• 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 ...
    • 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 ...
    • 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) ...
    • 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 ...
    • Diagenetic alteration of benthic foraminifera from a methane seep site on Vestnesa Ridge (NW Svalbard) 

      Schneider, Andrea; Cremiere, Antoine; Panieri, Giuliana; Lepland, Aivo; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-03-08)
      Anomalously low δ<sup>13</sup>C values in foraminiferal calcite tests are due to diagenetic alteration in methane seep sites. Our study applies diagenetically altered fossil benthic foraminiferal tests as geochemical tracers in reconstructing natural past methane seepage episodes at Vestnesa Ridge offshore NW Svalbard. We combine examinations of the test wall microstructure, mineralogical and stable ...
    • Direct measurements of meltwater runoff on the Greenland ice sheet surface 

      Smith, Laurence C.; Yang, Kang; Pitcher, Lincoln H.; Overstreet, Brandon T.; Chu, Vena W.; Rennermalm, Åsa K.; Ryan, Jonathan C.; Cooper, Matthew G.; Gleason, Colin J.; Tedesco, Marco; Jeyaratnam, Jeyavinoth; van As, Dirk; van den Broeke, Michiel R.; van de Berg, Willem Jan; Noël, Brice; Langen, Peter L.; Cullather, Richard I.; Zhao, Bin; Willis, Michael J.; Hubbard, Alun Lloyd; Box, Jason E.; Jenner, Brittany A.; Behar, Alberto E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-05)
      Meltwater runoff from the Greenland ice sheet surface influences surface mass balance (SMB), ice dynamics, and global sea level rise, but is estimated with climate models and thus difficult to validate. We present a way to measure ice surface runoff directly, from hourly in situ supraglacial river discharge measurements and simultaneous high-resolution satellite/drone remote sensing of upstream ...
    • Distribution and characteristics of overdeepenings beneath the Greenland and Antarctic ice sheets: Implications for overdeepening origin and evolution 

      Patton, Henry; Swift, D.A.; Clark, C.D.; Livingstone, Stephen J.; Cook, S.J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-15)
      Glacier bed overdeepenings are ubiquitous in glacier systems and likely exert significant influence on ice dynamics, subglacial hydrology, and ice stability. Understanding of overdeepening formation and evolution has been hampered by an absence of quantitative empirical studies of their distribution and morphology, with process insights having been drawn largely from theoretical or numerical studies. ...
    • Distribution of living benthic foraminifera in the northern Chukchi Sea 

      Racine, Calypso; Bonnin, Jérôme; Nam, Seung-Il; Giraudeau, Jacques; Biguenet, Maude; Dessandier, Pierre-Antoine; Kim, Jung‑Hyun (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-27)
      Living (Rose Bengal stained) benthic foraminifera were studied in the topmost sediments of five multi- and box cores collected on the continental shelf, upper and lower slopes, of the Chukchi Sea to provide background information on modern benthic foraminiferal distribution, useful for future studies. Sediment cores were collected during August–September 2015, when the area is seasonally ice-free. ...
    • Divergent drift of Adriatic-Dinaridic and Moesian carbonate platforms during the rifting phase witnessed by Triassic MVT Pb-Zn and SEDEX deposits; a metallogenic approach 

      Palinkaš, Ladislav A.; Damyanov, Zhelyazko K.; Šoštarić, Sibila Borojević; Strmic Palinkas, Sabina; Marinova, Irina (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-29)
      Early-intracontinental rifting of Pangea was a result of thermal doming in Uppermost Permian time giving rise to the formation of horst-graben structures, followed by slow subsidence, marine transgression and evaporite deposition. The consequences of incipient magmatism and a high heat flow are numerous geothermal fields and subterrestrial hydrothermal siderite-barite-polysulfide deposits (PALINKAŠ ...
    • 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 ...
    • 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 ...
    • 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 ...
    • Energy barriers in three-dimensional micromagnetic models and the physics of thermoviscous magnetization 

      Fabian, Karl; Shcherbakov, Valera P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-17)
      A first-principle micromagnetic and statistical calculation of viscous remanent magnetization (VRM) in an ensemble of cubic magnetite pseudo-single domain (PSD) particles is presented. The theoretical methods developed apply to all magnetic particle sizes, from single domain to multidomain. The numerical implementation is based on a fast relaxation algorithm for finding optimal transition paths ...
    • Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane 

      Pohlman, John; Greinert, Jens; Ruppel, Carolyn; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-08)
      Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global ...
    • Environmental baselines and reconstruction of Atlantic Water inflow in Bjørnøyrenna, SW Barents Sea, since 1800 CE 

      Dijkstra, Noortje; Junttila, Juho; Sørensen, Steffen Aagaard (Journal article; Tidsskriftartikkel, 2017-10-28)
      Metal concentrations, sediment properties and benthic foraminiferal assemblages were investigated in sediment cores in the SW Barents Sea, to reconstruct environmental baselines and natural variability of Atlantic Water inflow since 1800 CE. Metal concentrations correspond to no effect levels and do not influence the foraminifera. Increased Hg and Pb was linked to inflow of Atlantic Water. The data ...
    • Environmental change in the Early Permian of NE Svalbard : from a warm-water carbonate platform (Gipshuken Formation) to a temperate, mixed siliciclastic-carbonate ramp (Kapp Starostin Formation) 

      Blomeier, Dierk; Dustira, Anna Marie; Forke, Holger; Scheibner, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      A detailed facies study of Early Permian strata within NE Svalbard reveals a fundamental change of the depositional setting, from a restricted-marine, warm-water carbonate platform to an open-marine, temperate-water, mixed siliciclastic-carbonate ramp. The uppermost strata of the Gipshuken Formation (Templet and Sørfonna members; Sakmarian–early Artinskian?) consist of microbialites (algal mats), ...
    • Episodic release of CO2 from the high-latitude North Atlantic Ocean during the last 135 kyrs 

      Ezat, Mohamed; Rasmussen, Tine Lander; Honisch, Barbel; Groeneveld, Jeroen; DeMenocal, P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-22)
      Antarctic ice cores document glacial-interglacial and millennial-scale variability in atmospheric pCO2 over the past 800 kyr. The ocean, as the largest active carbon reservoir on this timescale, is thought to have played a dominant role in these pCO2 fluctuations, but it remains unclear how and where in the ocean CO2 was stored during glaciations and released during (de)glacial millennial-scale ...