• 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 ...
    • Absence of photophysiological response to iron addition in autumn phytoplankton in the Antarctic sea-ice zone 

      Singh, Asmita; Fietz, Susanne; Thomalla, Sandy J.; Sanchez, Nicolas; Ardelan, Murat V.; Moreau, Sebastian; Kauko, Hanna Maria; Fransson, Agneta; Chierici, Melissa; Samanta, Saumik; Mtshali, Thato N.; Roychoudhury, Alakendra N.; Ryan-Keogh, Thomas J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-31)
      he high nutrient–low chlorophyll condition of the Southern Ocean is generally thought to be caused by the low bioavailability of micronutrients, particularly iron, which plays an integral role in phytoplankton photosynthesis. Nevertheless, the Southern Ocean experiences seasonal blooms that generally initiate in austral spring, peak in summer, and extend into autumn. This seasonal increase in primary ...
    • 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 ...
    • Active Nordic Seas deep-water formation during the last glacial maximum 

      Larkin, Christina S.; Mohamed, Mohamed Mahmoud Ezat Ahmed; Roberts, Natalie L.; Bauch, Henning A.; Spielhagen, Robert F.; Noormets, Riko; Polyak, Leonid; Moreton, Steven G.; Rasmussen, Tine Lander; Sarnthein, Michael; Tipper, Edward T.; Piotrowski, Alex M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-24)
      The Nordic Seas are the primary location where the warm waters of the North Atlantic Current densify to form North Atlantic Deep Water, which plays a key part in the modern Atlantic Meridional Overturning Circulation. The formation of dense water in the Nordic Seas and Arctic Ocean and resulting ocean circulation changes were probably driven by and contributed to the regional and global climate of ...
    • 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 ...
    • Advances in understanding subglacial meltwater drainage from past ice sheets 

      Simkins, Lauren M; Greenwood, Sarah L.; Winsborrow, Monica; Bjarnadóttir, Lilja Rún; Lepp, Allison (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-17)
      Meltwater drainage beneath ice sheets is a fundamental consideration for understanding ice–bed conditions and bed-modulated ice flow, with potential impacts on terminus behavior and iceshelf mass balance. While contemporary observations reveal the presence of basal water movement in the subglacial environment and inferred styles of drainage, the geological record of former ice sheets, including ...
    • 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 ...
    • Arc-like magmatism in syn- to post-collisional setting: The Ediacaran Angra Fria Magmatic Complex (NW Namibia) and its cross-Atlantic correlatives in the south Brazilian Florianópolis Batholith 

      Janousek, Vojtěch; Florisbal, Luana Moreira; Konopásek, Jiří; Jeřábek, Petr; Bitencourt, Maria de Fatima; Gadas, Petr; Erban, Vojtěch; Kopačková-Strnadová, Veronika (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-27)
      Ediacaran syn-tectonic plutonic rocks (amphibole gabbros, quartz diorites/tonalites to biotite- and muscovite-bearing granites) of the Angra Fria Magmatic Complex (Kaoko Belt, north-western Namibia) belong to two compositionally similar, magnesian, transitional tholeiitic–calc-alkaline suites, the Older (∼625–620 Ma) and the Younger (∼585–575 Ma). Both have counterparts in the broadly contemporaneous ...
    • 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 ...
    • An Arctic natural oil seep investigated from space to the seafloor 

      Panieri, Giuliana; Argentino, Claudio; Ramalho, Sofia P.; Vulcano, Francesca; Savini, Alessandra; Fallati, Luca; Brekke, Trond; Galimberti, Giulia; Riva, Federica; Balsa, João; Eilertsen, Mari Heggernes; Stokke, Runar; Steen, Ida Helene; Sahy, Diana; Kalenitchenko, Dimitri Stanislas Desire; Bünz, Stefan; Mattingsdal, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-19)
      Due to climate change, decreasing ice cover and increasing industrial activities, Arctic marine ecosystems are expected to face higher levels of anthropogenic stress. To sustain healthy and productive ocean ecosystems, it is imperative to build baseline data to assess future changes. Herein, a natural oil seep site offshore western Svalbard (Prins Karls Forland, PKF, 80–100 m water depth), discovered ...
    • 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 ...