Viser treff 106-125 av 701

    • Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities 

      Ryan, Jonathan C.; Hubbard, Alun Lloyd; Stibal, Marek; Irvine-Fynn, Tristam D.; Cook, Joseph; Smith, Lawrence C.; Cameron, Karen; Box, Jason E (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-14)
      Albedo—a primary control on surface melt—varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25 km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities—an ...
    • Dating submarine landslides using the transient response of gas hydrate stability 

      Portnov, Aleksei D; You, Kehua; Flemings, Peter B.; Cook, Ann E.; Heidari, Mahdi; Sawyer, Derek E.; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-02)
      Submarine landslides are prevalent on the modern-day seafloor, yet an elusive problem is constraining the timing of past slope failure. We present a novel age-dating technique based on perturbations to underlying gas hydrate stability caused by slide-impacted seafloor changes. Using three-dimensional (3-D) seismic data, we mapped an irregular bottom simulating reflection (BSR) underneath a submarine ...
    • 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, ...
    • Deciphering late Devonian–early Carboniferous P–T–t path of mylonitized garnet-mica schists from Prins Karls Forland, Svalbard 

      Kośmińska, Karolina; Spear, Frank S.; Majka, Jarosław; Faehnrich, Karol; Manecki, Maciej; Piepjohn, Karsten; Dallmann, Winfried (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-03)
      Quartz‐in‐garnet inclusion barometry integrated with trace element thermometry and calculated phase relations is applied to mylonitized schists of the Pinkie unit cropping out on the island of Prins Karls Forland, western part of the Svalbard Archipelago. This approach combines conventional and novel techniques and allows deciphering of the pressure–temperature (<i>P–T</i>) evolution of mylonitic ...
    • 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 ...
    • Deep ocean 14C ventilation age reconstructions from the Arctic Mediterranean reassessed 

      Ezat, Mohamed; Rasmussen, Tine Lander; Skinner, Luke C.; Zamelczyk, Katarzyna (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-05-13)
      The present-day ocean ventilation in the Arctic Mediterranean (Nordic Seas and Arctic Ocean), via transformation of northward inflowing warm Atlantic surface water into cold deep water, affects regional climate, atmospheric circulation and carbon storage in the deep ocean. Here we study the glacial evolution of the Arctic Mediterranean circulation and its influence on glacial climate using ...
    • Deep ocean storage of heat and CO2 in the Fram Strait, Arctic Ocean during the last glacial period 

      Ezat, Mohamed; Rasmussen, Tine Lander; Hain, Mathis P.; Greaves, Mervyn; Rae, James W.B.; Zamelczyk, Katarzyna; Marchitto, Thomas M.; Szidat, Sönke; Skinner, Luke C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-19)
      The Fram Strait is the only deep gateway between the Arctic Ocean and the Nordic Seas and thus is a key area to study past changes in ocean circulation and the marine carbon cycle. Here, we study deep ocean temperature, δ18O, carbonate chemistry (i.e., carbonate ion concentration [CO32−]), and nutrient content in the Fram Strait during the late glacial (35,000–19,000 years BP) and the Holocene based ...
    • Deep-time Arctic climate archives: high-resolution coring of Svalbard's sedimentary record – SVALCLIME, a workshop report 

      Senger, Kim; Kulhanek, Denise; Jones, Morgan T.; Smyrak-Sikora, Aleksandra; Planke, Sverre; Zuchuat, Valentin; foster, William J.; Grundvåg, Sten-Andreas; Lorenz, Henning; Ruhl, Micha; Sliwinska, Kasia K.; Vickers, Madeleine L.; Xu, Weimu (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-26)
      ​​​​​​​We held the MagellanPlus workshop SVALCLIME “Deep-time Arctic climate archives: high-resolution coring of Svalbard's sedimentary record”, from 18 to 21 October​​​​​​​ 2022 in Longyearbyen, to discuss scientific drilling of the unique high-resolution climate archives of Neoproterozoic to Paleogene age present in the sedimentary record of Svalbard. Svalbard is globally unique in that it facilitates ...
    • Deep-water sand transfer by hyperpycnal flows, the Eocene of Spitsbergen, Arctic Norway 

      Grundvåg, Sten-Andreas; Helland-Hansen, William; Johannessen, Erik P.; Eggenhuisen, Joris T.; Pohl, Florian; Spychala, Yvonne T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-11)
      Flood-generated hyperpycnal flows are dense, sediment-laden, turbulent flows that can form long-lived, bottom-hugging turbidity currents, which undoubtedly transport large volumes of fine-grained sediments into the ocean. However, their ability in transferring sand into deep-water basins is debated. This study presents sedimentological evidence of sandy hyperpycnal flow deposits (hyperpycnites) in ...
    • Deformation Behavior and Inferred Seismic Properties of Tonalitic Migmatites at the Time of Pre‐melting, Partial Melting, and Post‐Solidification 

      Shao, Yilun; Piazolo, Sandra; Liu, Yongjiang; Lee, Amicia; Jin, Wei; Li, Weimin; Liang, Chenyue; Wen, Quanbo (Journal article; Tidsskriftartikkel, 2021-01-21)
      As seismic data from the lower crust becomes more readily available, it is important to link seismic properties to the ongoing processes within lower crustal evolution. This includes high temperature, pre‐ and post‐migmatization solid state deformation as well as melt‐present deformation. We selected two tonalitic migmatites with variable former melt content (one metatexite and one diatexite) from ...
    • Deformation mechanisms accommodating progressive simple shear thrusting of quartzite and metacarbonate in the southwestern Espinhaço Range, Brazil 

      Taufner, Rhander; Lagoeiro, Leonardo E.; Cavalcante, Carolina; Barbosa, Paola; Silveira, Camila Santos (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-09)
      The accommodation of low-temperature ductile deformation in foreland fold-and-thrust belts is often described in terms of outcrop-based geometric analysis, but microtextural observations are also important, as they relate stress, strain, fluids and temperature and thus the rheology in the peripheral part of the orogen. Such microtextural observations are lacking from the foreland part of the Araçuaí ...
    • Deglacial dynamics of the Vestfjorden - Trænadjupet palaeo-ice stream, northern Norway 

      Laberg, Jan Sverre; Eilertsen, Raymond S; Salomonsen, Gaute R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-18)
      Few well‐dated records of the deglacial dynamics of the large palaeo‐ice streams of the major Northern Hemisphere ice sheets are presently available, a prerequisite for an improved understanding of the ice‐sheet response to the climate warming of this period. Here we present a transect of gravity‐core samples through Trænadjupet and Vestfjorden, northern Norway, the location of the Trænadjupet – ...
    • Deglacial–Holocene Svalbard paleoceanography and evidence of Melt Water Pulse 1B 

      Tian, Skye Y.; Yasuhara, Moriaki; Hong, Y.; Huang, H.-H.; Iwatani, H.; Chiu, W.-T. R.; Mamo, Bryoni; Okahashi, Hisayo; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-09)
      Better understanding of deglacial meltwater pulses (MWPs) is imperative for future predictions of human-induced warming and abrupt sea-level change because of their potential for catastrophic damage. However, our knowledge of the second largest meltwater pulse MWP-1B that occurred shortly after the start of the Holocene interglacial remains very limited. Here, we studied fossil ostracods as ...
    • Deglaciation of the central Barents Sea 

      Bjarnadóttir, Lilja Rún; Winsborrow, Monica C. M.; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-05-15)
      The marine-based Barents Sea Ice Sheet covered the polar continental shelf north of Norway and western Russia during the Last Glacial Maximum. Initial ice sheet retreat along the western margin is well established, while the retreat pattern in the interior parts of the ice sheet remains poorly known. Here we present new geological data from the central Barents Sea. The results are based on analysis ...
    • Deglaciation of the Eurasian ice sheet complex 

      Patton, Henry; Hubbard, Alun Lloyd; Andreassen, Karin; Auriac, Amandine; Whitehouse, Pippa L.; Stroeven, Arjen P.; Shackleton, Calvin; Winsborrow, Monica; Heyman, Jakob; Hall, Adrian M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-14)
      The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the ...
    • 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) ...
    • Depositional environments and source rock potential of some Upper Palaeozoic (Devonian) coals on Bjørnøya, Western Barents shelf 

      Janocha, Julian; Wesenlund, Fredrik; Thießen, Olaf; Grundvåg, Sten-Andreas; Koehl, Jean-Baptiste Philippe; Johannessen, Erik P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-02-27)
      Upper Palaeozoic strata are potential sources for hydrocarbon plays on the Norwegian Barents Shelf. The island of Bjørnøya (Bear Island) is located on the western margin of the Barents Shelf and represents an exposed part of the Stappen High, which makes it an excellent location to investigate the source rock potential of this succession. Here, we investigate the organic geochemical composition and ...
    • Depositional processes on the distal Scoresby Trough Mouth Fan (ODP Site 987): Implications for the Pleistocene evolution of the Scoresby Sund Sector of the Greenland Ice Sheet 

      Laberg, Jan Sverre; Rydningen, Tom Arne; Forwick, Matthias; Husum, Katrine (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-28)
      The investigation of trough mouth fans (TMFs), important paleoclimatic archives on mid- and high-latitude continental margins, has so far mainly been based on the integration of various types of acoustic data supplemented with short sediments cores. In consequence, sedimentological and chronological data about parts of TMFs deposited prior to the Last Glacial Maximum remains sparse. Here, we re-evaluate ...
    • Derivation of High Spatial Resolution Albedo from UAV Digital Imagery: Application over the Greenland Ice Sheet 

      Ryan, Jonathan C.; Hubbard, Alun Lloyd; Box, Jason E.; Brough, Stephen; Cameron, Karen; Cook, Joseph M.; Cooper, Matthew; Doyle, Samuel H.; Edwards, Arwyn; Holt, Tom; Irvine-Fynn, Tristram; Jones, Christine; Pitcher, Lincoln H.; Rennermalm, Åsa K.; Smith, Laurence C.; Stibal, Marek; Snooke, Neal (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-23)
      Measurements of albedo are a prerequisite for modeling surface melt across the Earth’s cryosphere, yet available satellite products are limited in spatial and/or temporal resolution. Here, we present a practical methodology to obtain centimeter resolution albedo products with accuracies of ±5% using consumer-grade digital camera and unmanned aerial vehicle (UAV) technologies. Our method comprises ...
    • Detection of gas hydrates in faults using azimuthal seismic velocity analysis,Vestnesa Ridge, W-Svalbard Margin 

      Singhroha, Sunny; Bünz, Stefan; Plaza Faverola, Andreia Aletia; Chand, Shyam (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-24)
      Joint analysis of electrical resistivity and seismic velocity data is primarily used todetect the presence of gas hydrate-filled faultsand fractures. In this study, we present a novel approach to inferthe occurrence of structurally-controlled gas hydrateaccumulations using azimuthal seismic velocity analysis. We perform thisanalysis using ocean-bottom seismic (OBS) data at two sites on Vestnesa ...