Now showing items 1-20 of 588

    • 1.80–1.75 Ga granite suites in the west Troms Basement Complex, northern Norway: Palaeoproterozoic magma emplacement during advancing accretionary orogeny, from field observations 

      Bergh, Steffen Gunnar; Haaland, Linda Cecilia; Arbaret, L.; Coint, Nolwenn; Forien, Melanie (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-25)
      The Ersfjord Granite is part of a suite of c.1.80–1.75 Ga syeno-granites in the West Troms Basement Complex, northern Norway, presumed to belong to the Transscandinavian Igneous Belt (TIB-1) in the Fennoscandian Shield. Previous data suggest the granite formed post-collisional and ascended as a batholith pluton from a source generated by delamination of mafic-intermediate lower crust. We argue that ...
    • A 160,000-year-old history of tectonically controlled methane seepage in the Arctic 

      Himmler, Tobias; Sahy, Diana; Martma, Tõnu; Bohrmann, Gerhard; Plaza-Faverola, Andreia; Bünz, Stefan; Condon, Daniel J.; Knies, Jochen; Lepland, Aivo (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-07)
      The geological factors controlling gas release from Arctic deep-water gas reservoirs through seabed methane seeps are poorly constrained. This is partly due to limited data on the precise chronology of past methane emission episodes. Here, we use uranium-thorium dating of seep carbonates sampled from the seabed and from cores drilled at the Vestnesa Ridge, off West Svalbard (79°N, ~1200 m water ...
    • 3D Seismic Investigation of a Gas Hydrate and Fluid Flow System on an Active Mid‐Ocean Ridge; Svyatogor Ridge, Fram Strait 

      Waghorn, Kate Alyse; Bünz, Stefan; Plaza-Faverola, Andreia; Johnson, Joel E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-12)
      Tectonic settings play a large role in the development of fluid flow pathways for gas migrating through sedimentary strata. Many gas hydrate systems worldwide are located on either passive continental margins, in large contourite deposits on the slopes of passive continental margins or on subduction margins. The Svyatogor Ridge, however, located at the northwestern flank of the Knipovich Ridge and ...
    • Abiotic methane from ultraslow-spreading ridges can charge Arctic gas hydrates 

      Johnson, Joel E; Mienert, Jurgen; Plaza-Faverola, Andreia; Vadakkepuliyambatta, Sunil; Knies, Jochen; Bünz, Stefan; Andreassen, Karin; Ferré, Benedicte (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-05)
      Biotic gas generation from the degradation of organic carbon in marine sediments supplies and maintains gas hydrates throughout the world’s oceans. In nascent, ultraslow-spreading ocean basins, methane generation can also be abiotic, occurring during the high-temperature (>200 °C) serpentinization of ultramafic rocks. Here, we report on the evolution of a growing Arctic gas- and gas hydrate–charged ...
    • Acoustic generation of underwater cavities - Comparing modeled and measured acoustic signals generated by seismic air gun arrays 

      Khodabandeloo, Babak; Landrø, Martin; Hanssen, Alfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-14)
      Underwater vapor cavities can be generated by acoustic stimulation. When the acoustic signals from several air guns are reflected from the sea surface, the pressure drop at some locations is sufficient for cavity growth and subsequent collapse. In this paper the generation of multiple water vapor cavities and their collapses are numerically modeled and the results are validated by comparing with ...
    • Adamastor – an ocean that never existed? 

      Konopasek, Jiri; Cavalcante, Carolina; Fossen, Haakon; Janoušek, Vojtěch (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-08)
      <p>Existing models of tectonic evolution of the Neoproterozoic orogenic system rimming the shores of the South Atlantic Ocean (the Araçuaí–Ribeira–Congo and Dom Feliciano–Kaoko–Gariep belts) interpret the belts as subduction-related orogens and emphasize the role of the “Adamastor Ocean” in their pre-collisional evolution. A critical problem in such an interpretation is the confined nature of the ...
    • Aligned glaciotectonic rafts on the central Barents Sea seafloor revealing extensive glacitectonic erosion during the last deglaciation 

      Ruther, Denise Christina; Andreassen, Karin; Spagnolo, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-12-07)
      Erosion rates on glaciated continental shelves are remarkably high, especially within ice stream troughs. Although glaciotectonic erosion may have considerably contributed to enhanced glacial erosion of these landscapes, entrainment mechanisms of glaciotectonically emplaced megablocks and rafts remain little understood. Here we report a northeast-southwest trending chain of over 1300 glacial rafts, ...
    • Amino acid racemization in Quaternary foraminifera from the Yermak Plateau, Arctic Ocean 

      West, Gabriel; Kaufman, Darrell S; Muschitiello, Francesco; Forwick, Matthias; Matthiessen, Jens; Wollenburg, Jutta; O’Regan, Matt (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-18)
      Amino acid racemization (AAR) geochronology is a powerful tool for dating Quaternary marine sediments across the globe, yet its application to Arctic Ocean sediments has been limited. Anomalous rates of AAR in foraminifera from the central Arctic were reported in previously published studies, indicating that either the rate of racemization is higher in this area, or inaccurate age models were used ...
    • Ammonium and Sulfate Assimilation Is Widespread in Benthic Foraminifera 

      LeKieffre, Charlotte; Jauffrais, Thierry; Bernhard, Joan M.; Filipsson, Helena L.; Schmidt, Christiane; Roberge, Helene; Maire, Olivier; Panieri, Giuliana; Geslin, Emmanuelle; Meibom, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-20)
      Nitrogen and sulfur are key elements in the biogeochemical cycles of marine ecosystems to which benthic foraminifera contribute significantly. Yet, cell-specific assimilation of ammonium, nitrate and sulfate by these protists is poorly characterized and understood across their wide range of species-specific trophic strategies. For example, detailed knowledge about ammonium and sulfate assimilation ...
    • Amorphous material in experimentally deformed mafic rock and its temperature dependence: Implications for fault rheology during aseismic creep and seismic rupture 

      Marti, Sina; Stünitz, Holger; Heilbronner, Renee; Plümper, Oliver (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-20)
      Amorphous materials are frequently observed in natural and experimentally produced fault rocks. Their common occurrence suggests that amorphous materials are of importance to fault zone dynamics. However, little is known about the physico-chemical impact of amorphous materials on fault rheology. Here we present deformation experiments on mafic fault rock, where amorphous material forms due to intense ...
    • An annual profile of the impacts of simulated oil spills on the Northeast Arctic cod and haddock fisherie 

      Carroll, JoLynn; Frøysa, Håvard Guldbrandsen; Vikebø, Frode Bendiksen; Broch, Ole Jacob; Nepstad, Raymond; Augustine, Starrlight; Skeie, Geir Morten; Bockwoldt, Mathias; Howell, Daniel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-10)
      We simulate the combined natural and pollutant-induced survival of early life stages of NEA cod and haddock, and the impact on the adult populations in response to the time of a major oil spill in a single year. Our simulations reveal how dynamic ocean processes, controlling both oil transport and fate and the frequency of interactions of oil with drifting fish eggs and larvae, mediate the magnitude ...
    • An annual profile of the impacts of simulated oil spills on the Northeast Arctic cod and haddock fisheries 

      Carroll, JoLynn; Frøysa, Håvard Guldbrandsen; Vikebø, Frode Bendiksen; Broch, Ole Jacob; Howell, Daniel; Nepstad, Raymond; Augustine, Starrlight; Skeie, Geir Morten; Bockwoldt, Mathias (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-10)
      We simulate the combined natural and pollutant-induced survival of early life stages of NEA cod and haddock, and the impact on the adult populations in response to the time of a major oil spill in a single year. Our simulations reveal how dynamic ocean processes, controlling both oil transport and fate and the frequency of interactions of oil with drifting fish eggs and larvae, mediate the magnitude ...
    • Anthropocene rockfalls travel farther than prehistoric predecessors 

      Vick, Louise Mary; Borella, Josh Walter; Quigley, Mark (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-02)
      Human modification of natural landscapes has influenced surface processes in many settings on Earth. Quantitative data comparing the distribution and behavior of geologic phenomena before and after human arrival are sparse but urgently required to evaluate possible anthropogenic influences on geologic hazards. We conduct field and imagery-based mapping, statistical analysis, and numerical modeling ...
    • Anticlockwise metamorphic pressure–temperature paths and nappe stacking in the Reisa Nappe Complex in the Scandinavian Caledonides, northern Norway: evidence for weakening of lower continental crust before and during continental collision 

      Faber, Carly; Stunitz, Holger; Gasser, Deta; Jeřábek, Petr; Kraus, Katrin; Corfu, Fernando; Ravna, Erling Krogh; Konopásek, Jiří (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
      This study investigates the tectonostratigraphy and metamorphic and tectonic evolution of the Caledonian Reisa Nappe Complex (RNC; from bottom to top: Vaddas, Kåfjord, and Nordmannvik nappes) in northern Troms, Norway. Structural data, phase equilibrium modelling, and U-Pb zircon and titanite geochronology are used to constrain the timing and pressure–temperature (<i>P–T</i>) conditions of deformation ...
    • Arctic and sub-Arctic lake water δ2H and δ18O along a coastal-inland transect: Implications for interpreting water isotope proxy records 

      Kjellman, Sofia Elisabeth; Thomas, Elizabeth K.; Schomacker, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-04)
      High-latitude lakes are sensitive to climate change and store information about large-scale circulation changes and catchment-integrated processes. Lakes are mainly recharged by meteoric water, meaning that some lake sediment proxies may indirectly archive the stable isotopic composition of hydrogen (δ<sup>2</sup> H) and oxygen (δ<sup>18</sup>O) of past precipitation. Yet, despite similar ...
    • Arctic megaslide at presumed rest 

      Geissler, Wolfram H.; Gebhardt, Catalina; Gross, Felix; Wollenburg, Jutta; Jensen, Laura; Schmidt-Aursch, Mechita; Krastel, Sebastian; Elger, Judith; Osti, Giacomo (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope ...
    • Arctic Ocean glacial history 

      Jakobsson, Martin; Andreassen, Karin; Bjarnadóttir, Lilja Rún; Dove, Dayton; Dowdeswell, Julian A.; England, John H.; Funder, Svend; Hogan, Kelly; Ingólfsson, Ólafur; Jennings, Anne; Krog Larsen, Nikolaj; Kirchner, Nina; Landvik, Jon Y.; Mayer, Larry; Mikkelsen, Naja; Möller, Per; Niessen, Frank; Nilsson, Johan; O'Reagan, Matt; Polyak, Leonid; Nørgaard-Pedersen, Niels; Stein, Ruediger (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-11-14)
      While there are numerous hypotheses concerning glacial–interglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the ...
    • Arctic sea-ice loss fuels extreme European snowfall 

      Bailey, Hannah L.; Hubbard, Alun Lloyd; Klein, Eric S.; Mustonen, Kaisa-Riikka; Akers, Pete D.; Marttila, Hannu; Welker, Jeffrey M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-01)
      The loss of Arctic sea-ice has been implicated with severe cold and snowy mid-latitude winters. However, the mechanisms and a direct link remain elusive due to limited observational evidence. Here we present atmospheric water vapour isotope measurements from Arctic Finland during ‘the Beast from the East’—a severe anticyclonic outbreak that brought heavy snowfall and freezing across Europe in February ...
    • Area and volume of mid-latitude glacier-like forms on Mars 

      Brough, Stephen; Hubbard, Bryn; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-04)
      Although a substantial ice cover has been identified within the mid-latitudes of Mars, there is uncertainty regarding the formation, current and former volume, and dynamic evolution of these ice masses. Here, we present the first comprehensive ice volume estimate of martian glacier-like forms (GLFs) from systematic population scale mapping and volumetric analysis. The outlines of 1243 GLFs were ...
    • Assessing impacts of simulated oil spills on the Northeast Arctic cod fishery 

      Carroll, JoLynn; Vikebø, Frode Bendiksen; Howell, Daniel; Broch, OJ; Nepstad, Raymond; Augustine, Starrlight; Skeie, Geir Morten; Bast, Radovan; Juselius, Jonas (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-04)
      We simulate oil spills of 1500 and 4500 m3/day lasting 14, 45, and 90 days in the spawning grounds of the commercial fish species, Northeast Arctic cod. Modeling the life history of individual fish eggs and larvae, we predict deviations from the historical pattern of recruitment to the adult population due to toxic oil exposures. Reductions in survival for pelagic stages of cod were 0–10%, up to a ...