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  • PANGAEA  (163)
  • [Bremen] : [Atlas Elektronik GmbH]  (1)
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  • 1
    Online Resource
    Online Resource
    IMGAM - Intelligentes Monitoring von klimaschädlichen CO2/CH4 Gasaustritten im Meer (2017)
    [Bremen] : [Atlas Elektronik GmbH]
    Details Availability
    Keywords: Forschungsbericht ; Meeresboden ; Gasemission ; Emissionsüberwachung
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (12 Seiten, 371,05 KB) , Illustrationen
    URL: https://doi.org/10.2314/GBV:1014659035
    DOI: 10.2314/GBV:1014659035
    Language: German
    Note: Förderkennzeichen BMBF 03SX346A-B. - Verbund-Nummer 01134086 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
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  • 2
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    Methane fluxes and carbonate deposits at eastern Mediterranean cold seeps (2013)
    PANGAEA
    In:  Supplement to: Römer, Miriam; Sahling, Heiko; Pape, Thomas; dos Santos Ferreira, Christian; Wenzhöfer, Frank; Boetius, Antje; Bohrmann, Gerhard (2013): Methane fluxes and carbonate deposits at a cold seep area of the Central Nile Deep Sea Fan, Eastern Mediterranean Sea. Marine Geology, 27-42, https://doi.org/10.1016/j.margeo.2013.10.011
    Details
    Publication Date: 2023-03-03
    Description: High acoustic seafloor-backscatter signals characterize hundreds of patches of methane-derived authigenic carbonates and chemosynthetic communities associated with hydrocarbon seepage on the Nile Deep Sea Fan (NDSF) in the Eastern Mediterranean Sea. During a high-resolution ship-based multibeam survey covering a ~ 225 km**2 large seafloor area in the Central Province of the NDSF we identified 163 high-backscatter patches at water depths between 1500 and 1800 m, and investigated the source, composition, turnover, flux and fate of emitted hydrocarbons. Systematic Parasound single beam echosounder surveys of the water column showed hydroacoustic anomalies (flares), indicative of gas bubble streams, above 8% of the high-backscatter patches. In echosounder records flares disappeared in the water column close to the upper limit of the gas hydrate stability zone located at about 1350 m water depth due to decomposition of gas hydrate skins and subsequent gas dissolution. Visual inspection of three high-backscatter patches demonstrated that sediment cementation has led to the formation of continuous flat pavements of authigenic carbonates typically 100 to 300 m in diameter. Volume estimates, considering results from high-resolution autonomous underwater vehicle (AUV)-based multibeam mapping, were used to calculate the amount of carbonate-bound carbon stored in these slabs. Additionally, the flux of methane bubbles emitted at one high-backscatter patch was estimated (0.23 to 2.3 × 10**6 mol a**-1) by combined AUV flare mapping with visual observations by remotely operated vehicle (ROV). Another high-backscatter patch characterized by single carbonate pieces, which were widely distributed and interspaced with sediments inhabited by thiotrophic, chemosynthetic organisms, was investigated using in situ measurements with a benthic chamber and ex situ sediment core incubation and allowed for estimates of the methane consumption (0.1 to 1 × 10**6 mol a**-1) and dissolved methane flux (2 to 48 × 10**6 mol a**-1). Our comparison of dissolved and gaseous methane fluxes as well as methane-derived carbonate reservoirs demonstrates the need for quantitative assessment of these different methane escape routes and their interaction with the geo-, bio-, and hydrosphere at cold seeps.
    Keywords: Center for Marine Environmental Sciences; HERMIONE; Hotspot Ecosystem Research and Mans Impact On European Seas; MARUM
    Type: Dataset
    Format: application/zip, 4 datasets
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    DATA PANGAEA
  • 3
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    Temperature, chloride and sulfate measurements of samples from RV METEOR cruise M112 (2017)
    PANGAEA
    In:  Supplement to: Loher, Markus; Pape, Thomas; Marcon, Yann; Römer, Miriam; Wintersteller, Paul; Praeg, Daniel; Torres, Marta E; Sahling, Heiko; Bohrmann, Gerhard (2018): Mud extrusion and ring-fault gas seepage – upward branching fluid discharge at a deep-sea mud volcano. Scientific Reports, 8, 6275, https://doi.org/10.1038/s41598-018-24689-1
    Details
    Publication Date: 2023-03-03
    Description: Submarine mud volcanoes release sediments and gas-rich fluids at the seafloor via deeply-rooted plumbing systems that remain poorly understood. Here the functioning of Venere mud volcano, on the Calabrian accretionary prism in ~1,600 m water depth is investigated, based on multi-parameter hydroacoustic and visual seafloor data obtained using ship-borne methods, ROVs, and AUVs. Two seepage domains are recognized: mud breccia extrusion from a summit, and hydrocarbon venting from peripheral sites, hosting chemosynthetic ecosystems and authigenic carbonates indicative of long-term seepage. Pore fluids in freshly extruded mud breccia (up to 13 °C warmer than background sediments) contained methane concentrations exceeding saturation by 2.7 times and chloride concentrations up to five times lower than ambient seawater. Gas analyses indicate an underlying thermogenic hydrocarbon source with potential admixture of microbial methane during migration along ring faults to the peripheral sites. The gas and pore water analyses point to fluids sourced deep (〉3 km) below Venere mud volcano. An upward-branching plumbing system is proposed to account for co-existing mud breccia extrusion and gas seepage via multiple surface vents that influence the distribution of seafloor ecosystems. This model of mud volcanism implies that methane-rich fluids may be released during prolonged phases of moderate activity.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 26 datasets
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    DATA PANGAEA
  • 4
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    Profiles of sediment echo soundings during three expeditions (M72/3, M84/2, and MSM15/2) in the Black Sea with links to Parasound data files (2012)
    PANGAEA
    In:  Supplement to: Römer, Miriam; Sahling, Heiko; Pape, Thomas; Bahr, André; Feseker, Tomas; Wintersteller, Paul; Bohrmann, Gerhard (2012): Geological control and magnitude of methane ebullition from a high-flux seep area in the Black Sea - the Kerch seep area. Marine Geology, 319, 57-74, https://doi.org/10.1016/j.margeo.2012.07.005
    Details
    Publication Date: 2023-05-12
    Description: We investigated gas bubble emissions at the Don-Kuban paleo-fan in the northeastern Black Sea regarding their geological setting, quantities as well as spatial and temporal variabilities during three ship expeditions between 2007 and 2011. About 600 bubble-induced hydroacoustic anomalies in the water column (flares) originating from the seafloor above the gas hydrate stability zone (GHSZ) at ~700 m water depth were found. At about 890 m water depth a hydrocarbon seep area named "Kerch seep area" was newly discovered within the GHSZ. We propose locally domed sediments ('mounds') discovered during ultra-high resolution bathymetric mapping with an autonomous underwater vehicle (AUV) to result from gas hydrate accumulation at shallow depths. In situ measurements indicated spatially limited temperature elevations in the shallow sediment likely induced by upward fluid flow which may confine the local GHSZ to a few meters below the seafloor. As a result, gas bubbles are suspected to migrate into near-surface sediments and to escape the seafloor through small-scale faults. Hydroacoustic surveys revealed that several flares originated from a seafloor area of about 1 km**2 in size. The highest flare disappeared in about 350 m water depth, suggesting that the released methane remains in the water column. A methane flux estimate, combining data from visual quantifications during dives with a remotely operated vehicle (ROV) with results from ship-based hydroacoustic surveys and gas analysis revealed that between 2 and 87 x 10**6 mol CH4 yr-1 escaped into the water column above the Kerch seep area. Our results show that the finding of the Kerch seep area represents a so far underestimated type of hydrocarbon seep, which has to be considered in methane budget calculations.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 5
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    Methane concentrations in the central North Sea (2015)
    PANGAEA
    In:  Supplement to: Mau, Susan; Gentz, Torben; Körber, Jan-Hendrik; Torres, Marta E; Römer, Miriam; Sahling, Heiko; Wintersteller, Paul; Martinez, Roi; Schlüter, Michael; Helmke, Elisabeth (2015): Seasonal methane accumulation and release from a gas emission site in the central North Sea. Biogeosciences, 12(18), 5261-5276, https://doi.org/10.5194/bg-12-5261-2015
    Details
    Publication Date: 2023-04-22
    Description: We investigated dissolved methane distributions along a 6 km transect crossing active seep sites at 40 m water depth in the central North Sea. These investigations were done under conditions of thermal stratification in summer (July 2013) and homogenous water column in winter (January 2014). Dissolved methane accumulated below the seasonal thermocline in summer with a median concentration of 390 nM, whereas during winter, methane concentrations were typically much lower (median concentration of 22 nM). High-resolution methane analysis using an underwater mass-spectrometer confirmed our summer results and was used to document prevailing stratification over the tidal cycle. We contrast estimates of methane oxidation rates (from 0.1 to 4.0 nM day**-1) using the traditional approach scaled to methane concentrations with microbial turnover time values and suggest that the scaling to concentration may obscure the ecosystem microbial activity when comparing systems with different methane concentrations. Our measured and averaged rate constants (k') were on the order of 0.01 day**-1, equivalent to a turnover time of 100 days, even when summer stratification led to enhanced methane concentrations in the bottom water. Consistent with these observations, we could not detect known methanotrophs and pmoA genes in water samples collected during both seasons. Estimated methane fluxes indicate that horizontal transport is the dominant process dispersing the methane plume. During periods of high wind speed (winter), more methane is lost to the atmosphere than oxidized in the water. Microbial oxidation seems of minor importance throughout the year.
    Keywords: AWI_PhyOce; Center for Marine Environmental Sciences; MARUM; Physical Oceanography @ AWI
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 6
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    Physical oceanography, pore water chemistry and water column methane turover rates during POLARSTERN cruise ANT-XXIX/4 (2016)
    PANGAEA
    In:  Supplement to: Geprägs, Patrizia; Torres, Marta E; Mau, Susan; Kasten, Sabine; Römer, Miriam; Bohrmann, Gerhard (2016): Carbon cycling fed by methane seepage at the shallow Cumberland Bay, South Georgia, sub-Antarctic. Geochemistry, Geophysics, Geosystems, 17(4), 1401-1418, https://doi.org/10.1002/2016GC006276
    Details
    Publication Date: 2023-01-13
    Description: Recent studies have suggested that the marine contribution of methane from shallow regions and melting marine terminating glaciers may have been underestimated. Here we report on methane sources and potential sinks associated with methane seeps in Cumberland Bay, South Georgia's largest fjord system. The average organic carbon content in the upper 8 meters of the sediment is around 0.65 wt.%; this observation combined with Parasound data suggest that the methane gas accumulations probably originate from peat-bearing sediments currently located several tens of meters below the seafloor. Only one of our cores indicates upward advection; instead most of the methane is transported via diffusion. Sulfate and methane flux estimates indicate that a large fraction of methane is consumed by anaerobic oxidation of methane (AOM). Carbon cycling at the sulfate-methane transition (SMT) results in a marked fractionation of the d13C-CH4 from an estimated source value of -65 per mil to a value as low as -96 per mil just below the SMT. Methane concentrations in sediments are high, especially close to the seepage sites (~40 mM); however, concentrations in the water column are relatively low (max. 58 nM) and can be observed only close to the seafloor. Methane is trapped in the lowermost water mass, however, measured microbial oxidation rates reveal very low activity with an average turnover of 3.1 years. We therefore infer that methane must be transported out of the bay in the bottom water layer. A mean sea-air flux of only 0.005 nM/m²/s confirms that almost no methane reaches the atmosphere.
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 7
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    (Table 2) Volume estimation of the carbonate slabs distributed in an area of about 1.4 km2 and estimate of carbonate-bound carbon stored within the patches (2013)
    PANGAEA
    Details
    Publication Date: 2023-03-03
    Keywords: Area; Calcium carbonate, mass; Calcium carbonate, volume; Carbon; C-area; Center for Marine Environmental Sciences; Diameter; Height; MARUM; MULT; Multiple investigations; Sample code/label; Shape; Volume
    Type: Dataset
    Format: text/tab-separated-values, 133 data points
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    DATA PANGAEA
  • 8
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    Active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia (2014)
    PANGAEA
    In:  Supplement to: Römer, Miriam; Torres, Marta E; Kasten, Sabine; Kuhn, Gerhard; Graham, Alastair G C; Mau, Susan; Little, Crispin T S; Linse, Katrin; Pape, Thomas; Geprägs, Patrizia; Fischer, David; Wintersteller, Paul; Marcon, Yann; Rethemeyer, Janet; Bohrmann, Gerhard; Shipboard scientific party ANT-XXIX/4 (2014): First evidence of widespread active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia. Earth and Planetary Science Letters, 403, 166-177, https://doi.org/10.1016/j.epsl.2014.06.036
    Details
    Publication Date: 2023-03-16
    Description: An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.
    Keywords: AWI_Paleo; Center for Marine Environmental Sciences; MARUM; Paleoenvironmental Reconstructions from Marine Sediments @ AWI
    Type: Dataset
    Format: application/zip, 5 datasets
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    DATA PANGAEA
  • 9
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    Underwater mass spectrometry (UWMS) methane concentrations in the central North Sea (2015)
    PANGAEA
    Details
    Publication Date: 2023-04-22
    Keywords: Center for Marine Environmental Sciences; Counts; DEPTH, water; MARUM; Methane
    Type: Dataset
    Format: text/tab-separated-values, 35 data points
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    DATA PANGAEA
  • 10
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    Heat flows and chemical composition of volcanic samples from Henry Seamount, Meteor cruise M146 (2020)
    PANGAEA
    Details
    Publication Date: 2023-09-01
    Description: Our knowledge of venting at intraplate seamounts is limited. Almost nothing is known about past hydrothermal activity at seamounts, because indicators are soon blanketed by sediment. This study provides evidence for temporary hydrothermal circulation at Henry Seamount, a re-activated Cretaceous volcano near El Hierro island, close to the current locus of the Canary Island hotspot. In the summit area at around 3000-3200 m water depth, we found areas with dense coverage by shell fragments from vesicomyid clams, a few living chemosymbiotic bivalves, and evidence for sites of weak fluid venting. Our observations suggest pulses of hydrothermal activity since some thousands or tens of thousands years, which is now waning. We also recovered glassy heterolithologic tephra and dispersed basaltic rock fragments from the summit area. Their freshness suggests eruption during the Pleistocene to Holocene, implying minor rejuvenated volcanism at Henry Seamount probably related to the nearby Canary hotspot. Heat flow values determined on the surrounding seafloor (49 ± 7 mW/m2) are close to the expected background for conductively cooled 155 Ma old crust; the proximity to the hotspot did not result in elevated basal heat flow. A weak increase in heat flow towards the southwestern seamount flank likely reflects recent local fluid circulation. We propose that hydrothermal circulation at Henry Seamount was, and still is, driven by heat pulses from weak rejuvenated volcanic activity. Our results suggest that even single eruptions at submarine intraplate volcanoes may give rise to ephemeral hydrothermal systems and generate potentially habitable environments.
    Keywords: Atlantic; Canary Islands; Center for Marine Environmental Sciences; heatflow; hydrothermal activity; MARUM; Seamount; vesicomyid clams
    Type: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
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