Global and local variations of interstitial sulfate gradients in deep-water, continental margin sediments: Sensitivity to underlying methane and gas hydrates

Borowski, Walter S; Paull, C. K.; Ussler, William

doi:10.1016/s0025-3227(99)00004-3

Cited by 347 publications

(248 citation statements)

References 66 publications

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“…This reaction prevents sulfate and methane from coexisting at high concentrations in sediment porewaters. Typically both species diffuse toward their mutual annihilation at a well-defined methane/sulfate boundary (Borowski et al, 1996(Borowski et al, , 1999D'Hondt et al, 2004). After the depletion of sulfate, methane can be produced from solid organic carbon, or by reaction of dissolved organic carbon, notably acetate, carried into the methanogenesis zone by diffusion or pore water advection.…”

Section: Methane Productionmentioning

confidence: 99%

Methane hydrate stability and anthropogenic climate change

2007

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Abstract. Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO 2 .Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

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Section: Methane Productionmentioning

confidence: 99%

Methane hydrate stability and anthropogenic climate change

2007

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“…Furthermore, fast sulfate reduction rates induce shallower depth of the SMI. Therefore, the profiles of interstitial sulfate concentration and the methane concentration of pore space in sediments can provide an indicator for further estimation of methane fluxes from buried sediments if there are gas hydrates beneath the sea floor (Borowski et al 1996(Borowski et al , 1999. Geochemical profiles for cored samples are plotted in Fig.…”

Section: Very Shallow Depth Of Sulfate Methane Interfacementioning

confidence: 99%

Extremely High Methane Concentration in Bottom Water and Cored Sediments from Offshore Southwestern Taiwan

Chuang¹,

Yang²,

Lin³

et al. 2006

Terr. Atmos. Ocean. Sci.

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ABSTRACT1 Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC 2 Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC 3 Central Geological Survey, MOEA, Taipei, Taiwan, ROC * Corresponding author address: Prof. Tsanyao Frank Yang, Department of Geosciences, National Taiwan University, Taipei, Taiwan, ROC; E-mail: tyyang@ntu.edu.tw It has been found that Bottom Simulating Reflections (BSRs), which infer the existence of potential gas hydrates underneath seafloor sediments, are widely distributed in offshore southwestern Taiwan. Fluids and gases derived from dissociation of gas hydrates, which are typically methane enriched, affect the composition of seawater and sediments near venting areas. Hence, methane concentration of seawater and sediments become useful proxies for exploration of potential gas hydrates in a given area. We systematically collected bottom waters and sedimentary core samples for dissolved and pore-space gas analyses through five cruises: ORI-697, ORI-718, ORII-1207, ORII-1230, and ORI-732 from 2003 to 2005 in this study. Some sites with extremely high methane concentrations have been found in offshore southwestern Taiwan, e.g., sites G23 of ORI-697, N8 of ORI-718, and G96 of ORI-732. The methane concentrations of cored sediments display an increasing trend with depth. Furthermore, the down-core profiles of methane and sulfate reveal very shallow depths of sulfate methane interface (SMI) at some sites in this study. It implies sulfate reduction being mainly driven by the process of anaerobic methane oxidation (AMO) in sediments; thus indicating that there is a methane-enriched venting source, which may be the product of dissociation of gas hydrates in this area.

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“…The depth of the SMTZ is dependent on (1) sulfate depletion resulting from organic matter degradation (Borowski et al, 1999); (2) sulfate supply by diffusion, bioirrigation and sulfide re-oxidation reactions (Dale et al, 2009); (3) the flux of methane from below the SMTZ (Borowski et al, 1996); and (4) the advective fluid flow rate (Treude et al, 2003;Orcutt et al, 2011). At continental margins, the SMTZ can sometimes be located several hundreds of meters below the seafloor (mbsf) (Borowski et al, 1999). In coastal sediments, sulfate is consumed rapidly via organoclastic sulfate reduction fueled by an enhanced supply of organic matter, and, subsequently, the SMTZ is often located closer to the sediment-water interface compared to sediments in greater water depths (Hinrichs and Boetius, 2002).…”

Section: Introductionmentioning

confidence: 99%

Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore of Costa Rica

et al. 2015

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Abstract. Large amounts of methane are delivered by fluids through the erosive forearc of the convergent margin offshore of Costa Rica and lead to the formation of cold seeps at the sediment surface. Besides mud extrusion, numerous cold seeps are created by landslides induced by seamount subduction or fluid migration along major faults. Most of the dissolved methane migrating through the sediments of cold seeps is oxidized within the benthic microbial methane filter by anaerobic oxidation of methane (AOM). Measurements of AOM and sulfate reduction as well as numerical modeling of porewater profiles revealed a highly active and efficient benthic methane filter at the Quepos Slide site, a landslide on the continental slope between the Nicoya and Osa Peninsula. Integrated areal rates of AOM ranged from 12.9 ± 6.0 to 45.2 ± 11.5 mmol m −2 d −1 , with only 1 to 2.5 % of the upward methane flux being released into the water column.Additionally, two parallel sediment cores from Quepos Slide were used for in vitro experiments in a recently developed sediment-flow-through (SLOT) system to simulate an increased fluid and methane flux from the bottom of the sediment core. The benthic methane filter revealed a high adaptability whereby the methane oxidation efficiency responded to the increased fluid flow within ca. 170 d. To our knowledge, this study provides the first estimation of the natural biogeochemical response of seep sediments to changes in fluid flow.

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Global and local variations of interstitial sulfate gradients in deep-water, continental margin sediments: Sensitivity to underlying methane and gas hydrates

Cited by 347 publications

References 66 publications

Methane hydrate stability and anthropogenic climate change

Methane hydrate stability and anthropogenic climate change

Extremely High Methane Concentration in Bottom Water and Cored Sediments from Offshore Southwestern Taiwan

Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore of Costa Rica

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