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  • 1
    Online Resource
    Online Resource
    "PALEOVAN", International Continental Scientific Drilling Program (ICDP) : site survey results and perspectives (2009)
    Associated volumes
    Details Availability
    In: Quaternary science reviews, Amsterdam [u.a.] : Elsevier, 1982, 28(2009), 15/16, Seite 1555-1567, 0277-3791
    In: volume:28
    In: year:2009
    In: number:15/16
    In: pages:1555-1567
    Description / Table of Contents: Lake Van is the fourth largest terminal lake in the world (volume 607 km3, area 3570 km2, maximum depth 460 m), extending for 130 km WSWENE on the Eastern Anatolian High Plateau, Turkey. The sedimentary record of Lake Van, partly laminated, has the potential to obtain a long and continuous continental sequence that covers several glacialinterglacial cycles (ca 500 kyr). Therefore, Lake Van is a key site within the International Continental Scientific Drilling Program (ICDP) for the investigation of the Quaternary climate evolution in the Near East (‘PALEOVAN’). As preparation for an ICDP drilling campaign, a site survey was carried out during the past years. We collected 50 seismic profiles with a total length of ~850 km to identify continuous undisturbed sedimentary sequences for potential ICDP locations. Based on the seismic results, we cored 10 different locations to water depths of up to 420 m. Multidisciplinary scientific work at positions of a proposed ICDP drill site included measurements of magnetic susceptibility, physical properties, stable isotopes, XRF scans, and pollen and spores. This core extends back to the Last Glacial Maximum (LGM), a more extended record than all the other Lake Van cores obtained to date. Both coring and seismic data do not show any indication that the deepest part of the lake (Tatvan Basin, Ahlat Ridge) was dry or almost dry during past times. These results show potential for obtaining a continuous undisturbed, long continental palaeoclimate record. In addition, this paper discusses the potential of "PALEOVAN" to establish new results on the dynamics of lake level fluctuations, noble gas concentration in pore water of the lake sediment, history of volcanism and volcanic activities based on tephrostratigraphy, and paleoseismic and earthquake activities.
    Type of Medium: Online Resource
    Pages: Ill., graph. Darst
    ISSN: 0277-3791
    DOI: 10.1016/j.quascirev.2009.03.002
    Language: English
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  • 2
    Online Resource
    Online Resource
    Methane seepage along the Hikurangi Margin of New Zealand : geochemical and physical data from the water column, sea surface and atmosphere (2010)
    Associated volumes
    Details Availability
    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, 272(2010), Seite 170-188, 1872-6151
    In: volume:272
    In: year:2010
    In: pages:170-188
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 1872-6151
    DOI: 10.1016/j.margeo.2010.01.001
    Language: English
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  • 3
    Electronic Resource
    Electronic Resource
    Noble Gas and Major Element Constraints on the Water Dynamics in an Alpine Floodplain (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 39 (2001), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The hydrogeological system of an ecologically sensitive alpine floodplain in the Valle di Blenio, Switzerland, was investigated using hydrochemical and 3H-3He dating methods. Water samples from six wells and from different surface locations were analyzed. The analysis of the concentrations of major ions in conjunction with age determination by the 3H-3He-method allowed the main hydrological properties of the system to be consistently characterized. Two geochemically distinct water zones can be distinguished: Ca-SO4-dominated water from the main river and Ca-HCO3-dominated floodplain water. The floodplain water component characterizes the whole floodplain including the surficial hillslope drainage system. Within the ground water samples, two spatially and temporally different types of water can be determined. A younger (age 〈 1.5 years), less mineralized water is found in the upper part of the aquifer during the summer season. The underlying aquifer zone contains older and more highly mineralized water. However, the general hydrochemical characterization of both types of ground water is similar. In winter, the water ages increase with decreasing ground water levels. Because precipitation is stored temporarily in the snow cover, the contribution of the younger near-surface ground water decreases, resulting in higher apparent water ages and higher mineralization in the upper zone of the aquifer. Water exchange between the main river and the ground water system is limited to ground water exfiltration from the shallow aquifer zone, whereas the hydrochemical separation of the deeper aquifer zone indicates the isolation of the deeper ground water from the main river.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2001.tb02472.x
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    Paper (German National Licenses)
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  • 4
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    Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean: A review (2016)
    In:  EPIC3Limnology & Oceanography
    Details
    Publication Date: 2016-06-07
    Description: Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the seabed, the fate of this methane in the water column, and potential for its release to the atmosphere. We find that, at present, fluxes of dissolved methane are significantly moderated by anaerobic and aerobic oxidation of methane. If methane fluxes increase then a greater proportion of methane will be transported by advection or in the gas phase, which reduces the efficiency of the methanotrophic sink. Higher freshwater discharge to Arctic shelf seas may increase stratification and inhibit transfer of methane gas to surface waters, although there is some evidence that increased stratification may lead to warming of sub-pycnocline waters, increasing the potential for hydrate dissociation. Loss of sea-ice is likely to increase wind speeds and sea-air exchange of methane will consequently increase. Studies of the distribution and cycling of methane beneath and within sea ice are limited, but it seems likely that the sea-air methane flux is higher during melting in seasonally ice-covered regions. Our review reveals that increased observations around especially the anaerobic and aerobic oxidation of methane, bubble transport, and the effects of ice cover, are required to fully understand the linkages and feedback pathways between climate warming and release of methane from marine sediments.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
  • 5
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    Using helium and other noble gases in ocean sediments to characterize active methane seepage off the coast of New Zealand (2013)
    Elsevier
    In:  Marine Geology, 344 . pp. 34-40.
    Details
    Publication Date: 2014-04-22
    Description: Recently developed analytical techniques to determine the abundances of noble gases in sediment pore water allow noble-gas concentrations and isotope ratios to be measured easily and routinely in lacustrine sediments. We applied these techniques for the first time to ocean sediments to investigate an active cold methane seepage system located in the South Pacific off the coast of the North Island of New Zealand using 3He/4He ratios determined in the sediment pore water. The results show that more 3He-rich fluids are released in the vicinity of the Pacific–Australian subduction zone than at the forearc stations located closer to the New Zealand coast. However, the He isotope signature in the sediment column indicates that only a minor part of the He emanating from deeper strata originates from a depleted mantle source. Hence, most He in the pore water is produced locally by the radioactive decay of U and Th in the sediment minerals or in the underlying crustal rocks. Such an occurrence of isotopically heavy crustal He also suggests that the source of the largest fraction of methane is a near-surface geochemical reservoir. This finding is in line with a previous δ13C study in the water column which concluded that the emanating methane is most likely of biological origin and is formed in the upper few meters of the sediment column. Moreover, the prevalence of isotopically heavy He agrees well with the outcome of other previous studies on island arc systems which indicate that the forearc regions are characterized by crustal He emission, whereas the volcanic arc region is characterized by the presence of mantle He associated with rising magma.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.margeo.2013.07.010
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Impact of lake level change on deep-water renewal and oxic conditions in deep saline Lake Van, Turkey (2010)
    AGU (American Geophysical Union)
    In:  Water Resources Research, 46 (11). W11508.
    Details
    Publication Date: 2014-04-22
    Description: Changes in the hydrological regime of the saline closed basin Lake Van, a large, deep lake in eastern Turkey, resulted in a lake level increase by about 2 m between 1988 and 1995, followed by a 1.5 m decrease until 2003 and a relatively constant lake level thereafter. Based on measurements of transient tracers (sulfur hexafluoride, CFC-12, 3H, 3He, 4He, Ne), dissolved oxygen, light transmission, conductivity-temperature-depth profiles, and thermistor data, we investigate the implications associated with lake level fluctuations for deep-water renewal and oxygenation. Our data suggest that deep-water renewal was significantly reduced in Lake Van between 1990 and 2005. This change in mixing conditions resulted in the formation of a more than 100 m thick anoxic deep-water body below 325 m depth. Apparently, the freshwater inflows responsible for the lake level rise between 1988 and 1995 decreased the salinity of the surface water sufficiently that the generation of density plumes during winter cooling was substantially reduced compared to that in the years before the lake level rise. Significant renewal and oxygenation of the deep water did not occur until at least 2005, although by 2003 the lake level was back to almost the same level as in 1988. This study suggests that short-term changes in the hydrological regime, resulting in lake level changes of a couple of meters, can lead to significant and long-lasting changes in deep-water renewal and oxic conditions in deep saline lakes.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    DOI: 10.1029/2009WR008555
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Spatial distribution and flux of terrigenic He dissolved in the sediment pore water of Lake Van (Turkey) (2011)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 75 (10). pp. 2848-2864.
    Details
    Publication Date: 2014-04-22
    Description: In this study, the largest ever carried out to measure noble gases in the pore water of unconsolidated sediments in lakes, the emission of terrigenic He through the sediment column of Lake Van was successfully mapped on the local scale. The main input of He to the water body occurs at the borders of a deep basin within the lake, which is probably the remains of a collapsed caldera. The 3He/4He3He/4He ratio identifies the He injected into the sedimentary column of Lake Van as a mixture of He released from a mantle source and radiogenic He of crustal origin (3He/4He∼2.6-4.1×10-6)(3He/4He∼2.6-4.1×10-6). During passage through the pore space, terrigenic He seems to be further enriched in radiogenic He that is most likely produced in the sediment column. In fact, two distinct trends in isotopic composition can be distinguished in the He injected from the lake basement into the sediments. One of these characterizes samples from the shallow water, the other characterizes samples from the deep basin. However, both of these trends are related to the same source of terrigenic He. The He fluxes determined seem to be characteristic of each sampling location and might be considered as a proxy for the fluid permeability of the deep sediment column. These new findings provide insight into the process of fluid transport within the sediments and into the process of formation of the lake basin. Moreover, the isotopic signature of the He that emanates into the water column of Lake Van is strongly affected by the mixing conditions prevailing in the overlying water body. This fact misled previous studies to interpret the terrigenic He in Lake Van as being solely of mantle origin (3He/4He∼10-5)(3He/4He∼10-5).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2011.02.038
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean: A review (2016)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 61 (S1). pp. 301-309.
    Details
    Publication Date: 2019-09-24
    Description: Large quantities of methane are stored in hydrates and permafrost within shallow marine sediments in the Arctic Ocean. These reservoirs are highly sensitive to climate warming, but the fate of methane released from sediments is uncertain. Here, we review the principal physical and biogeochemical processes that regulate methane fluxes across the seabed, the fate of this methane in the water column, and potential for its release to the atmosphere. We find that, at present, fluxes of dissolved methane are significantly moderated by anaerobic and aerobic oxidation of methane. If methane fluxes increase then a greater proportion of methane will be transported by advection or in the gas phase, which reduces the efficiency of the methanotrophic sink. Higher freshwater discharge to Arctic shelf seas may increase stratification and inhibit transfer of methane gas to surface waters, although there is some evidence that increased stratification may lead to warming of sub-pycnocline waters, increasing the potential for hydrate dissociation. Loss of sea-ice is likely to increase wind speeds and seaair exchange of methane will consequently increase. Studies of the distribution and cycling of methane beneath and within sea ice are limited, but it seems likely that the sea-air methane flux is higher during melting in seasonally ice-covered regions. Our review reveals that increased observations around especially the anaerobic and aerobic oxidation of methane, bubble transport, and the effects of ice cover, are required to fully understand the linkages and feedback pathways between climate warming and release of methane from marine sediments.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1002/lno.10307
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    A portable and autonomous mass spectrometric system for on-site environmental gas analysis (2016)
    American Chemistry Society
    In:  Environmental Science & Technology, 50 (24). pp. 13455-13463.
    Details
    Publication Date: 2019-02-01
    Description: We developed a portable mass spectrometric system (“miniRuedi”) for quantificaton of the partial pressures of He, Ne (in dry gas), Ar, Kr, N2, O2, CO2, and CH4 in gaseous and aqueous matrices in environmental systems with an analytical uncertainty of 1−3%. The miniRuedi does not require any purification or other preparation of the sampled gases and therefore allows maintenance- free and autonomous operation. The apparatus is most suitable for on-site gas analysis during field work and at remote locations due to its small size (60 cm × 40 cm × 14 cm), low weight (13 kg), and low power consumption (50 W). The gases are continuously sampled and transferred through a capillary pressure reduction system into a vacuum chamber, where they are analyzed using a quadrupole mass spectrometer with a time resolution of ≲1 min. The low gas consumption rate (〈0.1 mL/min) minimizes interference with the natural mass balance of gases in environmental systems, and allows the unbiased quantification of dissolved-gas concentrations in water by gas/water equilibration using membrane contractors (gasequilibrium membrane-inlet mass spectrometry, GE-MIMS). The performance of the miniRuedi is demonstrated in laboratory and field tests, and its utility is illustrated in field applications related to soil-gas formation, lake/atmosphere gas exchange, and seafloor gas emanations.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1021/acs.est.6b03669
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    RV SONNE 241 Cruise Report / Fahrtbericht, Manzanillo, 23.6.2015 – Guayaquil, 24.7.2015 : SO241 - MAKS: Magmatism induced carbon escape from marine sediments as a climate driver – Guaymas Basin, Gulf of California (2015)
    GEOMAR Helmholtz Centre for Ocean Research Kiel
    In:  GEOMAR Helmholtz Centre for Ocean Research Kiel, 74 pp.
    Details
    Publication Date: 2018-04-27
    Description: SO241 set out to test the hypothesis that rift-related magmatism is able to increase carbon emissions from sedimentary basins to the extent that they can actively force climate. To this end we investigated a study area in the Guaymas Basin in the Gulf of California which is one of very few geological settings where rift-related magmatism presently leads to magmatic intrusions into a sediment basin. During the cruise we collected 1100 km of 2D seismic lines to image the extent and volume of magmatic intrusions as well as the extent of metamorphic overprinting of the surrounding sediments and associated subsurface sediment mobilization. We selected three typical seep sites above magmatic intrusions for detailed geochemical studies using gravity corers, multicorers and TV grab. With these samples we will be able to determine the pore water composition to assess the amount and composition of hydrocarbon compounds that are released from these systems. Detailed ocean bottom seismometer measurements at a seep site in the center of the Guaymas Basin will provide further insights into effects of magmatic intrusions on carbon release and diagenetic overprinting of the sediments. It will be possible to reconstruct its long-term seepage history from big carbonate blocks that we have collected with a TV-grab. The northeastern margin of the Guaymas Basin is known for the presence of gas hydrates. During the cruise we collected several seismic lines, which show a clear but unusually shallow BSR indicating high heat flow in the region. Using the seismic data we discovered a previously unknown geological structure on the flank of the northern rift segment: a large mound that seems to consist entirely of black smoker deposits. It seems to be the result of a recent intrusion into the underlying sediments and changes the view how such systems function. The structure was investigated with a comprehensive geochemical, geothermal, and video surveying program which revealed at least seven vents that are active simultaneously. These vents inject methane and helium-rich vent fluids several hundred meters up into the water column. These findings suggest that large-scale magmatism, for example during the opening of an ocean basin under the influence of a hot spot, can be an effective way of liberating large amounts of carbon high up into the water column. The data collected during SO241 will allow us to constrain the amount of carbon that can escape into the atmosphere during LIP emplacement and their relevance on a global scale can be assessed. In addition to reaching the main objectives of the project we discovered a large landslide complex that was probably associated with a tsunami.
    Type: Report , NonPeerReviewed
    Format: text
    DOI: 10.3289/CR_S241
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    OceanRep: Report - Cruise Report
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