Viser treff 677-696 av 698

    • Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene 

      Wegner, C.; Bennet, K.; Vernal, Anne de; Forwick, Matthias; Fritz, M.; Heikkilä, Maija; Łącka, Magdalena; Lantuit, Hugues; Laska, Michał; Moskalik, Mateusz; O’Regan, Matt; Pawłowska, J; Promińska, Agnieszka; Rachold, Volker; Vonk, Jorien E.; Werner, Kirstin (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-09)
      Arctic coastal zones serve as a sensitive filter for terrigenous matter input onto the shelves via river discharge and coastal erosion. This material is further distributed across the Arctic by ocean currents and sea ice. The coastal regions are particularly vulnerable to changes related to recent climate change. We compiled a pan-Arctic review that looks into the changing Holocene sources, transport ...
    • Variability of Acoustically Evidenced Methane Bubble Emissions Offshore Western Svalbard 

      Veloso-Alarcon, Mario E.; Jansson, Pär; De Batist, Marc; Minshull, Timothy A.; Westbrook, Graham K.; Pälike, Heiko; Bünz, Stefan; Wright, Ian; Greinert, Jens (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-22)
      Large reservoirs of methane present in Arctic marine sediments are susceptible to rapid warming, promoting increasing methane emissions. Gas bubbles in the water column can be detected, and flow rates can be quantified using hydroacoustic survey methods, making it possible to monitor spatiotemporal variability. We present methane (CH<sub>4</sub>) bubble flow rates derived from hydroacoustic data ...
    • Variability of Marine Methane Bubble Emissions on the Clayoquot Slope, Offshore Vancouver Island, Between 2017 and 2021 

      Marcon, Yann; Römer, Miriam; Scherwath, Martin; Riedel, Michael; Dølven, Knut Ola; Heesemann, Martin (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-17)
      Seabed methane gas emissions occur worldwide at cold seeps located along most continental margins. Fluxes of methane gas released from the seabed in the form of bubbles can be extremely variable even over short time intervals. Some factors controlling the variability are still poorly understood. Here, we report on the results of continuous long-term sonar monitoring of bubble emissions at a depth ...
    • Variability of present and past PAH concentrations in sediments of the SW Barents Sea 

      Junttila, Juho; Carroll, JoLynn; Dijkstra, Noortje (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-10-09)
      The concentration and distribution of polyaromatic hydrocarbons (PAHs) in surface and subsurface sediment samples from Tromsøflaket and Ingøydjupet, southwestern Barents Sea, were investigated in order to provide insight into the levels and origins of PAHs in a region with petroleum activities. PAH profiles in sediments were evaluated in context with sediment grain size and total organic carbon ...
    • Variations in benthic foraminiferal assemblages in the Tagus mud belt during the last 5700 years: Implications for Tagus River discharge 

      Dessandier, Pierre-Antoine; Bonnin, Jérôme; Malaizé, Bruno; Lambert, Clément; Tjallingii, Rik; Warden, Lisa; Sinninghe Damsté, Jaap S.; Kim, Jung-Hyun (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-31)
      We analyzed a 10-m sediment core retrieved at 82 m water depth off the coast of the Tagus River (Western Iberian Margin, Portugal) to investigate a linkage between variations in benthic foraminiferal assemblages and Tagus River discharge over the last 5700 years. Benthic foraminiferal assemblages were studied at high resolution in combination with the stable carbon and oxygen isotopic composition ...
    • Variations in gas and water pulses at an Arctic seep: fluid sources and methane transport 

      Hong, Wei-Li; Torres, Marta E.; Portnov, Aleksei D; Waage, Malin; Haley, B.; Lepland, Aivo (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-19)
      Methane fluxes into the oceans are largely dependent on the methane phase as it migrates upward through the sediments. Here we document decoupled methane transport by gaseous and aqueous phases in Storfjordrenna (offshore Svalbard) and propose a three‐stage evolution model for active seepage in the region where gas hydrates are present in the shallow subsurface. In a preactive seepage stage, solute ...
    • Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data 

      Goswami, Bedanta K.; Weitemeyer, Karen A.; Bünz, Stefan; Minshull, Timothy A.; Westbrook, Graham K.; Ker, Stephan; Sinha, Martin C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-10)
      The Vestnesa Ridge marks the northern boundary of a known submarine gas hydrate province in the west Svalbard margin. Several seafloor pockmarks at the eastern segment of the ridge are sites of active methane venting. Until recently, seismic reflection data were the main tool for imaging beneath the ridge. Coincident controlled source electromagnetic (CSEM), high‐resolution two‐dimensional (2‐D) ...
    • 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 ...
    • Visualizing and interpreting surface displacement patterns on unstable slopes using multi-geometry satellite SAR interferometry (2D InSAR) 

      Eriksen, Harald Øverli; Lauknes, Tom Rune; Larsen, Yngvar; Corner, Geoffrey D.; Bergh, Steffen G; Dehls, John; Kierulf, Halfdan Pascal (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-05)
      It is well known that satellite radar interferometry (InSAR) is capable of measuring surface displacement with a typical accuracy on the order of millimeters to centimeters. However, when the true deformation vector differs from the satellite line-of-sight (LOS), the sensitivity decreases and interpretation of InSAR deformationmeasurements becomes challenging. By combining displacement data ...
    • Visualizing tephra deposits and sedimentary processes in the marine environment: The potential of X-ray microtomography 

      Griggs, Adam J.; Davies, Siwan M.; Abbott, Peter M.; Coleman, Mark; Palmer, Adrian P.; Rasmussen, Tine Lander; Johnston, Richard (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-30)
      Localized tephra deposition in marine sequences is the product of many complex primary and secondary depositional processes. These can significantl y influence the potential applicability of tephra depos- its as isochronous marker horizons and current techniques, used in isolation, may be insufficient to fully unravel these processes. Here we demonstrate the innovative application of X-ray ...
    • Volcanically hosted venting with indications of ultramafic influence at Aurora hydrothermal field on Gakkel Ridge 

      German, Christopher R.; Reeves, Eoghan; Türke, Andreas; Diehl, Alexander; Albers, Elmar; Bach, Wolfgang; Purser, Autun; Ramalho, Sofia P.; Suman, Stefano; Mertens, Christian; Walter, Maren; Ramirez-Llodra, Eva; Schlindwein, Vera; Bünz, Stefan; Boetius, Antje (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-31)
      The Aurora hydrothermal system, Arctic Ocean, hosts active submarine venting within an extensive field of relict mineral deposits. Here we show the site is associated with a neovolcanic mound located within the Gakkel Ridge rift-valley floor, but deep-tow camera and sidescan surveys reveal the site to be ≥100 m across—unusually large for a volcanically hosted vent on a slow-spreading ridge and more ...
    • Water column methanotrophy controlled by a rapid oceanographic switch 

      Steinle, Lea; Graves, Carolyn A.; Treude, Tina; Ferré, Benedicte; Biastoch, Arne; Bussmann, Ingeborg; Berndt, Christian; Krastel, Sebastian; James, Rachel H.; Behrens, Erik; Böning, Claus W.; Greinert, Jens; Sapart, Célia-Julia; Scheinert, Markus; Sommer, Stefan; Lehmann, Moritz F.; Niemann, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-04-20)
      Large amounts of the greenhouse gas methane are released from the seabed to the water column, where it may be consumed by aerobic methanotrophic bacteria. The size and activity of methanotrophic communities, which determine the amount of methane consumed in the water column, are thought to be mainly controlled by nutrient and redox dynamics. Here, we report repeated measurements of methanotrophic ...
    • Water mass exchange between the Nordic Seas and the Arctic Ocean on millennial time scale during MIS 4–2 

      Rasmussen, Tine Lander; Thomsen, Erik; Nielsen, Tove (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
      The climate of the last glaciation circa 65,000–25,000 years ago was interrupted by about 15 abrupt temperature fluctuations, the so-called Dansgaard-Oeschger events consisting of warm interstadials and cold stadials recorded in Greenland ice cores. The largest fluctuations occur in the North Atlantic region, but they have been registered over the most of the world. The events are linked to changes ...
    • 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 ...
    • Widespread and accelerating glacier retreat on the Lyngen Peninsula, northern Norway, since their 'Little Ice Age' maximum 

      Stokes, Chris R.; Andreassen, Liss Marie; Champion, Matthew R; Corner, Geoffrey D. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-06)
      The recession of mountain glaciers worldwide is increasing global sea level and, in many regions, human activities will have to adapt to changes in surface hydrology. Thus, it is important to provide up-to-date analyses of glacier change and the factors modulating their response to climate warming. Here we report changes in the extent of >120 glaciers on the Lyngen Peninsula, northern Norway, where ...
    • Widespread natural methane and oil leakage from sub-marine Arctic reservoirs 

      Serov, Pavel; Mattingsdal, Rune; Winsborrow, Monica; Patton, Henry; Andreassen, Karin Marie (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-30)
      Parceling the anthropogenic and natural (geological) sources of fossil methane in the atmosphere remains problematic due to a lack of distinctive chemical markers for their discrimination. In this light, understanding the distribution and contribution of potential geological methane sources is important. Here we present empirical observations of hitherto undocumented, widespread and extensive methane ...
    • Widespread partial-depth hydrofractures in ice sheets driven by supraglacial streams 

      Chandler, David Matthew; Hubbard, Alun (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-19)
      Dramatic supraglacial lake drainage events in Greenland and Antarctica are enabled by rapid hydrofracture propagation through ice over 1 km thick. Here we present a slower mode of hydrofracture, where hairline surface fractures intersect supraglacial streams, and hypothesize that penetration depth is critically limited by water supply and englacial refreezing. We develop a model of stream-fed ...
    • Widespread subseafloor gas hydrate in the Barents Sea and Norwegian Margin 

      Cook, A.E.; Portnov, Alexey; Heber, R.C.; Vadakkepuliyambatta, Sunil; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-01)
      The distribution and concentration of subseafloor natural gas hydrate across margins is not well understood, because these systems are challenging to image and quantify remotely. Furthermore, it is unknown if shallow hydrate systems are linked to deeper oil and gas reservoirs. Herein, we analyze petroleum industry well logs with data in the gas hydrate stability zone and find that low concentrations ...
    • WNW-ESE-striking Timanian faults in Svalbard 

      Koehl, Jean-Baptiste P. (Conference object; Konferansebidrag, 2019-10)
    • Wood Jams Or Beaver Dams? Pliocene Life, Sediment And Landscape Interactions In The Canadian High Arctic 

      Davies, Neil S.; Gosse, John C; Rouillard, Alexandra; Rybczynski, Natalia; Meng, Jing; Reyes, Alberto V.; Kiguktak, Jarloo (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-28)
      During the mid-Pliocene (Zanclean, ca. ~ 3.9 Ma), parts of the Canadian High Arctic experienced mean annual temperatures that were 14–228C warmer than today and supported diverse boreal-type forests. The landscapes of this vegetated polar region left behind a fragmented sedimentary record that crops out across several islands in the Canadian Arctic Archipelago as the Beaufort Formation and correlative ...