Now showing items 581-600 of 729

    • Semi-quantitative reconstruction of early to late Holocene spring and summer sea ice conditions in the northern Barents Sea 

      Berben, Sarah Miche Patricia; Husum, Katrine; Navarro-Rodriguez, Alba; Belt, Simon T.; Sørensen, Steffen Aagaard (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-07)
      Semi-quantitative estimates of early to late Holocene spring sea ice concentration (SpSIC) andoccurrence of summer sea ice for the northern Barents Sea have been obtained by analysing the biomarkers IP<sub>25</sub>,brassicasterol and a tri-unsaturated highly branched isoprenoid lipid in a Holocene marine sediment core.Sub-surface water mass variations were derived from planktic foraminiferal assemblages ...
    • Water redistribution in experimentally deformed natural milky quartz single crystals?Implications for H2O-weakening processes 

      Stünitz, H.; Thust, A.; Heilbronner, R.; Behrens, H.; Kilian, R.; Tarantola, A.; Fitz Gerald, J.D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-22)
      Natural quartz single crystals were experimentally deformed in two orientations: (1) ⊥ to one prism plane and (2) in O+ orientation at 900 and 1000°C, 1.0 and 1.5 GPa, and strain rates of ~1 × 10−6 s−1. In addition, hydrostatic and annealing experiments were performed. The starting material was milky quartz, which consisted of dry quartz with a large number of fluid inclusions of variable size up ...
    • Microseismicity linked to gas migration and leakage on the western Svalbard shelf 

      Franek, Peter; Plaza-Faverola, Andreia; Mienert, Jurgen; Bünz, Stefan; Ferré, Benedicte; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-26)
      The continental margin off Prins Karls Forland, western Svalbard, is characterized by widespread natural gas seepage into the water column at and upslope of the gas hydrate stability zone. We deployed an ocean bottom seismometer integrated into the MASOX (Monitoring Arctic Seafloor-Ocean Exchange) automated seabed observatory at the pinch-out of this zone at 389 m water depth to investigate passive ...
    • A flexural isostasy model for the Pleistocene evolution of the Barents Sea bathymetry 

      Zieba, Krzysztof Jan; Omosanya, Kamaldeen Olakunle; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-24)
      The topographic relief of the Barents Sea was subjected to major changes during the past 1.5 million years mostly due to sediment redistribution driven by glacial activity. This paper addresses the problem of Pleistocene bathymetric evolution of the southern Barents Sea using a numerical modelling approach that considers the influence of regional isostasy on relief development. The model presented ...
    • U-Th chronology and formation controls of methane-derived authigenic carbonates from the Hola trough seep area, northern Norway 

      Sauer, Simone; Knies, Jochen; Lepland, Aivo; Sahy, Diana; Martma, Tõnu; Noble, Stephen R.; Schönenbergerb, Jasmin; Klug, Martin; Schubert, Carsten J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-20)
      We investigated methane-derived authigenic carbonate (MDAC) crusts and nodules from a cold seep site on the northern Norwegian continental shelf in ca. 220 m water depth to determine the timing and mode of their formation. Gas bubbling observed during remotely operated vehicle (ROV)-assisted sampling of MDAC crusts revealed ongoing seep activity. Authigenic carbonates were present as crusts on the ...
    • Postglacial response of Arctic Ocean gas hydrates to climatic amelioration 

      Serov, Pavel; Vadakkepuliyambatta, Sunil; Mienert, Jurgen; Patton, Henry; Portnov, Aleksei D; Silyakova, Anna; Panieri, Giuliana; Carroll, Michael Leslie; Carroll, JoLynn; Andreassen, Karin; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-05)
      Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate ...
    • Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal 14C dates 

      Mohamed, Ezat M.; Rasmussen, Tine L.; Thornalley, David J.R.; Olsen, Jesper; Skinner, Luke C.; Hönisch, Bärbel; Groeneveld, Jeroen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-10)
      Formation of deep water in the high‐latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water‐column radiocarbon age reconstructions in the Faroe‐Shetland Channel, southeastern Norwegian ...
    • Relationship between mega-scale glacial lineations and iceberg ploughmarks on the Bjørnøyrenna Palaeo-Ice Stream bed, Barents Sea 

      Andreassen, Karin; Piasecka, Emilia D.; Stokes, Chris R.; Winsborrow, Monica C.M. (Journal article; Tidsskriftartikkel, 2018-02-24)
      Mega-scale glacial lineations (MSGLs) are ridge-groove corrugations aligned in the direction of the former ice flow, tens of kilometers long and up to a few hundred meters wide. They are the most striking subglacial features on the beds of former ice streams and play an important role in modulating ice flow through their influence on bed roughness and subglacial hydrology. Despite the importance of ...
    • Shallow methane hydrate system controls ongoing, downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand 

      Mountjoy, J.J.; Pecher, Ingo; Henrys, Stuart; Crutchley, Gareth; Barnes, P.M.; Plaza-Faverola, Andreia (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-10-14)
    • Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate-charged Vestnesa Ridge, Svalbard 

      Smith, Andrew James; Mienert, Jurgen; Bünz, Stefan; Greinert, Jens (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-04-21)
      We use new gas‐hydrate geochemistry analyses, echosounder data, and three‐dimensional P‐Cable seismic data to study a gas‐hydrate and free‐gas system in 1200 m water depth at the Vestnesa Ridge offshore NW Svalbard. Geochemical measurements of gas from hydrates collected at the ridge revealed a thermogenic source. The presence of thermogenic gas and temperatures of ∼3.3°C result in a shallow top of ...
    • Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane 

      Pohlman, John; Greinert, Jens; Ruppel, Carolyn; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-08)
      Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global ...
    • Geochemical characterisation of northern Norwegian fjord surface sediments: A baseline for further paleo-environmental investigations 

      Faust, Johan Christoph; Scheiber, Thomas; Fabian, Karl; Vogt, Christoph; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-26)
      Norwegian fjord sediments are promising archives for very high resolution records of past environmental changes. Recent investigations of the modern depositional environment within fjords revealed that the accurate quantification of the inputs, sources, and sedimentary preservation of organic and inorganic material is crucial to decipher long term past climate signals in the sedimentary record ...
    • Identifying past petroleum exploration related drill cutting releases and influences on the marine environment and benthic foraminiferal communities, Goliat Field, SW Barents Sea, Norway 

      Sørensen, Steffen Aagaard; Junttila, Juho; Dijkstra, Noortje (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-01)
      The present multiproxy investigation of marine sediment cores aims at: 1) Identifying dispersion of petroleum exploration related drill cutting releases within the Goliat Field, Barents Sea in 2006/07 and 2) Assessing past and present influence of drill cuttings on the marine environment. The cores were recovered 5, 30, 60, 125 and 250 m from the drill site in the eastward downstream direction.<p> ...
    • CO2 flux over young and snow-covered Arctic pack ice in winter and spring 

      Nomura, Daiki; Granskog, Mats A.; Fransson, Agneta; Chierici, Melissa; Silyakova, Anna; Ohshima, Kay; Cohen, Lana; Delille, Bruno; Hudson, Stephen R.; Dieckmann, Gerhard (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-05)
      Rare CO2 flux measurements from Arctic pack ice show that two types of ice contribute to the release of CO2 from the ice to the atmosphere during winter and spring: young, thin ice with a thin layer of snow and older (several weeks), thicker ice with thick snow cover. Young, thin sea ice is characterized by high salinity and high porosity, and snow-covered thick ice remains relatively warm ( >  −7.5 °C) ...
    • Formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern Norway 

      Laberg, Jan Sverre; Baeten, Nicole Jeanne; Lågstad, Petter Arthur; Forwick, Matthias; Vorren, Tore Ola (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-08-30)
      High-resolution swath-bathymetry data integrated with sub-bottom profiles and single-channel seismics reveal an 18 km long, up to 1000 m wide and 10-15 m deep crack located approx. 4 km upslope from a slide scar on the continental slope off northern Norway. This crack is formed by subsidence of the sea-floor sediments to a depth of 120 m due to downslope movement of a ~80 km2 large sediment slab ...
    • Reconstructing the retreat dynamics of the Bjørnøyrenna Ice Stream based on new 3D seismic data from the central Barents Sea 

      Piasecka, Emilia Daria; Winsborrow, Monica; Andreassen, Karin; Stokes, Chris R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-01)
      The stability of contemporary ice sheets is influenced by the discharge from ice streams - corridors of fast-flowing ice bounded by ice flowing an order of magnitude slower. Reconstructions of palaeo-ice stream dynamics contribute to our understanding of ice stream sensitivity to the ocean-climate system and can aid in the numerical modelling and prediction of future changes in contemporary ice ...
    • Glacial isostatic adjustment associated with the Barents Sea ice sheet: A modelling inter-comparison 

      Auriac, Amandine; Whitehouse, P.L.; Bentley, M.J.; Patton, Henry; Lloyd, J.M.; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-01)
      The 3D geometrical evolution of the Barents Sea Ice Sheet (BSIS), particularly during its late-glacial retreat phase, remains largely ambiguous due to the paucity of direct marine- and terrestrial-based evidence constraining its horizontal and vertical extent and chronology. One way of validating the numerous BSIS reconstructions previously proposed is to collate and apply them under a wide range ...
    • Complementary biomarker-based methods for characterising Arctic sea ice conditions: A case study comparison between multivariate analysis and the PIP25 index 

      Koseoglu, Denizcan; Belt, Simon T.; Smik, Lukas; Yao, Haoyi; Panieri, Giuliana; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-10)
      The discovery of IP25 as a qualitative biomarker proxy for Arctic sea ice and subsequent introduction of the so-called PIP25 index for semi-quantitative descriptions of sea ice conditions has significantly advanced our understanding of long-term paleo Arctic sea ice conditions over the past decade. We investigated the potential for classification tree1 (CT) models to provide a further approach ...
    • 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 ...
    • A new genus and two new species of Thyasiridae associated with methane seeps off Svalbard, Arctic Ocean 

      Åström, Emmelie; Oliver, Graham; Carroll, Michael Leslie (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-16)
      Bivalves have been found in unique benthic assemblages associated with active methane seeps and mounds along the western and southern margins of the Svalbard shelf (75–79°N) at 350–380 m depth. Among the samples collected were a number of shells of Thyasiridae that are distinct from any species previously described. Here we describe one new genus Rhacothyas gen. nov. and two new species Thyasira ...