Now showing items 221-240 of 729

    • 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 ...
    • Dissolution precipitation creep as a process for the strain localisation in mafic rocks 

      Lee, Amicia; Stunitz, Holger; Soret, Mathieu; Battisti, Matheus Ariel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-01)
      The lower crust is, on average, mafic in composition and composed of minerals that remain mechanically strong up to high temperatures. Here we show that dissolution-precipitation creep (as a type of diffusion creep) plays a major role in deformation of gabbro bodies at upper amphibolite facies conditions. The Kågen gabbro, N. Norway, is comprised of undeformed gabbro lenses enclosed by mylonitised ...
    • A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude 

      Marschalek, J. W.; Zurli, L.; Talarico, F.; van de Flierdt, T.; Vermeesch, P.; Carter, A.; Beny, F.; Bout-Roumazeilles, V.; Sangiorgi, F.; Hemming, S. R.; Pérez, L. F.; Colleoni, F.; Prebble, J. G.; van Peer, T. E.; Perotti, M.; Shevenell, A. E.; Browne, I.; Kulhanek, D. K.; Levy, R.; Harwood, D.; Sullivan, N. B.; Meyers, S. R.; Griffith, E. M.; Hillenbrand, C. D.; Gasson, E.; Siegert, M. J.; Keisling, B.; Licht, K. J.; Kuhn, G.; Dodd, J. P.; Boshuis, C.; de Santis, L.; McKay, R. M.; Ash, J.; Cortese, G.; Esper, O. V.; Gales, J. A.; Ishino, S.; Kim, Sookwan; Kim, Sunghan; Laberg, Jan Sverre; Leckie, R. M.; Muller, J.; Patterson, M. O.; Romans, B. W.; Romero, O. E.; Seki, O.; Singh, S. M.; Cordeiro de Sousa, I. M.; Sugisaki, S. T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021)
      Early to Middle Miocene sea-level oscillations of approximately 40–60 m estimated from far-field records1,2,3 are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth2. This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene4,5. Data and model outputs can ...
    • Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo 

      Irvine-Fynn, Tristram D. L.; Bunting, Peter S.; Cook, Joseph M.; Hubbard, Alun; Barrand, Nicholas E.; Hanna, Edward; Hardy, Andy J.; Hodson, Andrew J.; Holt, Tom O.; Huss, Matthias; McQuaid, James B.; Nilsson, Johan; Naegeli, Kathrin; Roberts, Osian; Ryan, Jonathan C.; Tedstone, Andrew J.; Tranter, Martyn; Williamson, Christopher J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-23)
      Ice surface albedo is a primary modulator of melt and runoff, yet our understanding of how reflectance varies over time across the Greenland Ice Sheet remains poor. This is due to a disconnect between point or transect scale albedo sampling and the coarser spatial, spectral and/or temporal resolutions of available satellite products. Here, we present time-series of bare-ice surface reflectance data ...
    • Impact of Timanian thrust systems on the late Neoproterozoic–Phanerozoic tectonic evolution of the Barents Sea and Svalbard 

      Koehl, Jean-Baptiste Philippe; Magee, Craig; Anell, Ingrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-12)
      The Svalbard Archipelago consists of three basement terranes that record a complex Neoproterozoic– Phanerozoic tectonic history, including four contractional events (Grenvillian, Caledonian, Ellesmerian, and Eurekan) and two episodes of collapse- to rift-related extension (Devonian–Carboniferous and late Cenozoic). Previous studies suggest that these three terranes likely accreted during the early ...
    • How Academics and the Public Experienced Immersive Virtual Reality for Geo-Education 

      Bonali, Fabio L.; Russo, Elena; Vitello, Fabio; Antoniou, Varvara; Marchese, Fabio; Fallati, Luca; Bracchi, Valentina; Corti, Noemi; Savini, Alessandra; Whitworth, Malcom; Drymoni, Kyriaki; Mariotto, Federico Pasquaré; Nomikou, Paraskevi V.; Sciacca, Eva; Bressan, Sofia; Falsaperla, Susanna; Reitano, Danilo; van Wyk de Vries, Benjamin; Krokos, Mel; Panieri, Giuliana; Stiller-Reeve, Matthew Alexander; Vizzari, Giuseppe; Becciani, Ugo; Tibaldi, Alessandro (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-24)
      Immersive virtual reality can potentially open up interesting geological sites to students, academics and others who may not have had the opportunity to visit such sites previously. We study how users perceive the usefulness of an immersive virtual reality approach applied to Earth Sciences teaching and communication. During nine immersive virtual reality-based events held in 2018 and 2019 in ...
    • Mineral paragenesis and sulphide trace element distribution in the metamorphosed Lovisa Zn-Pb deposit, Bergslagen (Sweden), as revealed by 3D X-ray tomography, ore petrography and LA-ICP-MS analysis 

      Andersson, Stefan S.; Sahlström, Fredrik; Jonsson, Erik; Luth, Stefan; Lynch, Edward P.; Högdahl, Karin; Zack, Thomas; Gies, Nils; Sädbom, Stefan; Alexander Hansson, K.S.; Bergqvist, Mikael (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-29)
      This study encompasses the ore mineralogy, textures and sulphide trace element chemistry of the Palaeoproterozoic Lovisa stratiform Zn-Pb deposit and the stratigraphically underlying Lovisa Fe Formation in the Bergslagen ore province (Sweden). We investigate the relative timing of formation and subsequent modifications of its ores in relation to the c. 1.87–1.80 Ga Svecokarelian orogeny. The Lovisa ...
    • Physical weathering by glaciers enhances silicon mobilisation and isotopic fractionation 

      Hatton, J.E.; Hendry, K.R.; Hawkings, J.R.; Wadham, Jemma Louise; Benning, L.G.; Blukis, R.; Roddatis, V.; Ng, H.C.; Wang, T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-06)
      Glacial meltwaters export substantial quantities of dissolved and dissolvable amorphous silicon (DSi and ASi), providing an essential nutrient for downstream diatoms. Evidence suggests that glacially exported DSi is isotopically light compared to DSi in non-glaciated rivers. However, the isotopic fractionation mechanisms are not well constrained, indicating an important gap in our understanding ...
    • Origin and Periodic Behavior of Short Duration Signals Recorded by Seismometers at Vestnesa Ridge, an Active Seepage Site on the West-Svalbard Continental Margin 

      Domel, Przemyslaw; Singhroha, Sunny; Plaza-Faverola, Andreia; Schlindwein, Vera; Ramachandran, Hariharan; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-02)
      Short duration events (SDEs) are reported worldwide from ocean-bottom seismometers (OBSs). Due to their high frequency (4–30 Hz) and short duration, they are commonly attributed to aseismic sources, such as fluid migration related processes from cold seeps, biological signals, or noise. We present the results of a passive seismic experiment that deployed an OBS network for 10-month (October 2015–July ...
    • Glacier response to the Little Ice Age during the Neoglacial cooling in Greenland 

      Kjær, Kurt H.; Bjørk, Anders A.; Kjeldsen, Kristian K.; Hansen, Eric S.; Andresen, Camilla S.; Siggaard-Andersen, Marie-Louise; Khan, Shfaqat Abbas; Søndergaard, Anne Sofie; Colgan, William; Schomacker, Anders; Woodroffe, Sarah; Funder, Svend; Rouillard, Alexandra; Jensen, Jens Fog; Larsen, Nicolaj K. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-04)
      In the Northern Hemisphere, an insolation driven Early to Middle Holocene Thermal Maximum was followed by a Neoglacial cooling that culminated during the Little Ice Age (LIA). Here, we review the glacier response to this Neoglacial cooling in Greenland. Changes in the ice margins of outlet glaciers from the Greenland Ice Sheet as well as local glaciers and ice caps are synthesized Greenland-wide. ...
    • Development of the NORSAR Network over the Last 50 Yr 

      Schweitzer, Johannes; Köhler, Andreas; Christensen, Jon Magnus (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-27)
      This contribution describes the development of Norwegian Seismic Array (NORSAR), from its origin 50 yr ago as a project for installing a single seismic array in southern Norway to a seismological research institute operating a network of six arrays and 14 three‐component stations located in Norway and Antarctica. In addition, we document the different instrumentations from narrowband, mostly ...
    • Seismic and electrical geophysical characterization of an incipient coastal open-system pingo: Lagoon Pingo, Svalbard 

      Hammock, Craig Paul; Kulessa, Bernd; Hiemstra, John F.; Hodson, Andrew; Hubbard, Alun (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-24)
      Whilst there has been a recent appreciation for the role of open-system pingos in providing a fluid-flow conduit through continuous permafrost that enables methane release, the formation and internal structure of these ubiquitous permafrost-diagnostic landforms remains unclear. Here, we combine active-source seismic measurements with electrical resistivity tomography (ERT) to investigate the structural ...
    • Autonomous methane seep site monitoring offshore western Svalbard: hourly to seasonal variability and associated oceanographic parameters 

      Dølven, Knut Ola; Ferré, Benedicte; Silyakova, Anna; Jansson, Pär; Linke, Peter; Moser, Manuel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-18)
      Improved quantification techniques of natural sources are needed to explain variations in atmospheric methane. In polar regions, high uncertainties in current estimates of methane release from the seabed remain. We present unique 10- and 3-month time series of bottom water measurements of physical and chemical parameters from two autonomous ocean observatories deployed at separate intense seabed ...
    • Decadal trend of plankton community change and habitat shoaling in the Arctic gateway recorded by planktonic foraminifera 

      Greco, Mattia; Werner, Kristin; Zamelczyk, Katarzyna; Rasmussen, Tine Lander; Kucera, Michal (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-16)
      The Fram Strait plays a crucial role in regulating the heat and sea-ice dynamics in the Arctic. In response to the ongoing global warming, the marine biota of this Arctic gateway is experiencing significant changes with increasing advection of Atlantic species. The footprint of this ‘Atlantification’ has been identified in isolated observations across the plankton community, but a systematic, ...
    • A practical method to determine the five-parameter orientation of intragranular boundaries in polycrystals 

      Lloyd, Geoffrey E.; Lee, Amicia; Kahl, Maren (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-04)
      Intragranular boundaries are important features of polycrystalline materials and impact on many physical and chemical properties. Knowledge of their physical orientation is often crucial to explain such properties. However, it has proved difficult to determine the complete orientation of intragranular boundaries, which involves the misorientation angle and axis about which the adjacent crystal ...
    • Benthic foraminiferal assemblages and environmental drivers along the Kveithola Trough (NW Barents Sea) 

      Caridi, Francesca; Sabbatini, Anna; Bensi, Manuel; Kovačević, Vedrana; Lucchi, Renata Giulia; Morigi, Caterina; Povea, Patricia; Negri, Alessandra (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-14)
      We describe the population density, biodiversity and vertical distribution in the sediment of benthic foraminifera, and their relationship to environmental parameters, in the Kveithola Trough (NW Barents Sea). Two staining methods, Cell Tracker Green (CTG) and Rose Bengal (RB), were used to distinguish between living and dead tests. CTG proved to be more effective than RB, and we therefore used this ...
    • Sheared Peridotite and Megacryst Formation Beneath the Kaapvaal Craton: A Snapshot of Tectonomagmatic Processes across the Lithosphere-Asthenosphere Transition 

      Tappe, Sebastian; Massuyeau, Malcolm; Smart, Katie A; Woodland, Alan B; Gussone, Nikolaus; Milne, Sarah; Stracke, Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-27)
      The cratonic lithosphere–asthenosphere boundary is commonly invoked as the site of sheared peridotite and megacryst formation, a well-recognized petrological assemblage whose genetic relationships—if any—remain poorly understood. We have undertaken a comprehensive petrology and Sr–Nd–Hf–Ca isotope study of sheared peridotite xenoliths and clinopyroxene megacrysts from the c. 1150 Ma Premier kimberlite ...
    • Evolution and temporal constraints of a multiphase postglacial rock slope failure 

      Vick, Louise Mary; Mikkelsen, Martin; Corner, Geoffrey; Kjellman, Sofia Elisabeth; Trønnes, Leif; Hormes, Anne; Allaart, Lis; Bergh, Steffen G (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-05)
      Large rock slope failures are temporal processes which act to modify the landscape after glacial retreat. The slope failure process often shows a lag time of thousands of years after deglaciation, with multiple failure events possible. While global datasets constrain this lag time from extensive mapping and dating of paraglacial rock avalanches, the timeline is poorly refined in northern Norway. We ...
    • Heterogeneous REE + Y distribution in Early Paleozoic shelly phosphorites: Implications for enrichment mechanisms 

      Lumiste, Kaarel; Lang, Liisa; Paiste, Päärn; Lepland, Aivo; Kirsimäe, Kalle (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-27)
      Sedimentary phosphorites are important carriers of Rare Earth Elements and Yttrium (REE + Y). Primary biogenic and sedimentary apatite contain very low amounts of REE + Y and enrichment of these elements occurs during diagenesis. Although the influence of post-depositional processes on REE + Y concentrations in sedimentary phosphorites is well established, the processes controlling the degree of ...
    • Regional Morpho-Kinematic Inventory of Slope Movements in Northern Norway 

      Rouyet, Line; Lilleøren, Karianne Staalesen; Böhme, Martina; Vick, Louise Mary; Delaloye, Reynald; Etzelmüller, Bernd; Lauknes, Tom Rune; Larsen, Yngvar; Blikra, Lars Harald (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-25)
      Mountain slopes in periglacial environments are affected by frost- and gravity-driven processes that shape the landscape. Both rock glaciers and rockslides have been intensively inventoried worldwide. Although most inventories are traditionally based on morphologic criteria, kinematic approaches based on satellite remote sensing have more recently been used to identify moving landforms at the regional ...