Blar i forfatter "Knies, Jochen Manfred"

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    • Acoustic evidence of hydrocarbon release associated with the Spitsbergen Transform Fault, north of the Molloy Ridge, Fram Strait 

      Chand, Shyam; Knies, Jochen Manfred; Geissler, Wolfram H.; Plaza Faverola, Andreia Aletia; Thorsnes, Terje (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-16)
      Hydrocarbon gases formed from biotic and abiotic processes are released through the seafloor at different locations around the world. They have been widely observed directly in video and photo data, and indirectly on echosounder data. Even though biotic gas generation is a very common process, abiotic gas generation is limited to regions where serpentinization of ultramafic rocks occur. Indications ...

    • Continental weathering and recovery from ocean nutrient stress during the Early Triassic Biotic Crisis 

      Knies, Jochen Manfred; Schönenberger, Jasmin; Zwingmann, Horst; van der Lelij, Roelant; Smelror, Morten; Vullum, Per Erik; Vogt, Christoph; Fredin, Ola; Muller, Alxel; Grasby, Stephen E.; Beauchamp, Benoit; Viola, Giulio; Brönner, Marco (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-15)
      Following the latest Permian extinction ∼252 million years ago, normal marine and terrestrial ecosystems did not recover for another 5-9 million years. The driver(s) for the Early Triassic biotic crisis, marked by high atmospheric CO2 concentration, extreme ocean warming, and marine anoxia, remains unclear. Here we constrain the timing of authigenic K-bearing mineral formation extracted from ...

    • Editorial: Natural methane emissions in a changing arctic – implications for climate and environment 

      Andreassen, Karin Marie; Ruppel, Carolyn; Liebner, Susanne; Hodson, Andrew; Knies, Jochen Manfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-10-23)
      Natural methane emissions have received significant attention in recent years due to the documented increase in atmospheric concentrations of methane and its elevated global warming potential relative to CO2. Over the past decades, the Arctic has been warming nearly four times faster than the rest of the planet (Rantanen et al., 2022). Arctic amplification of global warming drives a pressing need ...

    • Evidence of Arctic methane emissions across the mid-Pleistocene 

      Panieri, Giuliana; Knies, Jochen Manfred; Vadakkepuliyambatta, Sunil; Lee, Amicia; Schubert, Carsten J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-08)
      During the Pleistocene, Earth’s climate changed dramatically. The mid-Pleistocene transition (MPT; ~1.3–0.7 million years (Ma)) featured an important ice volume increase at both poles. The evolution of large Arctic ice sheets caused the sequestration of methane as free gas and hydrates in subseabed sediments. Ice volume changes, associated with variable pressures and temperatures, perturbed those ...

    • Glacial erosion and quaternary landscape development of the Eurasian Arctic 

      Patton, Henry Jared; Alexandropoulou, Nikolitsa; Lasabuda, Amando P. E.; Knies, Jochen Manfred; Andreassen, Karin Marie; Winsborrow, Monica Caroline Mackay; Laberg, Jan Sverre; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-09-19)
      Multiple ice age cycles spanning the last three million years have fundamentally transformed the Arctic landscape. The cadence, intensity and pattern of this glacial modification underpin the stability of Arctic geosystems over geologic time scales, including its hydrology, circulation patterns, slope stability, hydrocarbon fluid flow, geochemical/sediment cycling and nutrient supply. The Barents ...

    • Glacial troughs as centres of organic carbon accumulation on the Norwegian continental margin 

      Diesing, Markus; Paradis, Sarah; Jensen, Henning; Thorsnes, Terje; Bjarnadóttir, Lilja Rún; Knies, Jochen Manfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-06-15)
      The role of continental margin sediments in the carbon cycle and the associated management potential for climate mitigation are currently poorly understood. Previous work has indicated that margin sediments store significant amounts of organic carbon, but few studies have quantified the rates at which organic carbon is accumulated. Here, we use machine learning to make spatial predictions of the ...

    • Lack of detectable chemosynthesis at a sponge dominated subarctic methane seep 

      Sinner, Melina; Hong, Wei-Li; Michel, Loïc N.; Vadakkepuliyambatta, Sunil; Knies, Jochen Manfred; Sen, Arunima (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-20)
      We used high-resolution imagery within a Geographic Information System (GIS), free gas and porewater analyses and animal bulk stable isotope measurements to characterize the biotic and abiotic aspects of the newly discovered Vestbrona Carbonate Field (VCF) seep site on the Norwegian shelf (63°28′N, 6° 31′E, ∿270 m water depth). Free gas was mainly composed of microbial methane. Sediment porewater ...

    • New cold seep sites on the continental slope southwest to Svalbard 

      Bellec, Valerie Karin; Chand, Shyam; Knies, Jochen Manfred; Bjarnadóttir, Lilja Rún; Lepland, Aivo; Sen, Arunima; Thorsnes, Terje (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-09)
      We discovered seafloor features such as bacterial mats and carbonate crusts typical for active methane seeps on the continental slope southwest of Svalbard. These features are associated with two main northwest-southeast trending morphological structures that are oriented parallel to the regional continental slope. Both structures occur at c. 800 m water depth, at the boundary between the Storfjorden ...

    • 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 ...

    • Protracted post-glacial hydrocarbon seepage in the Barents Sea revealed by U–Th dating of seep carbonates 

      Himmler, Tobias; Wagner, Doris; Sahy, Diana; Vadakkepuliyambatta, Sunil; Chand, Shyam; Martma, Tõnu; Kirsimäe, Kalle; Mattingsdal, Rune; Panieri, Giuliana; Bünz, Stefan; Condon, Daniel J.; Knies, Jochen Manfred; Lepland, Aivo (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-01)
      The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U–Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156–383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west ...

    • Sea ice variability from the penultimate glacial to the last interglacial in the Eastern Fram Strait 

      Steinsland, Kristine; Grant, Danielle M.; Fahl, Kirsten; Stein, Ruediger; Rasmussen, Tine Lander; Risebrobakken, Bjørg; Ninnemann, Ulysses S; Knies, Jochen Manfred; Velle, Julie Heggdal; De Schepper, Stijn (Journal article; Tidsskriftartikkel; Peer reviewed, 2025-01-28)
      The ongoing reduction of Arctic sea ice underscores the need to understand the drivers behind sea ice variability and associated ocean-climate impacts. The Last Interglacial, Marine Isotope (sub)Stage (MIS) 5e, and its transitions offer insights into sea ice variability during a period warmer than pre-industrial, and intervals of large climatic changes. This study examines a marine sediment core ...

    • Sea ice-ocean coupling during Heinrich Stadials in the Atlantic–Arctic gateway 

      el Bani Altuna, Naima; Mohamed, Mohamed Mahmoud Ezat Ahmed; Smik, Lukas; Muschitiello, Francesco; Belt, Simon T.; Knies, Jochen Manfred; Rasmussen, Tine Lander (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-11)
      The variability of Arctic sea-ice during abrupt stadial-interstadial shifts in the last glacial period remain poorly understood. Here, we investigated the millennial-scale relationship, with a focus on Heinrich Stadials (HS), between sea-ice cover and bottom water temperature (BWT) during Marine Isotope Stages (MIS) 3 and 2 (64–13 ka) in the Fram Strait using new molecular sea ice biomarker data and ...

    • Sedimentary deformation relating to episodic seepage in the last 1.2 million years: a multi-scale seismic study from the Vestnesa Ridge, eastern Fram Strait 

      Cooke, Frances Ann; Plaza-Faverola, Andreia; Bünz, Stefan; Sultan, Nabil; Ramachandran, Hariharan; Bedle, Heather; Patton, Henry; Singhroha, Sunny; Knies, Jochen Manfred (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-30)
      Seafloor hydrocarbon seepage is a natural fluid release process that occurs worldwide on continental shelves, slopes, and in deep oceanic basins. The Vestnesa sedimentary ridge in the eastern Fram Strait hosts a deep-water gas hydrate system that became charged with hydrocarbons ~2.7 Ma and has experienced episodic seepage along the entire ridge until a few thousand years ago, when seepage ...