• Abiotic methane from ultraslow-spreading ridges can charge Arctic gas hydrates 

      Johnson, Joel E; Mienert, Jurgen; Plaza-Faverola, Andreia; Vadakkepuliyambatta, Sunil; Knies, Jochen; Bünz, Stefan; Andreassen, Karin; Ferré, Benedicte (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-05)
      Biotic gas generation from the degradation of organic carbon in marine sediments supplies and maintains gas hydrates throughout the world’s oceans. In nascent, ultraslow-spreading ocean basins, methane generation can also be abiotic, occurring during the high-temperature (>200 °C) serpentinization of ultramafic rocks. Here, we report on the evolution of a growing Arctic gas- and gas hydrate–charged ...
    • Aligned glaciotectonic rafts on the central Barents Sea seafloor revealing extensive glacitectonic erosion during the last deglaciation 

      Ruther, Denise Christina; Andreassen, Karin; Spagnolo, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-12-07)
      Erosion rates on glaciated continental shelves are remarkably high, especially within ice stream troughs. Although glaciotectonic erosion may have considerably contributed to enhanced glacial erosion of these landscapes, entrainment mechanisms of glaciotectonically emplaced megablocks and rafts remain little understood. Here we report a northeast-southwest trending chain of over 1300 glacial rafts, ...
    • Arctic Ocean glacial history 

      Jakobsson, Martin; Andreassen, Karin; Bjarnadóttir, Lilja Rún; Dove, Dayton; Dowdeswell, Julian A.; England, John H.; Funder, Svend; Hogan, Kelly; Ingólfsson, Ólafur; Jennings, Anne; Krog Larsen, Nikolaj; Kirchner, Nina; Landvik, Jon Y.; Mayer, Larry; Mikkelsen, Naja; Möller, Per; Niessen, Frank; Nilsson, Johan; O'Reagan, Matt; Polyak, Leonid; Nørgaard-Pedersen, Niels; Stein, Ruediger (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-11-14)
      While there are numerous hypotheses concerning glacial–interglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the ...
    • Asynchronous response of marine-terminating outlet glaciers during deglaciation of the Fennoscandian Ice Sheet 

      Stokes, Chris R.; Corner, Geoffrey D.; Winsborrow, Monica; Husum, Katrine; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-03-31)
      Recent studies have highlighted the dynamic behavior of marine-terminating outlet glaciers over decadal time scales, linked to both atmospheric and oceanic warming. This helps explain episodes of nearly synchronous fl ow acceleration, thinning, and retreat, but nonclimatic factors such as changes in fjord width and depth, can also induce rapid recession. There is support for these topographic ...
    • The build-up, configuration, and dynamical sensitivity of the Eurasian ice-sheet complex to Late Weichselian climatic and oceanic forcing 

      Patton, Henry; Hubbard, Alun Lloyd; Andreassen, Karin; Winsborrow, Monica; Stroeven, Arjen P. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-01)
      The Eurasian ice-sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum (LGM), after the Antarctic and North American ice sheets. Despite its global significance, a comprehensive account of its evolution from independent nucleation centres to its maximum extent is conspicuously lacking. Here, a first-order, thermomechanical model, robustly constrained by empirical evidence, ...
    • A Continuous Seismostratigraphic Framework for the Western Svalbard-Barents Sea Margin Over the Last 2.7 Ma: Implications for the Late Cenozoic Glacial History of the Svalbard-Barents Sea Ice Sheet 

      Alexandropoulou, Nikolitsa; Winsborrow, Monica; Andreassen, Karin; Plaza-Faverola, Andreia; Dessandier, Pierre-Antoine; Mattingsdal, Rune; Baeten, Nicole; Knies, Jochen (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-14)
      Here we present a high-resolution, continuous seismostratigraphic framework that for the first time, connects the over 1,000 km long western Svalbard-Barents Sea margin and covers the last ∼2.7 million years (Ma). By exploiting recent improvements in chronology, we establish a set of reliable age fix-points from available boreholes along the margin. We then use a large 2-D seismic database to extend ...
    • 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 ...
    • Eurasian ice-sheet dynamics and sensitivity to subglacial hydrology 

      Gudlaugsson, Eythor; Humbert, Angelika; Andreassen, Karin; Clason, Caroline C.; Kleiner, Thomas; Beyer, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-24)
      Ice-stream dynamics are strongly controlled by processes taking place at the ice/bed interface where subglacial water both lubricates the base and saturates any existing, underlying sediment. Large parts of the former Eurasian ice sheet were underlain by thick sequences of soft, marine sediments and many areas are imprinted with geomorphological features indicative of fast flow and wet basal conditions. ...
    • Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming 

      Wallmann, Klaus; Riedel, M.; Hong, Wei-Li; Patton, Henry; Hubbard, Alun Lloyd; Pape, T.; Hsu, C.W.; Schmidt, C.; Johnson, Joel E.; Torres, M.E.; Andreassen, Karin; Berndt, C.; Bohrmann, G (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-08)
      Methane seepage from the upper continental slopes of Western Svalbard has previously been attributed to gas hydrate dissociation induced by anthropogenic warming of ambient bottom waters. Here we show that sediment cores drilled off Prins Karls Foreland contain freshwater from dissociating hydrates. However, our modeling indicates that the observed pore water freshening began around 8 ka BP when ...
    • Geologi og klimaendringer 

      Andreassen, Karin (Conference object; Konferansebidrag, 2010-09-02)
    • Geological controls of giant crater development on the Arctic seafloor 

      Waage, Malin; Serov, Pavel; Andreassen, Karin; Waghorn, Kate Alyse; Bünz, Stefan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-21)
      Active methane seepage occurs congruent with a high density of up to 1 km-wide and 35 m deep seafloor craters (>100 craters within 700 km<sup>2</sup> area) within lithified sedimentary rocks in the northern Barents Sea. The crater origin has been hypothesized to be related to rapid gas hydrate dissociation and methane release around 15–12 ka BP, but the geological setting that enabled and possibly ...
    • Geological controls on fluid flow and gas hydrate pingo development on the Barents Sea margin 

      Waage, Malin; Portnov, Aleksei D; Serov, Pavel; Bünz, Stefan; Waghorn, Kate Alyse; Vadakkepuliyambatta, Sunil; Mienert, Jurgen; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-16)
      In 2014, the discovery of seafloor mounds leaking methane gas into the water column in the northwestern Barents Sea became the first to document the existence of non‐permafrost related gas hydrate pingos (GHP) on the Eurasian Arctic shelf. The discovered site is given attention because the gas hydrates occur close to the upper limit of the gas hydrate stability, thus may be vulnerable to climatic ...
    • Geophysical constraints on the dynamics and retreat of the Barents Sea ice sheet as a palaeobenchmark for models of marine icesheet deglaciation 

      Patton, Henry; Andreassen, Karin; Bjarnadóttir, Lilja Rún; Dowdeswell, J.A.; Winsborrow, Monica; Noormets, Riko; Polyak, Leonid; Auriac, A.; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-14)
      Our understanding of processes relating to the retreat of marine-based ice sheets, such as the West Antarctic Ice Sheet and tidewater-terminating glaciers in Greenland today, is still limited. In particular, the role of ice-stream instabilities and oceanographic dynamics in driving their collapse are poorly constrained beyond observational timescales. Over numerous glaciations during the Quaternary, ...
    • Grounding line proximal sediment characteristics at a marine-based, late-stage ice stream margin 

      Rüther, Denise Christina; Winsborrow, Monica; Andreassen, Karin; Forwick, Matthias (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-05-12)
      Geomorphological evidence suggests that ice streams undergo frequent dynamic changes towards the end of their life cycles, but the associated sedimentary characteristics and processes remain poorly understood. Here, we present new sedimentological data from a Late Weichselian marine‐based ice stream in upper Bjørnøyrenna, northern Barents Sea, which experienced accelerated flow, intense calving of ...
    • High-resolution landform assemblage along a buried glacio-erosive surface in the SW Barents Sea revealed by P-Cable 3D seismic data 

      Bellwald, Benjamin; Planke, Sverre; Lebedeva-Ivanova, Nina; Piasecka, Emilia Daria; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-01)
      The Quaternary sedimentary record in the Arctic captures a diverse and evolving range of landscapes reflecting cli-mate changes. Here we study the geological landform assemblage of the Upper Regional Unconformity (URU) in theSW Barents Sea. The aims are (i) to characterize buried geological landforms on a meter-scale resolution, (ii) to un-derstand their link with underlying structures, and (iii) ...
    • Ice-stream dynamics of the SW Barents Sea revealed by high-resolution 3D seismic imaging of glacial deposits in the Hoop area 

      Bellwald, Benjamin; Planke, Sverre; Piasecka, Emilia Daria; Matar, M.A.; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-07)
      Recent developments in seismic acquisition systems and seismic data visualization have contributed to improve the imaging of seismic geomorphologies over a broad range of topics. This study focuses on a new high-resolution P-Cable 3D seismic cube located in the Hoop area in the SW Barents Sea. The scientific motivations of the study are (1) to document glacial landforms on a meter-scale, (2) to study ...
    • Ice‐margin retreat and grounding‐zone dynamics during initial deglaciation of the Storfjordrenna Ice Stream, western Barents Sea 

      Shackleton, Calvin; Winsborrow, Monica; Andreassen, Karin; Lucchi, Renata Giulia; Bjarnadóttir, Lilja Rún (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-11)
      Processes occurring at the grounding zone of marine terminating ice streams are crucial to marginal stability, influencing ice discharge over the grounding‐line, and thereby regulating ice‐sheet mass balance. We present new marine geophysical data sets over a ~30×40 km area from a former ice‐stream grounding zone in Storfjordrenna, a large cross‐shelf trough in the western Barents Sea, south of ...
    • The influence of a model subglacial lake on ice dynamics and internal layering 

      Gudlaugsson, Eythor; Humbert, Angelika; Kleiner, Thomas; Kohler, Jack; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-04-05)
      As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic ...
    • Large subglacial meltwater features in the central Barents Sea 

      Bjarnadóttir, Lilja Rún; Winsborrow, Monica; Andreassen, Karin (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-01)
      During the last glacial period large parts of the Arctic, including the Barents Sea, north of Norway and Russia, were covered by ice sheets. Despite several studies indicating that melting occurred beneath much of the Barents Sea ice sheet, very few meltwater-related landforms have been identified. We document ∼200 seafloor valleys in the central Barents Sea and interpret them to be tunnel valleys ...