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  • Kiel  (8)
  • Wiley  (5)
  • Berlin : Heinrich-Böll-Stiftung  (3)
  • ACS (American Chemical Society)  (2)
  • Frontiers  (1)
  • MIGRATE  (1)
  • Wissenschaftliche Auswertungen
  • 2015-2019  (20)
  • 11
    Online Resource
    Online Resource
    Entwicklung und Validierung einer Methodik zur Extraktion von Mikroplastikpartikeln aus Sedimenten (2017)
    Kiel
    Details Availability
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (85 Blatt = 2,6 MB) , Illustrationen, Diagramme, Karte
    URL: http://oceanrep.geomar.de/39540/
    Language: German
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 12
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    Shallow gas migration along hydrocarbon wells – An unconsidered, anthropogenic source of biogenic methane in the North Sea (2017)
    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 51 (17). pp. 10262-10268.
    Details
    Publication Date: 2020-02-06
    Description: Shallow gas migration along hydrocarbon wells constitutes a potential methane emission pathway that currently is not recognized in any regulatory framework or greenhouse gas inventory. Recently, the first methane emission measurements at three abandoned offshore wells in the Central North Sea (CNS) were conducted showing that considerable amounts of biogenic methane originating from shallow gas accumulations in the overburden of deep reservoirs were released by the boreholes. Here, we identify numerous wells poking through shallow gas pockets in 3D seismic data of the CNS indicating that about one third of the wells may leak, potentially releasing a total of 3-17 kt of methane per year into the North Sea. This poses a significant contribution to the North Sea methane budget. A large fraction of this gas (~42 %) may reach the atmosphere via direct bubble transport (0-2 kt yr-1) and via diffusive exchange of methane dissolving in the surface mixed layer (1-5 kt yr-1), as indicated by numerical modeling. In the North Sea and in other hydrocarbon-prolific provinces of the world shallow gas pockets are frequently observed in the sedimentary overburden and aggregate leakages along the numerous wells drilled in those areas may be significant.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    DOI: 10.1021/acs.est.7b02732
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 13
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    Towards a parameterization of global-scale organic carbon mineralization kinetics in surface marine sediments (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 29 . pp. 812-829.
    Details
    Publication Date: 2017-12-19
    Description: An empirical function is derived for predicting the rate-depth profile of particulate organic carbon (POC) degradation in surface marine sediments including the bioturbated layer. The rate takes the form of a power law analogous to the Middelburg function. The functional parameters were optimized by simulating measured benthic O2 and NO3− fluxes at 185 stations worldwide using a diagenetic model. The novelty of this work rests with the finding that the vertically-resolved POC degradation rate in the bioturbated zone can be determined using a simple function where the POC rain rate is the governing variable. Although imperfect, the model is able to fit 71 % of paired O2 and NO3− fluxes to within 50% of measured values. It further provides realistic geochemical concentration-depth profiles, NO3− penetration depths and apparent first-order POC mineralization rate constants. The model performs less well on the continental shelf due to the high heterogeneity there. When applied to globally resolved maps of rain rate, the model predicts a global denitrification rate of 182 ± 88 Tg yr−1 of N and a POC burial rate of 107 ± 52 Tg yr−1 of C with a mean carbon burial efficiency of 6.1%. These results are in very good agreement with published values. Our proposed function is conceptually simple, requires less parameterization than multi-G type models and is suitable for non-steady state applications. It provides a basis for more accurately simulating benthic nutrient fluxes and carbonate dissolution rates in Earth system models.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015GB005087
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
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    Marine gas hydrate technology: State of the art and future possibilities for Europe (2019)
    MIGRATE
    In:  COST Action ES 1405, WG2 report, 2019 . MIGRATE, III, 61 pp.
    Details
    Publication Date: 2019-09-23
    Type: Report , NonPeerReviewed
    Format: text
    DOI: 10.3289/MIGRATE_WG2.2019
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    OceanRep: Report - other report
  • 15
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    A revised global estimate of dissolved iron fluxes from marine sediments (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 29 (5). pp. 691-707.
    Details
    Publication Date: 2019-09-23
    Description: Literature data on benthic dissolved iron (DFe) fluxes (µmol m−2 d−1), bottom water oxygen concentrations (O2BW, μM), and sedimentary carbon oxidation rates (COX, mmol m−2 d−1) from water depths ranging from 80 to 3700 m were assembled. The data were analyzed with a diagenetic iron model to derive an empirical function for predicting benthic DFe fluxes: inline image where γ (= 170 µmol m−2 d−1) is the maximum flux for sediments at steady state located away from river mouths. This simple function unifies previous observations that COX and O2BW are important controls on DFe fluxes. Upscaling predicts a global DFe flux from continental margin sediments of 109 ± 55 Gmol yr−1, of which 72 Gmol yr−1 is contributed by the shelf (〈200 m) and 37 Gmol yr−1 by slope sediments (200–2000 m). The predicted deep-sea flux (〉2000 m) of 41 ± 21 Gmol yr−1 is unsupported by empirical data. Previous estimates of benthic DFe fluxes derived using global iron models are far lower (approximately 10–30 Gmol yr−1). This can be attributed to (i) inadequate treatment of the role of oxygen on benthic DFe fluxes and (ii) improper consideration of continental shelf processes due to coarse spatial resolution. Globally averaged DFe concentrations in surface waters simulated with the intermediate-complexity University of Victoria Earth System Climate Model were a factor of 2 higher with the new function. We conclude that (i) the DFe flux from marginal sediments has been underestimated in the marine iron cycle and (ii) iron scavenging in the water column is more intense than currently presumed.
    Type: Article , PeerReviewed
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    DOI: 10.1002/2014GB005017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 16
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    3-D basin-scale reconstruction of natural gas hydrate system of the Green Canyon, Gulf of Mexico (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 18 (5). pp. 1959-1985.
    Details
    Publication Date: 2020-02-06
    Description: Our study presents a basin-scale 3D modeling solution, quantifying and exploring gas hydrate accumulations in the marine environment around the Green Canyon (GC955) area, Gulf of Mexico. It is the first modeling study that considers the full complexity of gas hydrate formation in a natural geological system. Overall, it comprises a comprehensive basin re-construction, accounting for depositional and transient thermal history of the basin, source rock maturation, petroleum components generation, expulsion and migration, salt tectonics and associated multi-stage fault development. The resulting 3D gas hydrate distribution in the Green Canyon area is consistent with independent borehole observations. An important mechanism identified in this study and leading to high gas hydrate saturation (〉 80 vol. %) at the base of the gas hydrate stability zone (GHSZ), is the recycling of gas hydrate and free gas enhanced by high Neogene sedimentation rates in the region. Our model predicts the rapid development of secondary intra-salt mini-basins situated on top of the allochthonous salt deposits which leads to significant sediment subsidence and an ensuing dislocation of the lower GHSZ boundary. Consequently, large amounts of gas hydrates located in the deepest parts of the basin dissociate and the released free methane gas migrates upwards to recharge the GHSZ. In total, we have predicted the gas hydrate budget for the Green Canyon area that amounts to ∼3,256 Mt of gas hydrate which is equivalent to ∼340 Mt of carbon (∼7 x 1011 m3 of CH4 at STP conditions), and consists mostly of biogenic hydrates.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2017GC006876
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 17
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    Strong and Dynamic Benthic-Pelagic Coupling and Feedbacks in a Coastal Upwelling System (Peruvian Shelf) (2017)
    Frontiers
    In:  Frontiers in Marine Science, 4 (29).
    Details
    Publication Date: 2020-02-06
    Description: Monthly time-series data (1998–2009) of bottom water oxygen, nitrate and nitrite concentrations from the outer shelf (150 m water depth) in the oxygen minimum zone offshore Peru were coupled to a layered biogeochemical sediment model to investigate benthic-pelagic coupling over multi-annual time scales. The model includes the mineralization of four reactive pools of particulate organic carbon (POC) with lifetimes of 0.13, 1.3, 20, and 1700 year that were constrained using empirical data. Total POC rain rates to the seafloor were derived from satellite based estimates of primary production. Solute fluxes and concentrations in sediment porewater showed highly dynamic behavior over the course of a typical year. Conversion of fixed N to N2 by denitrification varied from 1.1 mmol m−2 d−1 of N in winter to 1.8 mmol m−2 d−1 of N in summer with a long term mean N loss for the shelf of 1.5 mmol m−2 d−1 of N. Fixed N loss across the whole time-series agreed very well with a previously-published vertically-integrated sediment model for coupling the benthic and pelagic N cycle in regional and global models. Dissimilatory nitrate reduction to ammonium (DNRA) emerges as a major process in the benthic N cycle, producing on average 1.9 mmol m−2 d−1 of ammonium: more than twice the rate of ammonification of organic nitrogen. The model predicts sulfide emissions from the sediment of up to 1 mmol m−2 d−1 when POC rain rate exceeds 20 mmol m−2 d−1, in agreement with past observations of benthic sulfide fluxes and sulfide plume distributions in the water column. This study demonstrates that sediments on the Peruvian shelf are not static repositories that are independent of changes taking place in the water column. Our results strongly suggest the shelf sediments must exert an important feedback on biogeochemical processes in the overlying waters, and should be considered in regional model studies.
    Type: Article , PeerReviewed
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    DOI: 10.3389/fmars.2017.00029
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 18
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    Simulating and Quantifying Multiple Natural Subsea CO2 Seeps at Panarea Island (Aeolian Islands, Italy) as a Proxy for Potential Leakage from Subseabed Carbon Storage Sites (2019)
    ACS (American Chemical Society)
    In:  Environmental Science & Technology, 53 (17). pp. 10258-10268.
    Details
    Publication Date: 2022-01-31
    Description: Carbon dioxide (CO2) capture and storage (CCS) has been discussed as a potentially significant mitigation option for the ongoing climate warming. Natural CO2 release sites serve as natural laboratories to study subsea CO2 leakage in order to identify suitable analytical methods and numerical models to develop best-practice procedures for the monitoring of subseabed storage sites. We present a new model of bubble (plume) dynamics, advection-dispersion of dissolved CO2, and carbonate chemistry. The focus is on a medium-sized CO2 release from 294 identified small point sources around Panarea Island (South-East Tyrrhenian Sea, Aeolian Islands, Italy) in water depths of about 40–50 m. This study evaluates how multiple CO2 seep sites generate a temporally variable plume of dissolved CO2. The model also allows the overall flow rate of CO2 to be estimated based on field measurements of pH. Simulations indicate a release of ∼6900 t y–1 of CO2 for the investigated area and highlight an important role of seeps located at 〉20 m water depth in the carbon budget of the Panarea offshore gas release system. This new transport-reaction model provides a framework for understanding potential future leaks from CO2 storage sites.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    DOI: 10.1021/acs.est.9b02131
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 19
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    Origin of high Mg and SO 4 fluids in sediments of the Terceira Rift, Azores – indications for caminite dissolution in a waning hydrothermal system (2019)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 20 .
    Details
    Publication Date: 2022-01-31
    Description: During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyper‐slow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2800 m water depth show an anomalous composition with Mg, SO4, and total alkalinity (TA) concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25Mg(OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite, and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection towards the seafloor.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2019GC008525
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 20
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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
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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