Viser treff 419-438 av 698

    • Natural variability of benthic foraminiferal assemblages and metal concentrations during the last 150 years in the Ingøydjupet trough, SW Barents Sea. 

      Dijkstra, Noortje; Junttila, Juho; Husum, Katrine; Carroll, JoLynn; Hald, Morten (Journal article; Tidsskriftartikkel, 2015-12)
      While today the SW Barents Sea is a relatively un-impacted and uncontaminated area, industrial activities related to the petroleum industry are projected to increase in the coming decades. This makes the area a valuable natural laboratory to establish pre-impacted baselines as a precursor for future seabed monitoring programs. Here we present benthic foraminiferal assemblages and metal concentrations ...
    • Neodymium isotope constraints on chemical weathering and past glacial activity in Svalbard 

      Jang, Kwangchul; Bayon, Germain; Han, Yeongcheol; Joo, Young Ji; Kim, Ji-Hoon; Ryu, Jong-Sik; Woo, Jusun; Forwick, Matthias; Szczuciński, Witold; Kim, Jung-Hyun; Nam, Seung-Il (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-15)
      <p>Neodymium (Nd) isotopes in leached authigenic components of marine sediments have been increasingly used as a tracer of past ocean-water masses. Despite the general assumption that the Nd isotopic composition of solutes released during chemical weathering fingerprints the source rocks on continents, preferential dissolution of easily dissolvable phases may result in significant deviations in Nd ...
    • Neogene dinoflagellate cysts and acritarchs from the high northern latitudes and their relation to sea surface temperature 

      Schreck, Michael; Nam, Seung-Il; Clotten, Caroline; Fahl, Kirsten; De Schepper, Stijn; Forwick, Matthias; Matthiessen, Jens (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-09-13)
      <p>Organic-walled dinoflagellate cysts and acritarchs are a vital tool for reconstructing past environmental change, in particular in the Neogene of the high northern latitudes where marine deposits are virtually barren of traditionally used calcareous microfossils. Yet only little is known about the paleoenvironmental value of fossil assemblages that do not have modern analogues, so that reconstructions ...
    • Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and p/T analysis of fault rocks 

      Koehl, Jean-Baptiste P.; Bergh, Steffen G; Wemmer, Klaus (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-20)
      Well-preserved fault gouge along brittle faults in Paleoproterozoic, volcano-sedimentary rocks of the Raipas Supergroup exposed in the Alta–Kvænangen tectonic window in northern Norway yielded latest Mesoproterozoic (approximately 1050 15 Ma) to mid-Neoproterozoic (approximately 825–810 18 Ma) K–Ar ages. Pressure–temperature estimates from microtextural and mineralogy analyses of fault ...
    • 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 ...
    • New geophysical evidence for a revised maximum position of part of the NE sector of the Greenland ice sheet during the last glacial maximum 

      Laberg, Jan Sverre; Forwick, Matthias; Husum, Katrine; Laberg, Jan Sverre (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-26)
      The extent and dynamics of the north-eastern sector of the Greenland ice sheet (GIS) during the last glacial still remain very uncertain, and maximum ice extents to inner-shelf, mid-shelf and outer-shelf positions have been suggested. Here we argue that the margin of the GIS reached the shelf break along part of its NE sector during the last glacial maximum. Swath-bathymetry and sub-bottom profiler ...
    • A new methodology for quantifying bubble flow rates in deep water using splitbeam echosounders: Examples from the Arctic offshore NW-Svalbard 

      Veloso, M.; Greinert, Jens; Mienert, Jurgen; De Batist, M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-05-08)
      Quantifying marine methane fluxes of free gas (bubbles) from the seafloor into the water column is of importance for climate related studies, for example, in the Arctic, reliable methodologies are also of interest for studying man-made gas and oil leakage systems at hydrocarbon production sites. Hydroacoustic surveys with singlebeam and nowadays also multibeam systems have been proven to be a ...
    • A new numerical model for understanding free and dissolved gasprogression toward the atmosphere in aquatic methane seepage systems 

      Jansson, Pär; Ferré, Benedicte; Silyakova, Anna; Dølven, Knut Ola; Omstedt, Anders (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-16)
      We present a marine two‐phase gas model in one dimension (M2PG1) resolving interaction between the free and dissolved gas phases and the gas propagation toward the atmosphere in aquatic environments. The motivation for the model development was to improve the understanding of benthic methane seepage impact on aquatic environments and its effect on atmospheric greenhouse gas composition. Rising, ...
    • Nitrogen Isotope Evidence for Changing Arctic Ocean Ventilation Regimes During the Cenozoic 

      Knies, Jochen Manfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-03)
      In this work, I report on the coupling of dinitrogen (N<sub>2</sub>) fixation and denitrification in oxygen-deficient waters of the Arctic Ocean during the Paleogene. This coupling fertilized marine phytoplankton growth and favored organic carbon burial. Reduced vertical mixing due to salinity stratification in a tectonically closed oceanic basin created conditions favorable for N<sub>2</sub>-fixation ...
    • Nitrogen uptake by methanotrophic consortia in deep-water gas hydrate-bearing sediments 

      Argentino, Claudio; Wittig, Cathrin; Peckmann, Jörn; Panieri, Giuliana (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-19)
      Methane-consuming microbes inhabiting marine methane seeps have recently been found to have the capacity to assimilate inorganic nitrogen, suggesting a previously unaccounted role in the global nitrogen cycle. Despite ex-situ experimental observations, definitive evidence of this process under in-situ conditions remains elusive, hindering the complete understanding of the controlling factors and ...
    • Non-linear response of glacier melting to Holocene warming in Svalbard recorded by sedimentary iron (oxyhydr)oxides 

      Jang, Kwangchul; Bayon, Germain; Vogt, Christoph; Forwick, Matthias; Ahn, Youngkyu; Kim, Jung-Hyun; Nam, Seung-Il (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-01)
      The recent acceleration of ice-sheet loss with its direct impact on sea-level rise and coastal ecosystems is of major environmental and societal concern. However, the effect of atmospheric temperature increases on long-term glacier retreat remains poorly defined due to limited historical observations and uncertainties in numerical ice-sheet models, which challenges climate change adaptation planning. ...
    • Nonlinear Preisach maps: Detecting and characterizing separate remanent magnetic fractions in complex natural samples 

      Church, Nathan Stewart; Fabian, Karl; McEnroe, Suzanne (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-27)
      Natural remanent magnetization carriers in rocks can contain mixtures of magnetic minerals that interact in complex ways and are challenging to characterize by current measurement techniques. Here a nonlinear mapping scheme is described that efficiently enhances sensitivity and the resolution power of remanent Preisach maps. Using this scheme a large dynamic range of magnetic moments and coercivities ...
    • Nordic Seas polynyas and their role in preconditioning marine productivity during the Last Glacial Maximum 

      Knies, Jochen; Koseoglu, Denizcan; Rise, Leif; Baeten, Nicole; Bellec, Valerie K; Bøe, Reidulv; Klug, Martin; Panieri, Giuliana; Jernas, Patrycja Ewa; Belt, Simon T. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-27)
      Arctic and Antarctic polynyas are crucial sites for deep-water formation, which helps sustain global ocean circulation. During glacial times, the occurrence of polynyas proximal to expansive ice sheets in both hemispheres has been proposed to explain limited ocean ventilation and a habitat requirement for marine and higher-trophic terrestrial fauna. Nonetheless, their existence remains equivocal, ...
    • Norges grenser i dyphavet 

      Vorren, Tore Ola; Laberg, Jan Sverre (Chronicle; Kronikk, 2010-08-14)
    • A North Atlantic tephrostratigraphical framework for 130–60 ka b2k: new tephra discoveries, marine-based correlations, and future challenges 

      Davies, Siwan M.; Abbott, Peter M.; Meara., Rhian H.; Pearce, Nicholas J.G.; Austin, William E.N.; Chapman, Mark R.; Svensson, Anders; Bigler, Matthias; Rasmussen, Tine Lander; Rasmussen, Sune O.; Farmer, Elisabeth J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • North Atlantic warming during Dansgaard-Oeschger events synchronous with Antarctic warming and out-of-phase with Greenland climate 

      Rasmussen, Tine Lander; Thomsen, Erik; Moros, Matthias (Journal article; Peer reviewed; Tidsskriftartikkel, 2016-02-05)
      The precise reason for the differences and out-of-phase relationship between the abrupt Dansgaard- Oeschger warmings in the Nordic seas and Greenland ice cores and the gradual warmings in the southcentral Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that ...
    • Northeast Greenland (79.4 °N): Ice-free shelf edge around the Last Glacial Maximum 25.5-17.5 ka 

      Rasmussen, Tine Lander; Pearce, Christof; Andresen, Katrine Juul; Nielsen, Tove; Seidenkrantz, Marit Solveig (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-16)
      The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, ...
    • Northward advection of Atlantic water in the eastern Nordic Seas over the last 3000 yr 

      Dylmer, C. V.; Giraudeau, Jacques; Eynaud, F; Husum, Katrine; de Vernal, A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Three marine sediment cores distributed along the Norwegian (MD95-2011), Barents Sea (JM09-KA11-GC), and Svalbard (HH11-134-BC) continental margins have been investigated in order to reconstruct changes in the poleward flow of Atlantic waters (AW) and in the nature of upper surface water masses within the eastern Nordic Seas over the last 3000 yr. These reconstructions are based on a limited set ...
    • Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation? 

      Vanneste, Maarten; Mienert, Jurgen; Haflidason, H; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)
    • A novel biomarker-based proxy for the spring phytoplankton bloom in Arctic and sub-arctic settings – HBI T25 

      Belt, Simon T.; Smik, Lukas; Köseoğlu, Denizcan; Knies, Jochen; Husum, Katrine (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-19)
      The spring phytoplankton bloom is a characteristic feature of mid-high latitudes in modern times, but can be challenging to identify in palaeo records. In the current study, we investigated the absolute and relative distributions of two diatom-derived tri-unsaturated highly branched isoprenoid (HBI) lipids, at least one of which has previously been suggested to be a possible proxy for the productive ...