Now showing items 1-20 of 300

    • 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 ...
    • 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 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 ...
    • 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 ...
    • An assessment of biomarker-based multivariate classification methods versus the PIP25 index for paleo Arctic sea ice reconstruction 

      Koseoglu, Denizcan; Belt, Simon T.; Husum, Katrine; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-30)
      The development of various combinative methods for Arctic sea ice reconstruction using the sympagic highly-branched isoprenoid (HBI) IP<sub>25</sub> in conjunction with pelagic biomarkers has often facilitated more detailed descriptions of sea ice conditions than using IP<sub>25</sub> alone. Here, we investigated the application of the Phytoplankton-IP<sub>25</sub> index (PIP<sub>25</sub>) and a ...
    • Assessment of offshore wind power potential in the Aegean and Ionian<br> Seas based on high-resolution hindcast model results 

      Soukissian, Takvor; Papadopoulos, Anastasios; Skrimizeas, Panagiotis; Karathanasi, Flora; Axaopoulos, Panagiotis; Avgoustoglou, Evripides; Kyriakidou, Hara; Tsalis, Christos; Voudouri, Antigoni; Gofa, Flora; Katsafados, Petros (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-20)
      In this study long-term wind data obtained from high-resolution hindcast simulations is used to analytically assess offshore wind power potential in the Aegean and Ionian Seas and provide wind climate and wind power potential characteristics at selected locations, where offshore wind farms are at the concept/planning phase. After ensuring the good model performance through detailed validation against ...
    • Asynchronous response of marine-terminating outlet glaciers during deglaciation of the Fennoscandian Ice Sheet 

      Stokes, Chris R.; Corner, Geoffrey D.; Winsborrow, Monica; Husum, Katrine; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-03-31)
      Recent studies have highlighted the dynamic behavior of marine-terminating outlet glaciers over decadal time scales, linked to both atmospheric and oceanic warming. This helps explain episodes of nearly synchronous fl ow acceleration, thinning, and retreat, but nonclimatic factors such as changes in fjord width and depth, can also induce rapid recession. There is support for these topographic ...
    • Atypical biological features of a new cold seep site on the LofotenVesterålen continental margin (northern Norway) 

      Sen, Arunima; Himmler, Tobias; Hong, Wei-Li; Chitkara, Cheshtaa; Lee, Raymond W.; Ferré, Benedicte; Lepland, Aivo; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-11)
      A newly discovered cold seep from the Lofoten-Vesterålen margin (Norwegian Sea) is dominated by the chemosymbiotrophic siboglinid <i>Oligobrachia haakonmosbiensis</i> like other high latitude seeps, but additionally displays uncharacteristic features. Sulphidic bottom water likely prevents colonization by cnidarians and sponges, resulting in fewer taxa than deeper seeps in the region, representing ...
    • Authigenesis of biomorphic apatite particles from Benguela upwelling zone sediments off Namibia: The role of organic matter in sedimentary apatite nucleation and growth 

      Mänd, Kaarel; Kirsimäe, Kalle; Lepland, Aivo; Crosby, Chris H.; Bailey, Jake V.; Konhauser, Kurt O.; Wirth, Richard; Schreiber, Anja; Lumiste, Kaarel (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-30)
      Sedimentary phosphorites comprise a major phosphorus (P) ore, yet their formation remains poorly understood. Extant polyphosphate‐metabolizing bacterial communities are known to act as bacterial phosphate‐pumps, leading to episodically high dissolved phosphate concentrations in pore waters of organic‐rich sediment. These conditions can promote the precipitation of amorphous precursor phases that are ...
    • BedMachine v3: Complete bed topography and ocean bathymetry mapping of Greenland from multi-beam echo sounding combined with mass conservation 

      Morlighem, Mathieu; Williams, Chris N.; Rignot, Eric J.M.; An, Lu; Arndt, Jan Erik; Bamber, Jonathan L.; Catania, Ginny A.; Chauché, Nolwenn; Dowdeswell, Julian A.; Dorschel, Boris; Fenty, Ian; Hogan, Kelly A.; Howat, Ian M.; Hubbard, Alun Lloyd; Jakobsson, Martin; Jordan, Thomas M.; Kjeldsen, Kristian Kjellerup; Millan, Romain; Mayer, Larry; Mouginot, Jérémie; Noël, Brice P.Y.; O'Cofaigh, Colm; Palmer, Steven; Rysgaard, Søren; Seroussi, Hélène; Siegert, Martin J.; Slabon, Patricia; Straneo, Fiamma; van den Broeke, Michiel R.; Weinrebe, Wilhelm Reimer; Wood, Michael; Zinglersen, Karl Brix (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-18)
      Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine‐terminating glaciers. Here we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness ...
    • Benthic foraminifera as bio-indicators of chemical and physical stressors in Hammerfest harbor (Northern Norway) 

      Dijkstra, Noortje; Junttila, Juho; Skirbekk, Kari; Carroll, JoLynn; Husum, Katrine; Hald, Morten (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-01)
      We investigated benthic foraminiferal assemblages in contaminated sediments in a subarctic harbor of northern Norway to assess their utility as indicators of anthropogenic impacts. Sediments in the harbor are repositories for POPs and heavy metals supplied through discharges from industry and shipping activities. Sediment contaminant concentrations are at moderate to poor ecological quality ...
    • Benthic foraminiferal growth seasons implied from Mg/Ca-temperature correlations for three Arctic species 

      Skirbekk, Kari; Hald, Morten; Thomas Jr., Marchitto; Junttila, Juho; Klitgaard Kristensen, Dorthe; Sørensen, Steffen Aagaard (Peer reviewed, 2016-11-22)
      Core-top sediment samples from Kongsfjorden, Svalbard, and adjacent fjord and shelf areas were collected in order to investigate a potential relationship between Mg/Ca-ratios of Arctic benthic foraminifera and the ambient bottom water temperatures (BWT). The area is influenced by large seasonal variation in factors such as light and temperature, which is further strengthened by oceanographic shifts, ...
    • Biocryomorphology: integrating microbial processes with ice surface hydrology, topography and roughness 

      Cook, J.; Edwards, A.; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-02)
    • Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea 

      Lee, Dong-Hun; Kim, Jung-Hyun; Lee, Yung Mi; Stadnitskaia, Alina; Jin, Young Keun; Niemann, Helge; Kim, Young-Gyun; Shin, Kyung-Hoon (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-20)
      In this study, we report lipid biomarker patterns and phylogenetic identities of key microbial communities mediating anaerobic oxidation of methane (AOM) in active mud volcanoes (MVs) on the continental slope of the Canadian Beaufort Sea. The carbon isotopic compositions (δ13C) of sn-2- and sn-3-hydroxyarchaeol showed the highly 13C-depleted values (−114 ‰ to −82 ‰) associated with a steep depletion ...
    • Bivalve shell horizons in seafloor pockmarks of the last glacial-interglacial transition suggest a thousand years of methane emissions in the Arctic Ocean 

      Ambrose, William; Panieri, Giuliana; Schneider, Andrea; Plaza-Faverola, Andreia; Carroll, Michael Leslie; Åström, Emmelie; Locke, W.L.; Carroll, JoLynn (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-05)
      We studied discrete bivalve shell horizons in two gravity cores from seafloor pockmarks on the Vestnesa Ridge (1200 m water depth) and western Svalbard (798000 N, 068550 W) to provide insight into the temporal and spatial dynamics of seabed methane seeps. The shell beds, dominated by two genera of the family Vesicomyidae: Phreagena s.l. and Isorropodon sp., were 20–30 cm thick and centered at ...
    • Bottom water acidification and warming on the western Eurasian Arctic shelves: Dynamical downscaling projections 

      Wallhead, P. J.; Bellerby, R.G.J.; Silyakova, A.; Slagstad, D.; Polukhin, A. A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-25)
      The impacts of oceanic CO2 uptake and global warming on the surface ocean environment have received substantial attention, but few studies have focused on shelf bottom water, despite its importance as habitat for benthic organisms and demersal fisheries such as cod. We used a downscaling ocean biogeochemical model to project bottom water acidification and warming on the western Eurasian Arctic ...