Now showing items 641-660 of 729

    • Episodic release of CO2 from the high-latitude North Atlantic Ocean during the last 135 kyrs 

      Ezat, Mohamed; Rasmussen, Tine Lander; Honisch, Barbel; Groeneveld, Jeroen; DeMenocal, P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-22)
      Antarctic ice cores document glacial-interglacial and millennial-scale variability in atmospheric pCO2 over the past 800 kyr. The ocean, as the largest active carbon reservoir on this timescale, is thought to have played a dominant role in these pCO2 fluctuations, but it remains unclear how and where in the ocean CO2 was stored during glaciations and released during (de)glacial millennial-scale ...
    • Some giant submarine landslides do not produce large tsunamis 

      Løvholt, Finn; Bondevik, Stein; Laberg, Jan Sverre; Kim, Jihwan; Boylan, Noel (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-07)
      Landslides are the second-most important cause of tsunamis after earthquakes, and their potential for generating large tsunamis depend on the slide process. Among the world's largest submarine landslides is the Storegga Slide that generated an ocean-wide catastrophic tsunami, while no traces of a tsunami generated from the similar and nearby Trænadjupet Slide have been found. Previous models for ...
    • Removal of methane through hydrological, microbial, and geochemical processes in the shallow sediments of pockmarks along eastern Vestnesa Ridge (Svalbard) 

      Hong, Wei-Li; Sauer, Simone; Panieri, Giuliana; Ambrose, William; James, Rachel; Plaza-Faverola, Andreia; Schneider, Andrea (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      The recent discovery of methane seeps in the Arctic region requires a better understanding of the fate of methane in marine sediments if we are to understand the contributions of methane to Arctic ecosystems and climate change. To further this goal, we analyze pore water data from five pockmarks along eastern Vestnesa Ridge, a sediment drift northwest of Svalbard, to quantify the consumption ...
    • Sources and turnover of organic carbon and methane in fjord and shelf sediments off Northern Norway 

      Sauer, Simone; Hong, Wei-Li; Knies, Jochen; Lepland, Aivo; Forwick, Matthias; Klug, Martin; Eichinger, Florian; Baranwal, Soma; Cremiere, Antoine; Chand, Shyam; Schubert, Carsten J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-22)
      To better understand the present and past carbon cycling and transformation processes in methane-influenced fjord and shelf areas of northern Norway, we compared two sediment cores from the Hola trough and from Ullsfjorden. We investigated (1) the organic matter composition and sedimentological characteristics to study the sources of organic carbon (C<sub>org</sub>) and the factors influencing ...
    • Paleo-methane emissions recorded in foraminifera near the landward limit of the gas hydrate stability zone offshore western Svalbard 

      Panieri, Giuliana; Graves, Carolyn; James, Rachel (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-26)
      We present stable isotope and geochemical data from four sediment cores from west of Prins Karls Forland (ca. 340 m water depth), offshore western Svalbard, recovered from close to sites of active methane seepage, as well as from shallower water depths where methane seepage is not presently observed. Our analyses provide insight into the record of methane seepage in an area where ongoing ocean ...
    • A late-Holocene multi-proxy record from the northern Norwegian margin: Temperature and salinity variability 

      Berben, Sarah Miche Patricia; Husum, Katrine; Sørensen, Steffen Aagaard (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-01)
      To elucidate the natural variability of Atlantic and Coastal water, a late-Holocene multi-proxy analysis is performed on a marine sediment core from the northern Norwegian margin. This includes planktic foraminiferal fauna and their preservation indicators, stable isotopes (δ18Oc, δ13C), sub-surface temperature (SSTMg/Ca) and salinity (SSS) records based on paired Mg/Ca and δ18Oc measurements of ...
    • 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 ...
    • Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data 

      Singhroha, Sunny; Bünz, Stefan; Plaza-Faverola, Andreia; Chand, Shyam (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-23)
      We have estimated the seismic attenuation in gas hydrate and free-gas-bearing sediments from high-resolution P-cable 3D seismic data from the Vestnesa Ridge on the Arctic continental margin of Svalbard. P-cable data have a broad bandwidth (20–300 Hz), which is extremely advantageous in estimating seismic attenuation in a medium. The seismic quality factor (Q), the inverse of seismic attenuation, ...
    • Submarginal drumlin formation and late Holocene history of Fláajökull, southeast Iceland 

      Jónsson, Sverrir A.; Benediktsson, Ívar Örn; Ingólfsson, Ólafur; Schomacker, Anders; Bergsdóttir, Helga Lucia; Jacobson Jr., William R.; Linderson, Hans (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Fláajökull is a non-surging outlet glacier draining the south-eastern part of the Vatnajökull, southeast Iceland. Fláajökull was stationary or advanced slightly between 1966 and 1995 and formed a prominent end moraine. Glacial retreat since then has revealed a cluster of 15 drumlins. This study focuses on the morphology and sedimentology of the drumlins. They are 100–600 m long, 40–130 m wide, and ...
    • Production of fluorescent dissolved organic matter in Arctic Ocean sediments 

      Chen, Meilian; Kim, Ji-Hoon; Nam, Seung-Il; Niessen, Frank; Hong, Wei-Li; Kang, Moo-Hee; Hur, Jin (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the ...
    • 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 ...
    • Freshwater ostracods (Crustacea) and environmental variability of polygon ponds in the tundra of the Indigirka Lowland, north-east Siberia 

      Schneider, Andrea; Wetterich, Sebastian; Schirrmeister, Lutz; Herzschuh, Ulrike; Meyer, Hanno; Pestryakova, Luidmila A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Freshwater ostracods (Crustacea, Ostracoda) are valuable biological indicators. In Arctic environments, their habitat conditions are barely known and the abundance and diversity of ostracods is documented only in scattered records with incomplete ecological characterization. To determine the taxonomic range of ostracod assemblages and their habitat conditions in polygon ponds in the Indigirka Lowland, ...
    • Depositional environment, ichnological features and oxygenation of Permian to earliest Triassic marine sediments in central Spitsbergen, Svalbard 

      Uchman, Alfred; Hanken, Nils-Martin; Nielsen, Jesper Kresten; Grundvåg, Sten-Andreas; Piasecki, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Late Early Permian–lowermost Triassic carbonate, siliceous (spiculites) and clastic marine sediments in the Marmierfjellet area (Isfjorden, central Spitsbergen) contain a relatively diverse and abundant trace fossil assemblage providing important information about the depositional processes. The Vøringen Member (Late Artinskian–Kungurian) of the Kapp Starostin Formation (Late Artinskian–? Changhsingian) ...
    • Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet 

      Cremiere, Antoine; Lepland, Aivo; Chand, Shyam; Sahy, Diana; Condon, Daniel J.; Noble, Stephen R.; Martma, Tõnu; Thorsnes, Terje; Sauer, Simone; Brunstad, Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-11)
      Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents ...
    • Two-stage exhumation of subducted Saxothuringian continental crust records underplating in the subduction channel and collisional forced folding (Krkonoše-Jizera Mts., Bohemian Massif) 

      Jerabek, Petr; Konopasek, Jiri; Žáčková, Eliška (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08)
      The Krkonoše-Jizera Massif in the northern part of the Variscan Bohemian Massif provides insight into the exhumation mechanisms for subducted continental crust. The studied region exposes a relatively large portion of a flat-lying subduction-related complex that extends approximately 50 km away from the paleosuture. wide extent of HP-LT metamorphism has been confirmed by new P-T estimates indicating ...
    • 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 ...
    • Evidence for ice-free summers in the late Miocene central Arctic Ocean 

      Stein, Ruediger; Fahl, Kirsten; Schreck, Michael; Knorr, Gregor; Niessen, Frank; Forwick, Matthias; Gebhardt, Catalina; Jensen, Laura; Kaminski, Michael; Kopf, Achim; Matthiessen, Jens; Jokat, Wilfried; Lohmann, Gerrit (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-04)
      Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earth’s climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger ...
    • Deconvoluting complex structural histories archived in brittle fault zones 

      Viola, Giulio; Scheiber, Thomas; Fredin, Ola; Zwingmann, Horst; Margreth, A (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-16)
      Brittle deformation can saturate the Earth’s crust with faults and fractures in an apparently chaotic fashion. The details of brittle deformational histories and implications on, for example, seismotectonics and landscape, can thus be difficult to untangle. Fortunately, brittle faults archive subtle details of the stress and physical/chemical conditions at the time of initial strain localization ...
    • Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling 

      Pisso, Ignacio; Myhre, Cathrine Lund; Platt, Stephen Matthew; Eckhardt, Sabine; Hermansen, Ove; Schmidbauer, Josef Norbert; Mienert, Jurgen; Vadakkepuliyambatta, Sunil; Bauguitte, S.; Pitt, J; Allen, G.; Bower, KN; O'Shea, S; Gallagher, MW; Percival, C.J; Pyle, J; Cain, M.; Stohl, Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-10)
    • Long-lasting Cadomian magmatic activity along an active northern Gondwana margin: U–Pb zircon and Sr–Nd isotopic evidence from the Brunovistulian Domain, eastern Bohemian Massif 

      Soejono, Igor; Janoušek, Vojtěch; Žáčková, Eliška; Slama, Jiri; Konopasek, Jiri; Machek, Matěj; Hanžl, Pavel (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-03)
      Cadomian magmatic complexes of the Brunovistulian Domain crop out at the eastern termination of the Bohemian Massif. However, the age, nature and geotectonic affinity of some of pre-Variscan (meta-)igneous rock complexes from this domain are still unknown. Geochronological and geochemical study of the granitic rocks across the Brunovistulian Domain reveals new information about the timing and nature ...