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  • 1
    ISSN: 1437-3262
    Schlagwort(e): Benthic-pelagic coupling ; Greenland-Norwegian Sea ; Remineralization ; Bioturbation ; Sediment accumulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract The sedimentation pattern of organic material in the Greenland-Norwegian Sea is reflected in the surface sediments, although less than 0.5% of the organic matter is buried in the sediment. Maximum fluxes and benthic responses are observed during June and/or August/September, following the pattern of export production in the pelagial zone. The annual remineralization rate on the Vøring Plateau is 3.0 g C m−2 a −1 Freshly settled phytodetritus, as detected by chlorophyll measurements, is rapidly mixed into the sediment and decomposed. It stimulates the activity of benthic organisms, especially foraminifera. The mixing coefficient for this material is D b=0.2 cm2 d−1, which is two to three orders of magnitude higher than that estimated from radiotracer methods. The effect on the geological record, however, is likely to be small. Chlorophyll-containing particles are at first very evenly distributed on the seafloor. After partial decomposition and resuspension, a secondary redistribution of particles occurs which can result in the formation of a high accumulation area, with an up to 80-fold increase in the sedimentation rate by lateral advection. This is mainly due to physical processes, because biodeposition mediated by benthic animals increases sedimentation by only a factor of two or three.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-02-01
    Beschreibung: Atlantis II Deep, a submarine basin of the Red Sea, is noteworthy because of its hydrothermally active brine pools. High-resolution temperature records from Poseidon Cruise during February 2011 revealed small steps thermal staircase in the lower transition zone from ≈2002 to 2008/2009 m depth at stations. Four vertically well-mixed convective layers, lower convective layer (LCL) and upper convective layers (UCL1–3), separated by high-temperature gradients at the interfaces were observed. The temperature of the layers UCL1–3 has dropped between 2008 and 2011. The top of UCL3 extends to about 2008/2009 m at stations and its average thickness has increased from 3.3 ± 0.5 m in 1992 to 7 m in 2011, whereas the thickness of layers UCL1–2 has decreased from 25.2 ± 0.3 m to 19.8 m and from 16.4 ± 0.5 m to 14.7 m, respectively, during this time. The upward buoyancy flux is 0.032 to 0.038 × 10−7 m2 s−3 which gives migration speed of UCL3 layer from 0.1 to 0.12 m year−1. With this speed, the thermal staircase ≈6 m thick will merge with UCL3 in 50 to 60 years increasing the thickness from 7 m to nearly 13 m.
    Materialart: Article , PeerReviewed
    Format: text
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  • 3
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    Unbekannt
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1817-1829.
    Publikationsdatum: 2017-05-23
    Beschreibung: Seafloormethane emission from the Quepos Slide on the submarine segment of the Costa Rica fore-arc margin was estimated by extrapolating flux measurements from individual seeps to the total area covered by bacterial mats. This approach is based on the combination of detailed mapping to determine the abundance of seeps and the application of a numerical model to estimate the amount of benthic methane fluxes. Model results suggest that the majority of the studied seeps transport rather limited amount of methane (on average: *177 lmol cm-2 a-1) into the water column due to moderate upward advection, allowing for intense anaerobic oxidation of methane (AOM; on average: 53 % of the methane flux is consumed). Depth-integrated AOM rates (56–1,538 lmol CH4 cm-2 a-1) are comparable with values reported from other active seep sites. The overall amount of dissolved methane released into the water column from the entire area covered by bacterial mats on the Quepos Slide is estimated to be about 0.28 9 106 mol a-1. This conservative estimate which relies on rather accurate determinations of seafloor methane fluxes emphasizes the potential importance of submarine slides as sites of natural methane seepage; however, at present the global extent of methane seepage from submarine slides is largely unknown.
    Materialart: Article , PeerReviewed
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  • 4
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    Forschungszentrum Jülich GmbH
    In:  Journal of Large-Scale Research Facilities JLSRF, 3 (A117).
    Publikationsdatum: 2017-09-06
    Beschreibung: The remotely operated vehicle ROV KIEL 6000 is a deep diving platform rated for water depths of 6000 meters. It is linked to a surface vessel via an umbilical cable transmitting power (copper wires) and data (3 single-mode glass fibers). As standard it comes equipped with still and video cameras and two different manipulators providing eyes and hands in the deep. Besides this a set of other tools may be added depending on the mission tasks, ranging from simple manipulative tools such as chisels and shovels to electrically connected instruments which can send in-situ data to the ship through the ROVs network, allowing immediate decisions upon manipulation or sampling strategies.
    Materialart: Article , NonPeerReviewed
    Format: text
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  • 5
    Publikationsdatum: 2019-09-23
    Beschreibung: The central Chilean subduction zone between 35°S and 37°S was investigated in order to identify, document and possibly understand fluid flow and fluid venting within the forearc region. Several areas were mapped using multibeam bathymetry and backscatter, high-resolution sidescan sonar, chirp subbottom profiling and reflection seismic data. On a subsequent cruise ground-truthing observations were made using a video sled. In general, this dataset shows surprisingly little evidence of fluid venting along the mid-slope region, in contrast to other subduction zones such as Central America and New Zealand. There were abundant indications of active and predominantly fossil fluid venting along the upper slope between 36.5°S and 36.8°S at the seaward margin of an intraslope basin. Here, backscatter anomalies suggest widespread authigenic carbonate deposits, likely the result of methane-rich fluid expulsion. There is unpublished evidence that these fluids are of biogenic origin and generated within the slope sediments, similar to other accretionary margins but in contrast to the erosional margin off Central America, where fluids have geochemical signals indicating an origin from the subducting plate.
    Materialart: Article , PeerReviewed
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  • 6
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    Unbekannt
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1801-1815.
    Publikationsdatum: 2019-09-23
    Beschreibung: Methane (CH4) concentrations and CH4 stable carbon isotopic composition (d13CCH4 ) were investigated in the water column within Jaco Scar. It is one of several scars formed by massive slides resulting from the subduction of seamounts offshore Costa Rica, a process that can open up structural and stratigraphical pathways for migrating CH4. The release of large amounts of CH4 into the adjacent water column was discovered at the outcropping lowermost sedimentary sequence of the hanging wall in the northwest corner of Jaco Scar, where concentrations reached up to 1,500 nmol L-1. There CH4-rich fluids seeping from the sedimentary sequence stimulate both growth and activity of a dense chemosynthetic community. Additional point sources supplying CH4 at lower concentrations were identified in density layers above and below the main plume from light carbon isotope ratios. The injected CH4 is most likely a mixture of microbial and thermogenic CH4 as suggested by d13CCH4 values between -50 and -62 % Vienna Pee Dee Belemnite. This CH4 spreads along isopycnal surfaces throughout the whole area of the scar, and the concentrations decrease due to mixing with ocean water and microbial oxidation. The supply of CH4 appears to be persistent as repeatedly high CH4 concentrations were found within the scar over 6 years. The maximum CH4 concentration and average excess CH4 concentration at Jaco Scar indicate that CH4 seepage from scars might be as significant as seepage from other tectonic structures in the marine realm. Hence, taking into account the global abundance of scars, such structures might constitute a substantial, hitherto unconsidered contribution to natural CH4 sources at the seafloor.
    Materialart: Article , PeerReviewed
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  • 7
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    Forschungszentrum Jülich GmbH
    In:  [Paper] In: Statusseminar Meeresforschung mit FS Sonne 1999, 10.-12.03.1999, Freiberg, Germany . Meeresforschung mit FS Sonne ; pp. 229-230 .
    Publikationsdatum: 2020-05-28
    Materialart: Conference or Workshop Item , PeerReviewed
    Format: text
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  • 8
    facet.materialart.
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    Forschungszentrum Jülich GmbH
    In:  Journal of Large-Scale Research Facilities JLSRF, 2 (A79).
    Publikationsdatum: 2019-09-23
    Beschreibung: The Autonomous Underwater Vehicle (AUV) „ABYSS“ is a modular AUV designed to survey the ocean combining geophysical studies of the seafloor with oceanographic investigations of the overlying water column. The basic mission of ABYSS is deep-sea exploration, specifically in volcanically and tectonically active parts, such as mid-ocean ridges. With a maximum mission depth of 6000 meters, the AUV uses several technologies to map the seafloor accurately and determine its geological structure with applications from geology to biology to mineral exploration.
    Materialart: Article , NonPeerReviewed
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  • 9
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    Forschungszentrum Jülich GmbH
    In:  Journal of Large-Scale Research Facilities JLSRF, 3 (A118).
    Publikationsdatum: 2018-04-27
    Beschreibung: The remotely operated vehicle ROV PHOCA is a deep diving platform rated for water depths of 3000 meters. The ROV is linked to a surface vessel via an umbilical cable transmitting power (copper wires) and data (3 single-mode glass fibers). As standard it comes equipped with still and video cameras and two different manipulators providing eyes and hands in the deep. Special emphasis was put on the compatibility of numerous systems with the existing ROV KIEL 6000 to facilitate the use of both systems on various research vessels with a given team of ROV pilots. Besides this, a set of other tools may be added depending on the mission tasks, ranging from simple manipulative tools as chisels and shovels to electrically connected instruments which can send insitu data to the ship through the ROVs network, allowing immediate decisions upon manipulation or sampling strategies.
    Materialart: Article , NonPeerReviewed
    Format: text
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    Publikationsdatum: 2018-01-19
    Beschreibung: The Makran accretionary complex shows a distinct bottom-simulating reflector, indicating a thick gas-hydrate-bearing horizon between the deformational front and about 1350 m water depth which seals off the upward flow of gas-charged fluids. A field of presently inactive mud diapirs with elevations up to 65 m was discovered in the abyssal plain seawards of the deformation front, suggesting that in the past conditions were favorable for periodic but localized vigorous mud diapirism. Regional destabilization of the gas hydrate leading to focused flow was observed where deep-penetrating, active faults reach the base of the gas-hydrate layer, as in a deeply incised submarine canyon (2100–2500 m water depth). At this location we discovered seeps of methane and H2S-rich fluids associated with chemoautotrophic vent faunas (e.g., Calyptogena sp.). Driven by the accretionary wedge dynamics, the landward part of the gas-hydrate layer below the Makran margin is being progressively uplifted. Due to reduced hydrostatic pressure and rising ocean bottom-water temperatures, gas hydrates are progressively destabilized and dissociated into hydrate water, methane and H2S. Sediment temperatures lie outside the methane stability field wherever water depth is less than 800 m. Above this depth, upward migration of fluids to the seafloor is unimpeded, thus explaining the abundance of randomly distributed gas seeps observed at water depths of 350 to 800 m.
    Materialart: Article , PeerReviewed
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