Viser treff 150-169 av 711

    • Does Arctic warming reduce preservation of organic matter in Barents Sea sediments? 

      Faust, Johan Christoph; Stevenson, Mark A.; Abbott, Geoffrey D.; Knies, Jochen; Tessin, Allyson; Mannion, Isobel; Ford, Ailbe; Hilton, Robert; Peakall, Jeffrey; März, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-31)
      Over the last few decades, the Barents Sea experienced substantial warming, an expansion of relatively warm Atlantic water and a reduction in sea ice cover. This environmental change forces the entire Barents Sea ecosystem to adapt and restructure and therefore changes in pelagic–benthic coupling, organic matter sedimentation and long-term carbon sequestration are expected. Here we combine new and ...
    • Dry and strong quartz during deformation of the lower crust in the presence of melt 

      Menegon, Luca; Nasipuri, Pritam; Stunitz, Holger; Behrens, Harald; Ravna, Erling J Krogh (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Granulite facies migmatitic gneisses from the Seiland Igneous Province (northern Norway) were deformed during deep crustal shearing in the presence of melt, which formed by dehydration melting of biotite. Partial melting and deformation occurred during the intrusion of large gabbroic plutons at the base of the lower crust at 570 to 520 Ma in an intracontinental rift setting. The migmatitic gneisses ...
    • Dynamic and history of methane seepage in the SW Barents Sea: new insights from Leirdjupet Fault Complex 

      Argentino, Claudio; Waghorn, Kate Alyse; Vadakkepuliyambatta, Sunil; Polteau, Stephane; Bünz, Stefan; Panieri, Giuliana (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-23)
      Methane emissions from Arctic continental margins are increasing due to the negative effect of global warming on ice sheet and permafrost stability, but dynamics and timescales of seafloor seepage still remain poorly constrained. Here, we examine sediment cores collected from an active seepage area located between 295 and 353 m water depth in the SW Barents Sea, at Leirdjupet Fault Complex. The ...
    • Dynamics of a retreating ice sheet: a LiDAR study in Värmland, SW Sweden 

      Goodship, Alastair; Alexanderson, Helena (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-11)
      Värmland in south western Sweden lies across the established zone of marine-terrestrial transition of the Scandinavian Ice Sheet (SIS) margin. The region lies inside the Younger Dryas maximum limit reached at 12.7 cal ka BP and the area of rapid final SIS retreat from 11.5 cal ka BP. LiDAR data across Värmland allows more detailed observation and analysis of glacial landforms formed during this stage ...
    • Early and middle Miocene ice sheet dynamics in the Ross Sea: Results from integrated core-log-seismic interpretation 

      Perez, Lara F; De Santis, Laura; Mckay, Robert M.; Larter, Robert D.; Ash, Jeanine A; Bart, Phil J.; Böhm, Gualtiero; Brancatelli, Giuseppe; Browne, Imogen; Colleoni, Florence; Dodd, Justin P.; Geletti, Riccardo; Harwood, David M.; Kuhn, Gerhard; Laberg, Jan Sverre; Leckie, R. Mark; Levy, Richard H.; Marschalek, James; Mateo, Zenon; Naish, Timothy R.; Sangiorgi, Francesca; Shevenell, Amelia E.; Sorlien, Christopher C.; van de Flierdt, Tina; IODP Expedition 374, Scientists (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-11)
      Oscillations in ice sheet extent during early and middle Miocene are intermittently preserved in the sedimentary record from the Antarctic continental shelf, with widespread erosion occurring during major ice sheet advances, and open marine deposition during times of ice sheet retreat. Data from seismic reflection surveys and drill sites from Deep Sea Drilling Project Leg 28 and International Ocean ...
    • Early and Middle Pleistocene environments, landforms and sediments in Scotland 

      Hall, Adrian M.; Merritt, Jon W.; Connell, E. Rodger; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-04)
      This paper reviews the changing environments, developing landforms and terrestrial stratigraphy during the Early and Middle Pleistocene stages in Scotland. Cold stages after 2.7 Ma brought mountain ice caps and lowland permafrost, but larger ice sheets were short-lived. The late Early and Middle Pleistocene sedimentary record found offshore indicates more than 10 advances of ice sheets from ...
    • An Early Neogene—Early Quaternary Contourite Drift System on the SW Barents Sea Continental Margin, Norwegian Arctic 

      Rydningen, Tom Arne; Høgseth, Gert; Lasabuda, Amando Putra Ersaid; Laberg, Jan Sverre; Safronova, Polina; Forwick, Matthias (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-30)
      The onset and evolution of the middle to late Cenozoic “icehouse” world was influenced by the development of the global ocean circulation linking the Norwegian–Greenland Sea-Arctic Ocean to the Atlantic Ocean. The evolution of the early Neogene to early Quaternary Bjørnøyrenna Drift, located at the SW Barents Sea continental margin, shed new light on this important hydrological event. By analyzing ...
    • The Early to Middle Cenozoic Paleoenvironment and Erosion Estimates for the northwestern Barents Sea 

      Lasabuda, Amando Putra Ersaid; Laberg, Jan Sverre; Knutsen, Stig-Morten; Safronova, Polina (Conference object; Konferansebidrag, 2017)
      <p>The northwestern Barents Sea continental margin is a structurally complex area characterized by a series of basins and highs. It’s Cenozoic development was influenced by: 1) the formation of the Spitsbergen fold-andthrust belt towards the north and a pull-apart basin, the Vestbakken Volcanic Province, to the south, and 2) the subsequent rifting and opening of the Fram Strait, the deep-water gateway ...
    • Early to middle Cenozoic paleoenvironment and erosion estimates of the southwestern Barents Sea: Insights from a regional mass-balance approach 

      Lasabuda, Amando Putra Ersaid; Laberg, Jan Sverre; Knutsen, Stig-Morten; Høgseth, Gert (Journal article; Tidsskriftartikkel, 2018-06-02)
      The Cenozoic pre-glacial development of the southwestern Barents Sea is discussed, with focus on the early to middle Cenozoic net erosion that was poorly constrained. From 2D and 3D seismic mapping, the western Barents Sea continental margin development shows a complex history of structural configuration of highs and basins related to the Greenland and Eurasian plate movement and subsequent seafloor ...
    • The effect of an experimental decrease in salinity on the viability of the subarctic planktonic foraminifera Neogloboquadrina incompta 

      Greco, Mattia; Meilland, Julie; Zamelczyk, Kasia; Rasmussen, Tine Lander; Kucera, Michal (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-27)
      Chemical signatures in the calcite of shells of polar and subpolar planktonic foraminifera have been frequently used to trace and quantify past meltwater discharge events. This approach assumes that the foraminifera can tolerate low salinity under extended periods. To obtain a first experimental constraint on salinity tolerance of Subarctic foraminifera, we carried out a culturing experiment with ...
    • The effect of Dauphiné twinning on plastic strain in quartz 

      Menegon, Luca; Piazolo, Sandra; Pennacchioni, Giorgio (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      We present an electron backscatter diffraction analysis of five quartz porphyroclasts in a greenschist facies (T = 300–400°C) granitoid protomylonite from the Arolla unit of the NW Alps. Mechanical Dauphiné twinning developed pervasively during the incipient stage of deformation within two porphyroclasts oriented with a negative rhomb plane {z} almost orthogonal to the compression direction (z-twin ...
    • The effect of muscovite on the microstructural evolution and rheology of quartzite in general shear 

      Tokle, L.; Hirth, G.; Stunitz, Holger (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-13)
      We conducted general shear experiments on synthetic mixtures of quartz and muscovite aggregates at 800 °C and 1.5 GPa with 0.1 wt% H<sub>2</sub>O added in the Griggs apparatus to investigate the role of muscovite content on the microstructural evolution and rheological properties of quartz aggregates. Muscovite content varied between 0, 5, 10 and 25% muscovite. Mechanically, the sample strengths ...
    • Effect of pressure on the deformation of quartz aggregates in the presence of H2O 

      Nègre, Lucille; Stunitz, Holger; Raimbourg, Hugues; Lee, Amicia; Précigout, Jacques; Pongrac, Petar; Jeřábek, Petr (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-17)
      Quartzite samples of high purity with a grain size of ~200 μm have been experimentally deformed by coaxial shortening in a solid medium apparatus at 900 °C and at confining pressures ranging from 0.6 to 2 GPa. Most samples have been shortened by ~30% with 0.1 wt% added H<sub>2</sub>O. The samples deformed dominantly by crystal plasticity (dislocation creep), and there is a systematic decrease of ...
    • Effectiveness of Fluorescent Viability Assays in Studies of Arctic Cold Seep Foraminifera 

      Melaniuk, Katarzyna (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-09)
      Highly negative δ<sup>13</sup>C values in fossil foraminifera from methane cold seeps have been proposed to reflect episodes of methane release from gas hydrate dissociation or free gas reservoirs triggered by climatic changes in the past. Because most studies on live foraminifera are based on the presence of Rose Bengal staining, that colors the cytoplasm of both live and recently dead individuals ...
    • Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean: A review 

      James, Rachel; Bousquet, Philippe; Bussmann, Ingeborg; Haeckel, Matthias; Kipfer, Rolf; Leifer, Ira; Niemann, Helge; Ostrovsky, Ilia; Piskozub, Jacek; Rehder, Gregor; Treude, Tina; Vielstadte, Lisa; Greinert, Jens (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-17)
      Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the seabed, the fate of this methane in the water column, ...
    • Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters 

      Steinle, Lea; Maltby, Johanna; Treude, Tina; Kock, Annette; Bange, Hermann W.; Engbersen, Nadine; Zopfi, Jakob; Lehmann, Moritz F.; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-29)
      Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from which it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter, reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially ...
    • Effects of mortality changes on biomass and production in Calanus spp. populations 

      Skardhamar, Jofrid; Reigstad, Marit; Carroll, Jolynn; Eiane, Ketil; Wexels Riser, Christian; Slagstad, Dag (Journal article; Tidsskriftartikkel; Peer reviewed, 2011-04-28)
      Calanus species are the main link between primary producers and higher trophic-level organisms in the Barents Sea. The natural mortality rate is an essential parameter for determining the standing stock of Calanus, but it is also one of the most uncertain parameters in present knowledge. The level of human activity, and the associated risk of pollution, is increasing in the Barents Sea, and knowledge ...
    • EISCAT Observation of Wave‐Like Fluctuations in Vertical Velocity of Polar Mesospheric Summer Echoes Associated With a Geomagnetic Disturbance 

      Lee, Young-Sook; Kim, Young Ha; Kim, Kyung-Chan; Kwak, Young-Sil; Sergiengko, Timothy; Kirkwood, Sheila; Johnsen, Magnar Gullikstad (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-06-04)
      By analyzing a data set from the European Incoherent SCATter (EISCAT) Very High Frequency (VHF) radar at Tromsø, we find that both radar reflectivity and upward ion velocity in a polar mesospheric summer echo (PMSE) layer simultaneously increased at the commencement of a local geomagnetic disturbance, which occurred at midnight on 9 July 2013. The onset of the upward velocity was followed by periodic ...
    • Elevated methane alters dissolved organic matter composition in the Arctic Ocean cold seeps 

      Sert, Muhammed Fatih; Schweitzer, Hannah; de Groot, Tim R.; Kekäläinen, Timo; Jänis, Janne; Bernstein, Hans Christopher; Ferré, Benedicte; Gründger, Friederike; Kalenitchenko, Dimitri Stanislas Desire; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-15)
      Cold seeps release methane (CH<sub>4</sub>) from the seafloor to the water column, which fuels microbially mediated aerobic methane oxidation (MOx). Methane-oxidising bacteria (MOB) utilise excess methane, and the MOB biomass serves as a carbon source in the food web. Yet, it remains unclear if and how MOx modifies the composition of dissolved organic matter (DOM) in cold seeps. We investigated MOx ...
    • Elevation changes of the Fennoscandian Ice Sheet interior during the last deglaciation 

      Lane, T.P.; Paasche, Øyvind; Kvisvik, B.; Adamson, K.R.; Rodés, Á.; Patton, Henry; Gomez, N.; Gheorghiu, D.; Bakke, J.; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-20)
      The dynamics of ice sheet interiors during the last deglaciation are poorly constrained, hindering evaluation of ice sheet models. We provide direct evidence of Fennoscandian Ice Sheet (FIS) interior behaviour during deglaciation through surface exposure dating. Our results demonstrate early thinning of the FIS, prior to the Younger Dryas (YD, 12.8‐11.7 ka). Interior thinning in central Norway was ...