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  • 2010-2014  (2)
  • 2000-2004  (70)
  • 2014  (2)
  • 2000  (70)
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  • 2010-2014  (2)
  • 2000-2004  (70)
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  • 1
    Online Resource
    Online Resource
    Untersuchungen zum regionalen Verteilungsmuster benthischer Stoffflüsse unter Berücksichtigung biogeographischer Provinzen im Arabischen Meer und im Atlantik (2000)
    Kiel
    Details Availability
    Keywords: Dissertation ; Hochschulschrift ; Atlantischer Ozean Nordost ; Abyssal ; Benthos ; Meeressediment ; Frühdiagenese ; Arabisches Meer
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 202Seiten = 25MB) , graph. Darst
    URL: https://oceanrep.geomar.de/id/eprint/48016/
    Language: German
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  • 2
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    Pore-water distribution and quantification of diffusive benthic fluxes of silicic acid, nitrate and phosphate in surface sediments of the deep Arabian Sea (2000)
    Pergamon Press
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 47 (14). pp. 2707-2734.
    Details
    Publication Date: 2020-08-05
    Description: Benthic fluxes and pore-water compositions of silicic acid, nitrate and phosphate were investigated for surface sediments of the abyssal Arabian Sea during four cruises (1995-1998). Five sites located in the northern (NAST), western (WAST), central (CAST), eastern (EAST), and southern (SAST) Arabian Sea were revisited during intermonsoonal periods after the NE- and SW-Monsoon. At these sites, benthic fluxes of remineralized nutrients from the sediment to the bottom water of 36-106, 102-350 and 4-16 mmol m-2 yr-1 were measured for nitrate, silicic acid and phosphate, respectively. The benthic fluxes and pore-water compositions showed a distinct regional pattern. Highest fluxes were observed in the western and northern region of the Arabian Sea, whereas decreasing fluxes were derived towards the southeast. At WAST, the general temporal pattern of primary production, related to the NE- and SW-Monsoon, is reflected by benthic fluxes. In contrast, at sites NAST, SAST, CAST, and EAST a temporal pattern of fluxes in response to the monsoon is not obvious. Our results reveal a clear coupling between the general regional pattern of production in surface waters and the response of the benthic environment, as indicated by the flux of remineralized nutrients, though a spatially differing degree of decoupling during transport and remineralization of particulate organic matter and biogenic opal was observed. This has to be taken into account regarding budget calculations and paleoceanographic topics.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/s0967-0645(00)00046-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    A water column study of methane around gas flares located at the West Spitsbergen continental margin (2014)
    Elsevier
    In:  Continental Shelf Research, 72 . pp. 107-118.
    Details
    Publication Date: 2016-09-21
    Description: In the Arctic Seas, the West Spitsbergen continental margin represents a prominent methane seep area. In this area, free gas formation and gas ebullition as a consequence of hydrate dissociation due to global warming are currently under debate. Recent studies revealed shallow gas accumulation and ebullition of methane into the water column at more than 250 sites in an area of 665 km2. We conducted a detailed study of a subregion of this area, which covers an active gas ebullition area of 175 km2 characterized by 10 gas flares reaching from the seafloor at~245 m up to 50 m water depth to identify the fate of the released gas due to dissolution of methane from gas bubbles and subsequent mixing, transport and microbial oxidation. The oceanographic data indicated a salinity-controlled pycnocline situated ~20 m above the seafloor. A high resolution sampling program at the pycnocline at the active gas ebullition flare area revealed that the methane concentration gradient is strongly controlled by the pycnocline. While high methane concentrations of up to 524 nmol L−1 were measured below the pycnocline, low methane concentrations of less than 20 nmol L−1 were observed in the water column above. Variations in the δ13CCH4 values point to a 13C depleted methane source (~−60‰ VPDB) being mainly mixed with a background values of the ambient water (~−37.5‰ VPDB). A gas bubble dissolution model indicates that ~80% of the methane released from gas bubbles into the ambient water takes place below the pycnocline. This dissolved methane will be laterally transported with the current northwards and most likely microbially oxidized in between 50 and 100 days, since microbial CH4 oxidation rates of 0.78 nmol d−1 were measured. Above the pycnocline, methane concentrations decrease to local background concentration of ~10 nmol L−1. Our results suggest that the methane dissolved from gas bubbles is efficiently trapped below the pycnocline and thus limits the methane concentration in surface water and the air–sea exchange during summer stratification. During winter the lateral stratification breaks down and fractions of the bottom water enriched in methane may be vertically mixed and thus be potentially an additional source for atmospheric methane.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.csr.2013.07.013
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Seasonal variations of bioirrigation in coastal sediments: Modelling of field data (2000)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 64 (5). pp. 821-834.
    Details
    Publication Date: 2019-09-23
    Description: In near-shore and coastal margin sediments remineralization of organic carbon is significantly affected by biologically mediated solute exchange caused by burrow-dwelling infauna. Although irrigation rates have been determined for various environments, little is known about their seasonal variations and their coupling to the food-supply or the oxygen level in bottom waters. These aspects have been investigated at two sites in the Kiel Bight by modelling pore water concentrations of Cl, which is a suitable tracer for transport processes. A very similar temporal pattern of irrigation was determined at both sites. In spring and fall the effect of bioirrigation on the pore water concentration of Cl is important at both sites, and a more than two to five fold enhancement of solute exchange, relative to diffusional transport, was calculated. The temporal pattern of bioirrigation correlates with that of the Chl.-a (eq) inventory of the surface sediments. Enhanced irrigation rates follow the settling of plankton blooms in this region. During the summer, when low oxygen levels were observed in bottom waters, overall irrigation rates are low. Furthermore, the relative importance of irrigation processes operating close to the sediment surface increases suggesting an upward movement and migration of burrow-dwelling organisms in response to low O2-concentrations. Because bioirrigation is an important transport process coupling organic carbon flux, remineralization at the seafloor, and redox zonation in the sediment quantifying the seasonal cycle of the irrigation intensity represents a step forward in the dynamic understanding of benthic processes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0016-7037(99)00375-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Numerical Simulation of Water-Gas Flow and Transport Processes in Coastal Aquifers (2000)
    In:  EPIC3In: Sato, K. & Iwasa, Y. (eds) Groundwater Updates: New Science and Technology for Sustainable Groundwater Environment, Proceedings of the International Symposium on Groundwater, IAHR, 8.-10.5.2000, Sonic City, Japan., Springer-Verlag, Tokyo, Berlin, New, ISBN: 4 431 70283 0
    Details
    Publication Date: 2019-07-17
    Description: ABSTRACT:In this paper a twophase / threecomponent model concept for simulating interactionprocesses of fresh water, salt water, and methane in coastal aquifers is presented. The numericalalgorithm which is part of the simulator MUFTEUG is briefly explained. If methane occursin very low concentrations and builds no gas phase, the model concept is simplified to onephase/ three component. For this case a reasonable agreement of computations and measurements wasobtained in the range of available data. The simulations showed that certain concentration profilescan be caused by hydraulic conditions and not only by reaction processes as supposed before. Ifmethane occurs as a gas phase, it has a significant influence on the results.KEYWORDS: watergas flow, methane migration, multiphase / multicomponent model
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 6
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    Spatial budget of organic carbon flux to the seafloor of the northern North Atlantic (60°N-80°N) (2000)
    In:  EPIC3Global Biogeochemical Cycles, 14, pp. 329-340
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Pore-water distribution and quantification of diffusive benthic fluxes of silicic acid, nitrate and phosphate in surface sediments of the deep Arabian Sea (2000)
    In:  EPIC3Deep-sea research, 47, pp. 2707-2734
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    Methane venting associated with submarine groundwater discharge in Eckernförde Bucht, Baltic sea (2000)
    In:  EPIC3Proceedings of the 6th International Conference on Gas in Marine Sediments; 5.-9. 9. 2000; St. Petersburg, Russia
    Details
    Publication Date: 2019-07-17
    Description: Abstract:Submarine groundwater discharges are responsible for pockmark depressions on the bed ofEckernförde Bucht, Western Baltic. In these depressions there is an interface between almostfluid sediment and sea water that is typically about 1.5 2m below the surrounding seabed.Transects, made with a underwater digital video camera sled in October 1998 and September1999, showed that near the rims of the depressions the clay aquaclude was not covered byrecent methane generating organic sediment. Cracks could be seen in the clay indicating thatedges of the aquaclude layer are slowly collapsing into the steep sided depressions. Somesharply angular cobble sized clay clasts were seen just outside the pockmark rims suggestingthat blow-outs may occur. Acoustic turbidity is widespread in the sediments of the deeperparts of Eckernförde Bucht due to methane gas bubble formation within the sediment. Themethane seems to derive mainly from the decomposition of recent organic matter. Becausethe Bucht forms an cast facing funnel, near bed compensatory flows for the prevailingwesterly wind driven surface drift, seem to bring in phyto-detritus and faecal pellets whichdeposit and decay. Methane bubble release, gas escape holes with sediment and bacterial matswere widely observed through the Bucht in late summer and minor sediment disturbancecaused by, for example, crab tracks show that sulphidic sediment lies at best only a fewmillimetres below the surface in the deeper parts of the Bucht. Methane release wasparticularly prevalent towards the edge of the pockmarks and the release of free gas could beestimated from the density of recent bubble release holes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 9
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    Biogenic silica cycle in surface sediments of the Greenland Sea. (2000)
    In:  EPIC3Journal of Marine Systems, 23, pp. 333-342
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    Spatial budget of organic carbon flux to the seafloor of the northern North Atlantic (60°N-80°N) (2000)
    In:  EPIC3Global Biogeochemical Cycles, 14.., 329
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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