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  • 1
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    Gas hydrate distribution and hydrocarbon maturation north of the Knipovich Ridge, western Svalbard margin (2016)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Solid Earth, Wiley, ISSN: 0148-0227
    Details
    Publication Date: 2016-02-02
    Description: A bottom-simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow-spreading ridge segment of the Mid Atlantic Ridge system. Here, heat flow is high (up to 330 mW m-2), increasing towards the ridge axis. The coinciding maxima in across-margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic-rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 2
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    An 1888 Volcanic Collapse Becomes a Benchmark for Tsunami Models (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Eos: Earth & Space Science News, 48 .
    Details
    Publication Date: 2021-05-11
    Description: When volcanic mountains slide into the sea, they trigger tsunamis. How big are these waves, and how far away can they do damage? Ritter Island provides some answers.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2017EO083743
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Gas hydrate distribution and hydrocarbon maturation north of the Knipovich Ridge, western Svalbard margin (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Solid Earth, 121 (3). pp. 1405-1424.
    Details
    Publication Date: 2019-09-23
    Description: A bottom-simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow-spreading ridge segment of the Mid Atlantic Ridge system. Here, heat flow is high (up to 330 mW m-2), increasing towards the ridge axis. The coinciding maxima in across-margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic-rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1002/2015JB012083
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Seismic reflection imaging of mixing processes in Fram Strait (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Oceans, 120 (10). pp. 6884-6896.
    Details
    Publication Date: 2019-04-04
    Description: The West Spitsbergen Current, which flows northward along the western Svalbard continental slope, transports warm and saline Atlantic water (AW) into the Arctic Ocean. A combined analysis of highresolution seismic images and hydrographic sections across this current has uncovered the oceanographic processes involved in horizontal and vertical mixing of AW. At the shelf break, where a strong horizontal temperature gradient exists east of the warmest AW, isopycnal interleaving of warm AW and surrounding colder waters is observed. Strong seismic reflections characterize these interleaving features, with a negative polarity reflection arising from an interface of warm water overlying colder water. A seismic-derived sound speed image reveals the extent and lateral continuity of such interleaving layers. There is evidence of obliquely aligned internal waves emanating from the slope at 450–500 m. They follow the predicted trajectory of internal S2 tidal waves and can promote vertical mixing between Atlantic and Arctic-origin waters.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015JC011009
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Controlled-source electromagnetic and seismic delineation of sub-seafloor fluid flow structures in a gas hydrate province, offshore Norway (2016)
    Wiley
    In:  Geophysical Journal International, 206 (2). pp. 1093-1110.
    Details
    Publication Date: 2019-02-01
    Description: Deep sea pockmarks underlain by chimney-like or pipe structures that contain methane hydrate are abundant along the Norwegian continental margin. In such hydrate provinces the interaction between hydrate formation and fluid flow has significance for benthic ecosystems and possibly climate change. The Nyegga region, situated on the western Norwegian continental slope, is characterized by an extensive pockmark field known to accommodate substantial methane gas hydrate deposits. The aim of this study is to detect and delineate both the gas hydrate and free gas reservoirs at one of Nyegga's pockmarks. In 2012, a marine controlled-source electromagnetic (CSEM) survey was performed at a pockmark in this region, where high-resolution three-dimensional seismic data were previously collected in 2006. Two-dimensional CSEM inversions were computed using the data acquired by ocean bottom electrical field receivers. Our results, derived from unconstrained and seismically constrained CSEM inversions, suggest the presence of two distinctive resistivity anomalies beneath the pockmark: a shallow vertical anomaly at the underlying pipe structure, likely due to gas hydrate accumulation, and a laterally extensive anomaly attributed to a free gas zone below the base of the gas hydrate stability zone. This work contributes to a robust characterization of gas hydrate deposits within sub-seafloor fluid flow pipe structures.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/gji/ggw188
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Tectonic Controls on Gas Hydrate Distribution off SW Taiwan (2019)
    Wiley | AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 124 (2). pp. 1164-1184.
    Details
    Publication Date: 2022-01-31
    Description: The northern part of the South China Sea is characterized by widespread occurrence of bottom simulating reflectors (BSR) indicating the presence of marine gas hydrate. Because the area covers both a tectonically inactive passive margin and the termination of a subduction zone, the influence of tectonism on the dynamics of gas hydrate systems can be studied in this region. Geophysical data show that there are multiple thrust faults on the active margin while much fewer and smaller faults exist in the passive margin. This tectonic difference matches with a difference in the geophysical characteristics of the gas hydrate systems. High hydrate saturation derived from ocean bottom seismometer data and controlled source electromagnetic data and conspicuous high‐amplitude reflections in P‐Cable 3D seismic data above the BSR are found in the anticlinal ridges of the active margin. In contrast all geophysical evidence for the passive margin points to normal to low hydrate saturations. Geochemical analyses of gas samples collected at seep sites on the active margin show methane with heavy δ13C isotope composition, while gas collected at the passive margin shows light carbon isotope composition. Thus, we interpret the passive margin as a typical gas hydrate province fuelled by biogenic production of methane and the active margin gas hydrate system as a system that is fuelled not only by biogenic gas production but also by additional advection of thermogenic methane from the subduction system.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2018JB016213
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Polyphase magmatism during the formation of the northern East Greenland continental margin (2019)
    AGU (American Geophysical Union) | Wiley
    In:  Tectonics, 38 (8). pp. 2961-2982.
    Details
    Publication Date: 2022-01-31
    Description: New marine geophysical data acquired across the partly ice‐covered northern East Greenland continental margin highlight a complex interaction between tectonic and magmatic events. Breakup‐related lava flows are imaged in reflection seismic data as seaward dipping reflectors (SDRs), which are found to decrease in size both northwards and southwards from a central point at 75° N. We provide evidence that the magnetic anomaly pattern in the shelf area is related to volcanic phases and not to the presence of oceanic crust. The remnant magnetization of the individual lava flows is used to deduce a relative timing of the emplacement of the volcanic wedges. We find that the SDRs have been emplaced over a period of 2‐4 Ma progressively from north to south and from landward to seaward. The new data indicate a major post‐middle Eocene magmatic phase around the landward termination of the West Jan Mayen Fracture Zone. This post‐40 Ma volcanism likely was associated with the progressive separation of the Jan Mayen microcontinent from East Greenland. The break‐up of the Greenland Sea started at several isolated seafloor spreading cells whose location was controlled by rift structures and led to the present‐day segmentation of the margin. The original rift basins were subsequently connected by steady‐state seafloor spreading that propagated southwards, from the Greenland Fracture Zone to the Jan Mayen Fracture Zone. Key Points Polyphase Cenozoic volcanic rifting and consecutive emplacement of breakup‐related lava flows units along the northern East Greenland margin Breakup along restricted margin segments is followed by north to south directed progressive opening of the Greenland Sea Widespread post‐middle Eocene (〈 40 Ma) offshore magmatism, associated with the breakup of the Jan Mayen microcontinent from East Greenland
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2019TC005552
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    In Situ Temperature Measurements at the Svalbard Continental Margin: Implications for Gas Hydrate Dynamics (2018)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2022-03-09
    Description: During expedition MARIA S. MERIAN MSM57/2 to the Svalbard margin offshore Prins Karls Forland, the seafloor drill rig MARUM-MeBo70 was used to assess the landward termination of the gas hydrate system in water depths between 340 and 446 m. The study region shows abundant seafloor gas vents, clustered at a water depth of ~400 m. The sedimentary environment within the upper 100 meters below seafloor (mbsf) is dominated by ice-berg scours and glacial unconformities. Sediments cored included glacial diamictons and sheet-sands interbedded with mud. Seismic data show a bottom simulating reflector terminating ~30 km seaward in ~760 m water depth before it reaches the theoretical limit of the gas hydrate stability zone (GHSZ) at the drilling transect. We present results of the first in situ temperature measurements conducted with MeBo70 down to 28 mbsf. The data yield temperature gradients between ~38°C km-1 at the deepest site (446 m) and ~41°C km-1 at a shallower drill site (390 m). These data constrain combined with in situ pore-fluid data, sediment porosities, and thermal conductivities the dynamic evolution of the GHSZ during the past 70 years for which bottom water temperature records exist. Gas hydrate is not stable in the sediments at sites shallower than 390 m water depth at the time of acquisition (August 2016). Only at the drill site in 446 m water depth, favorable gas hydrate stability conditions are met (maximum vertical extent of ~60 mbsf); however, coring did not encounter any gas hydrates.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Pockmarks in the Witch Ground Basin, central North Sea (2019)
    Wiley | AGU (American Geophysical Union)
    Details
    Publication Date: 2024-01-29
    Description: Marine sediments host large amounts of methane (CH4), which is a potent greenhouse gas. Quantitative estimates for methane release from marine sediments are scarce, and a poorly constrained temporal variability leads to large uncertainties in methane emission scenarios. Here, we use 2D and 3D seismic reflection, multibeam bathymetric, geochemical and sedimentological data to (I) map and describe pockmarks in the Witch Ground Basin (central North Sea), (II) characterize associated sedimentological and fluid migration structures, and (III) analyze the related methane release. More than 1500 pockmarks of two distinct morphological classes spread over an area of 225 km2. The two classes form independently from another and are corresponding to at least two different sources of fluids. Class 1 pockmarks are large in size (〉 6 m deep, 〉 250 m long, and 〉 75 m wide), show active venting, and are located above vertical fluid conduits that hydraulically connect the seafloor with deep methane sources. Class 2 pockmarks, which comprise 99.5 % of all pockmarks, are smaller (0.9‐3.1 m deep, 26‐140 m long, and 14‐57 m wide) and are limited to the soft, fine‐grained sediments of the Witch Ground Formation and possibly sourced by compaction‐related dewatering. Buried pockmarks within the Witch Ground Formation document distinct phases of pockmark formation, likely triggered by external forces related to environmental changes after deglaciation. Thus, greenhouse gas emissions from pockmark fields cannot be based on pockmark numbers and present‐day fluxes but require an analysis of the pockmark forming processes through geological time.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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