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    Glacigenic sedimentation pulses triggered post-glacial gas hydrate dissociation (2018)
    Nature Research
    In:  Nature Communications, 9 (Article number 635).
    Details
    Publication Date: 2021-02-08
    Description: Large amounts of methane are stored in continental margins as gas hydrates. They are stable under high pressure and low temperature, but react sensitively to environmental changes. Bottom water temperature and sea level changes were considered as main contributors to gas hydrate dynamics after the last glaciation. However, here we show with numerical simulations that pulses of increased sedimentation dominantly controlled hydrate stability during the end of the last glaciation offshore mid-Norway. Sedimentation pulses triggered widespread gas hydrate dissociation and explains the formation of ubiquitous blowout pipes in water depths of 600 to 800 m. Maximum gas hydrate dissociation correlates spatially and temporally with the formation or reactivation of pockmarks, which is constrained by radiocarbon dating of Isorropodon nyeggaensis bivalve shells. Our results highlight that rapid changes of sedimentation can have a strong impact on gas hydrate systems affecting fluid flow and gas seepage activity, slope stability and the carbon cycle.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1038/s41467-018-03043-z
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Submarine slope failures due to pipe structure formation (2018)
    Nature Research
    In:  Nature Communications, 9 (Art.No. 715).
    Details
    Publication Date: 2021-03-19
    Description: There is a strong spatial correlation between submarine slope failures and the occurrence of gas hydrates. This has been attributed to the dynamic nature of gas hydrate systems and the potential reduction of slope stability due to bottom water warming or sea level drop. However, 30 years of research into this process found no solid supporting evidence. Here we present new reflection seismic data from the Arctic Ocean and numerical modelling results supporting a different link between hydrates and slope stability. Hydrates reduce sediment permeability and cause build-up of overpressure at the base of the gas hydrate stability zone. Resulting hydro-fracturing forms pipe structures as pathways for overpressured fluids to migrate upward. Where these pipe structures reach shallow permeable beds, this overpressure transfers laterally and destabilises the slope. This process reconciles the spatial correlation of submarine landslides and gas hydrate, and it is independent of environmental change and water depth.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/s41467-018-03176-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming (2018)
    Nature Research
    In:  Nature Communications, 9 (Article number: 83 ).
    Details
    Publication Date: 2021-03-19
    Description: 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 the rate of isostatic uplift outpaced eustatic sea-level rise. The resultant local shallowing and lowering of hydrostatic pressure forced gas hydrate dissociation and dissolved chloride depletions consistent with our geochemical analysis. Hence, we propose that hydrate dissociation was triggered by postglacial isostatic rebound rather than anthropogenic warming. Furthermore, we show that methane fluxes from dissociating hydrates were considerably smaller than present methane seepage rates implying that gas hydrates were not a major source of methane to the oceans, but rather acted as a dynamic seal, regulating methane release from deep geological reservoirs.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1038/s41467-017-02550-9
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Could offshore groundwater rescue coastal cities? (2019)
    Nature Research
    In:  Nature, 574 (7776). p. 36.
    Details
    Publication Date: 2020-01-09
    Type: Article , NonPeerReviewed
    Format: text
    DOI: 10.1038/d41586-019-02924-7
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    OceanRep: Article in a Scientific Journal - without review
  • 5
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    Late Eocene onset of the Proto-Antarctic Circumpolar Current (2019)
    Nature Research
    In:  Scientific Reports, 9 (Article number: 10125).
    Details
    Publication Date: 2022-01-31
    Description: The formation of the Antarctic Circumpolar Current (ACC) is critical for the evolution of the global climate, but the timing of its onset is not well constrained. Here, we present new seismic evidence of widespread Late Eocene to Oligocene marine diagenetic chert in sedimentary drift deposits east of New Zealand indicating prolonged periods of blooms of siliceous microorganisms starting ~36 million years ago (Ma). These major blooms reflect the initiation of the arrival and upwelling of northern-sourced, nutrient-rich deep equatorial Pacific waters at the high latitudes of the South Pacific. We show that this change in circulation was linked to the initiation of a proto-ACC, which occurred ~6 Ma earlier than the currently estimated onset of the ACC at 30 Ma. We propose that the associated increased primary productivity and carbon burial facilitated atmospheric carbon dioxide reduction contributing to the expansion of Antarctic Ice Sheet at the Eocene-Oligocene Transition.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1038/s41598-019-46253-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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