Aperture Radar Interferometry (InSAR) is used for improving characterization of unstable ...
    • Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2 levels 

      Pavlov, Alexey K.; Silyakova, Anna; Granskog, Mats A.; Bellerby, Richard; Engel, Anja; Schulz, Kai G.; Brussaard, Corina P. D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-05-22)
      A large-scale multidisciplinary mesocosm experiment in an Arctic fjord (Kongsfjorden, Svalbard; 78°56.2′N) was used to study Arctic marine food webs and biogeochemical elements cycling at natural and elevated future carbon dioxide (CO2) levels. At the start of the experiment, marine-derived chromophoric dissolved organic matter (CDOM) dominated the CDOM pool. Thus, this experiment constituted a ...
    • The marine sedimentary environments of Kongsfjorden, Svalbard: an archive of polar environmental change 

      Husum, Katrine; Howe, John A; Baltzer, Agnes; Forwick, Matthias; Jensen, Maria; Jernas, Patrycja; Korsun, Sergei; Miettinen, Arto; Mohan, Rahul; Morigi, Caterina; Myhre, Per Inge; Prins, Maarten A.; Skirbekk, Kari; Sternal, Beata; Boos, Michel; Dijkstra, Noortje; Troelstra, Simon R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-16)
      Kongsfjorden, a fjord in north-western Svalbard, is characterized by large environmental gradients driven by meltwater processes along the margins of tidewater glaciers and the inflow of relatively warm Atlantic Water, the main heat source for the European Arctic. These factors make Kongsfjorden a key area to investigate changes in the polar climate–ocean–glacier system and to examine the resulting ...
    • Mechanical properties and recrystallization of quartz in presence of H<inf>2</inf>O: Combination of cracking, subgrain rotation and dissolution-precipitation processes 

      Pongrac, Petar; Jeřábek, Petr; Stunitz, Holger; Raimbourg, Hugues; Heilbronner, Renee; Racek, Martin; Nègre, Lucille (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-21)
      Natural quartzite samples, as-is and with 0.1 wt% of added H<sub>2</sub>O, have been deformed up to ∼30% bulk strain in axial shortening experiments with constant strain rate of ∼10<sup>−6</sup> s<sup>−1</sup> at 900 °C and 1 GPa, and in strain rate stepping ∼10<sup>−5</sup> to ∼10<sup>−7</sup> s<sup>−1</sup> at 900 °C and 1–1.5 GPa, in order to investigate the role of H<sub>2</sub>O in deformation ...
    • Metamorf utvikling av Skagen-eklogitt, Flakstadøy, Lofoten 

      Bakkejord, Sandra Johansen (Master thesis; Mastergradsoppgave, 2011-05)
      Bergartsprøver fra Skagen på Flakstadøy, Lofoten er mikroskopert, analysert ved mikrosonde og gjort geotermobarometriske estimat på, alt for å kunne fortelle om den metamorfe utviklingen for bergartene. Resultatene forteller om en polymorf utviklingshistorie av de proterozoiske bergartene som Flakstadøy er bygd opp av. Flere eklogittforekomster er funnet på øyen, noe som ikke er så overraskende da ...
    • Metamorphic conditions in the Coastal-Punta del Este Terrane of the Kaoko-Dom Feliciano Belt in Namibia and Uruguay 

      Skagseth, Ida Grindal (Master thesis; Mastergradsoppgave, 2016-06-24)
      The metasediementary rocks of the Coastal Terrane in the Kaoko Belt (Namibia) and the meta-igneous rocks of the Punta del Este-Terrane in the Dom Feliciano Belt (Uruguay) both share one high-grade metamorphic event at approximately the same time of c. 650-630 Ma. Metamorphic conditions of this high-grade event were estimated in four samples from the Punta del Este Terrane and two samples from ...
    • Metamorphic evolution in external zones of the Dom Feliciano-Kaoko orogenic system. Examples from the Brusque Metamorphic Complex, Dom Feliciano Belt (Brazil) and the Central Kaoko Zone, Kaoko Belt (Namibia) 

      Asvald, Caroline (Master thesis; Mastergradsoppgave, 2018-05-15)
      The Brusque Metamorphic Complex in the Dom Feliciano Belt (Brazil) and the Central Kaoko Zone in the Kaoko Belt (Namibia) represent foreland fold- and thrust belts in external parts of the northern Dom Feliciano-Kaoko orogenic system. Petrographic and field observations of metapelitic samples from the Brusque Metamorphic Complex suggests that the western part of the complex can be subdivided into ...
    • Metamorphic evolution of the Passo Feio Complex (central part of the Dom Feliciano Belt, southern Brazil) 

      Tennholm, Tonje (Master thesis; Mastergradsoppgave, 2019-05-15)
      The Passo Feio Complex is considered as a part of the São Gabriel Terrane, located to the west of the Dom Feliciano Belt in the state of Rio Grande do Sul (Brazil), but shows numerous similarities with the easterly exposed Porongos Metamorphic Complex which is a part of the Schist Belt in that area. P-T phase equilibrium modelling of metamorphosed sedimentary rocks from the Passo Feio Complex was ...
    • Meter-Scale 3D Seismic Data for High-Resolution Site Characterization 

      Lebedeva-Ivanova, Nina; Polteau, Stephane; Zastrozhnov, Dmitry; Planke, Sverre; Waage, Malin; Bünz, Stefan; Bellwald, Benjamin; Vanneste, Maarten; Sauvin, Guillaume; Myklebust, R. (Conference object; Konferansebidrag, 2019-06-03)
      High-resolution 3D site characterization can deliver reliable quantitative property volumes of the subsurface when based on seismic data able to image meter-sized objects. Following the theoretical analysis of seismic wave propagation in the shallow sub-surface, we present case studies based on re-processing of 3D P-Cable seismic data. The case study of data re-processing from the Vestnesa Ridge ...
    • Methane at Svalbard and over the European Arctic Ocean 

      Platt, Stephen Matthew; Eckhardt, Sabine; Ferré, Benedicte; Fisher, Rebecca E.; Hermansen, Ove; Jansson, Pär; Lowry, David; Nisbet, Euan G.; Pisso, Ignacio; Schmidbauer, Norbert; Silyakova, Anna; Stohl, Andreas; Svendby, Tove Marit; Vadakkepuliyambatta, Sunil; Mienert, Jurgen; Myhre, Cathrine Lund (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-05)
      Methane (CH<sub>4</sub>) is a powerful greenhouse gas. Its atmospheric mixing ratios have been increasing since 2005. Therefore, quantification of CH<sub>4</sub> sources is essential for effective climate change mitigation. Here we report observations of the CH<sub>4</sub> mixing ratios measured at the Zeppelin Observatory (Svalbard) in the Arctic and aboard the research vessel (RV) Helmer Hanssen ...
    • Methane cold seeps as biological oases in the high-Arctic deep sea 

      Åström, Emmelie; Carroll, Michael Leslie; Ambrose, William; Sen, Arunima; Silyakova, Anna; Carroll, JoLynn (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-27)
      Cold seeps can support unique faunal communities via chemosynthetic interactions fueled by seabed emissions of hydrocarbons. Additionally, cold seeps can enhance habitat complexity at the deep seafloor through the accretion of methane derived authigenic carbonates (MDAC). We examined infaunal and megafaunal community structure at high-Arctic cold seeps through analyses of benthic samples and ...
    • Methane hydrate formation in Ulleung basin under conditions of variable salinity: reduced model and experiments 

      Peszynska, Malgorzata; Hong, Wei-Li; Torres, Marta E.; Kim, Ji-Hoon (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-06-13)
      In this paper, we present a reduced model of methane hydrate formation in variable salinity conditions, with details on the equilibrium phase behavior adapted to a case study from Ulleung Basin. The model simplifies the comprehensive model considered by Liu and Flemings using common assumptions on hydrostatic pressure, geothermal gradient, and phase incompressibility, as well as a simplified ...
    • Methane release from open leads and new ice following an Arctic winter storm event 

      Silyakova, Anna; Nomura, Daiki; Kotovitch, Marie; Fransson, Agneta; Delille, Bruno; Chierici, Melissa; Granskog, Mats A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-03)
      We examine an Arctic winter storm event, which led to ice break–up, the formation of open leads, and the subsequent freezing of these leads. The methane (CH<sub>4</sub>) concentration in under–ice surface water before and during the storm event was 8–12 nmol L<sup>−1</sup>, which resulted in a potential sea–to–air CH<sub>4</sub> flux ranging from +0.2 to +2.1 mg CH<sub>4</sub> m<sup>−2</sup> ...
    • Methane release from pingo-like features across the South Kara Sea shelf, an area of thawing offshore permafrost 

      Serov, Pavel; Portnov, Aleksei D; Mienert, Jurgen; Semenov, Peter; Ilatovskaya, Polonia (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-16)
      The Holocene marine transgression starting at ~19 ka flooded the Arctic shelves driving extensive thawing of terrestrial permafrost. It thereby promoted methanogenesis within sediments, the dissociation of gas hydrates, and the release of formerly trapped gas, with the accumulation in pressure of released methane eventually triggering blowouts through weakened zones in the overlying and thinned ...
    • Methane seepage at Vestnesa Ridge (NW Svalbard) since the Last Glacial Maximum 

      Schneider, Andrea; Panieri, Giuliana; Lepland, Aivo; Consolaro, Chiara; Crémière, Antoine; Forwick, Matthias; Johnson, J.E.; Plaza-Faverola, Andreia; Sauer, Simone; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-21)
      <p>Multiple proxies in the geological record offshore NW Svalbard track shallow subseafloor diagenesis and seafloor methane seepage during the Last Glacial Maximum (LGM) extent and the disintegration of the Svalbard Barents Sea Ice Sheet (SBIS). Vestnesa Ridge, located at 79°N and in 1200 m water depth, is one of the northernmost known active methane seep sites and is characterised by a subseafloor ...
    • Methane transport and sources in an Arctic deep-water cold seep offshore NW Svalbard (Vestnesa Ridge, 79°N) 

      Sauer, Simone; Hong, Wei-Li; Yao, Haoyi; Lepland, Aivo; Klug, Martin; Eichinger, Florian; Himmler, Tobias; Cremiere, Antoine; Panieri, Giuliana; Schubert, Carsten J.; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-29)
      We investigate the uppermost 60 cm of sediment in active pockmarks of a deep-water methane seep site from Vestnesa Ridge offshore NW Svalbard. Using video guided core sampling with a remotely operated vehicle we collected push cores directly from bacterial mats within two active pockmarks, Lunde and Lomvi. Pore water analyses show very shallow sulphate methane transition zones and transport-reaction ...
    • Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem 

      Brankovits, D.; Pohlman, J.W.; Niemann, Helge; Leigh, M.B.; Leewis, M.C.; Becker, K.W.; Iliffe, F.A.; Lehmann, M.F.; Phillips, B. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-28)
      Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment is poorly understood. Here, we demonstrate that a microbial loop shuttles methane and dissolved organic ...
    • Methane-fuelled biofilms predominantly composed of methanotrophic ANME-1 in Arctic gas hydrate-related sediments 

      Gründger, Friederike; Carrier, Vincent; Svenning, Mette Marianne; Panieri, Giuliana; Vonnahme, Tobias R.; Klasek, Scott; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-05)
      Sedimentary biofilms comprising microbial communities mediating the anaerobic oxidation of methane are rare. Here, we describe two biofilm communities discovered in sediment cores recovered from Arctic cold seep sites (gas hydrate pingos) in the north-western Barents Sea, characterized by steady methane fluxes. We found macroscopically visible biofilms in pockets in the sediment matrix at the depth ...