Blar i forfatter "Knies, Jochen Manfred"

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    • 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 ...

    • 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 ...

    • 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-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 ...