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500 new methane vents found

  1. Oct 22, 2016 #1

    wolram

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    I do not know if this is a worry but it seems like our oceans are leaking green house gases.

    https://www.sciencedaily.com/releases/2016/10/161020103858.htm

    Date:
    October 20, 2016
    Source:
    National Ocean Exploration Forum
    Summary:
    Five hundred vents newly discovered off the US West Coast, each bubbling methane from Earth's belly, top a long list of revelations about "submerged America" being celebrated by leading marine explorers. The discoveries double to about 1,000 the number of such vents now known to exist along the continental margins of the USA. This fizzing methane is a powerful greenhouse gas if it escapes into the atmosphere; a clean burning fuel if safely captured.
     
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  3. Oct 22, 2016 #2

    Bystander

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    You are aware that the marine environment is terra incognito?
     
  4. Oct 22, 2016 #3
    Supposedly, methanogens eat the methane before it escapes into the atmosphere. A few years ago I asked what if a massive zone of offshore sediment unleashed its methane due to some sort of agitation, like a submarine slide. That "what if" isn't answered to my satisfaction. The American Geophysical Union's Global Environmental Focus Group started out as Global Warming FG, then morphed to Climate Change FG, and finally to its present incarnation as Global Environmental Change FG. We realized that thee were processes that can't be processed into climate change models, but that would seemingly have an influence at some point. Mapping sediment and organic matter deposition into oceans and lakes and them measuring or estimating conversion to methane was something that needed to be addressed. I started seismically mapping methane clathrates in 1974 in the Arctic and then offshore California. Methane is ubiquitous and the main line of defense is the methanogenic bacterium. I suppose we could lay tarps on the seafloor and create methane balloons to exploit escaping methane. I believe it was Arco that tried a funnel system to collect gas from seeps in the Santa Barbara Channel, not that it was expected to be profitable.
    http://www.sbcountyplanning.org/energy/information/seepspaper.asp
     
  5. Oct 22, 2016 #4

    Fervent Freyja

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  6. Oct 23, 2016 #5
    Isotopically heavy oxygen-containing siderite derive from the decomposition of methane hydrate
    https://www.researchgate.net/publication/249519392_Isotopically_heavy_oxygen-containing_siderite_derive_from_the_decomposition_of_methane_hydrate [Broken]


    The earliest Deep Sea Drilling Project didn't always manage to collect methane in the samples, usually because it apparently escaped by bubbling out of the core. What they did find very often was siderite, FeCO3, which later became a proxy for methane in those cores. . This relationship of siderite to methane may prove useful in assessing the extent and possible origin of methane on Mars.
    Generation of methane in the Earth’s mantle: In situ high pressure–temperature measurements of carbonate reduction
    http://www.pnas.org/content/101/39/14023.full.pdf
    This paper also sheds some insights into Freya's post.
    The methane seeps in the Santa Barbara Channel tend to be over oil- and gas-bearing structures at depth and are biogenic. Abiogenic methane may account for most of the methane from hydrothermal vents. Methane in other methane hydrates is derived from organic material.
     
    Last edited by a moderator: May 8, 2017
  7. Oct 23, 2016 #6
  8. Nov 6, 2016 #7

    BillTre

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    It is my understanding that the methane clathrates are thought to be potentially released as temperatures rise. Such as in the Arctic.
    Could that have an effect that far south?

    You mentioned physical disturbances (undersea landslides). Would these have their effect through a rapid change in the pressures the methane clathrates reside at?
     
  9. Nov 6, 2016 #8
    One of the areas of interest is the Blake Ridge off the coast of South Carolina. It's been considered off and on in terms of methane production and consequently has been studied in great detail.
    Seismic Studies on the Blake Ridge Gas Hydrates
    http://woodshole.er.usgs.gov/operations/obs/blakeridge95.html
    "The base of the gas hydrate zone may represent a zone of weakness within the sediment column because hydrates, which act as bonding agents within the hydrate bearing layer, may inhibit normal sediment consolidation and cementation. Also, free gas may be accumulated at the base of the hydrate stability zone leading to excess pore pressure. Along the southeastern U.S. coast, locations of slope failure apparently concentrate slightly seaward of the line at which the hydrate stability zone intercepts the seafloor, although the gentle dip of the seafloor of <6 at these depths would indicate a relatively stable slope (Booth et al., 1994), an observation which clearly supports the hypothesis of hydrates being potentially involved in marine slope failure."

    Faulted structure of the bottom simulating reflector on the Blake Ridge, western North Atlantic
    http://geology.gsapubs.org/content/21/9/833.full.pdf+html

    Abstract
    High-resolution multichannel seismic data collected from the Blake Ridge in the western North Atlantic by the Naval Research Laboratory's Deep Towed Acoustics/Geophysics System (DTAGS) show that the bottom simulating reflector (BSR) in this area is the reflection from the interface between an ∼440-m- thick section of hydrate-bearing sediment overlying an ∼5-m-thick layer of methane gas-rich sediment. The high resolution attainable by the deep-tow seismic system reveals normal-fault offsets of ∼20 m in the BSR. These growth faults may provide a path for vertical migration of methane initially concentrated beneath the hydrate-bearing sediment, enabling hydrate to form throughout sediment above the BSR. Because the BSR represents a methane gas- methane hydrate phase boundary rather than a lithologic or diagenetic horizon, the observed offset of the BSR itself reflects discontinuities in the pressure- temperature field across the fault zones where they intersect the BSR.

    This was more along the lines of the work I did. The abstract highlights and touches on some of the potential temperature and pressure issues that could be encountered on the seafloor. One of the problems I had when I started out was that the reflection off the seafloor can be repeated a ways down the seismic section and can be filtered out Because the hydrate zone often follows the same pattern as the seafloor, it can be disregarded as just a BSR. This paper shows how the hydrate zone an be offset by faulting. It also shows how thick and complex the total methane zone can be.
    My concern was that this zone could be disrupted by something like a slide. I presented this, in what might be a naive and simplistic synthesis, something as catastrophic as a submarine slide or an earthquake breaking up the clathrate cages in the hydrate zone and also ripping up the methane zone below the hydrates, creating a massive accumulation of methane in the water. I presented this to a group at Woods Hole/MIT and got a variation of this:

    Extensive release of methane from Arctic seabed west of Svalbard during summer 2014 does not influence the atmosphere
    http://onlinelibrary.wiley.com/doi/10.1002/2016GL068999/full
    "Model approaches taking potential CH
    4 emissions from both dissolved and bubble-released CH4 from a larger region into account reveal a maximum flux compatible with the observed atmospheric CH4 mixing ratios of 2.4–3.8 nmol m−2 s−1. This is too low to have an impact on the atmospheric summer CH4 budget in the year 2014.
    I'll try to find a paper that gets into the thermo- and pycnocline constraints on the upward movement of the methane that keeps it in the food pen for methane eaters. I'm thinking that the dynamics of an accumulation of methane in seawater that has been agitated by a seafloor disturbance like a slide or an earthquake is quite a bit different than the more passive bubbling up from a seep.












    In what might be a naive and simplistic synthesis, I see something as catastrophic as a submarine slide or an earthquake breaking up the clathrate cages in the hydrate zone and also ripping up the methane zone below the hydrates, creating a massive accumulation of methane in the water.
     
  10. Nov 6, 2016 #9
    Related to this is the idea of abrupt climate change.
    Abrupt Climate Change Focus Of U.S. National Laboratories
    https://www.sciencedaily.com/releases/2008/09/080918192943.htm?trendmd-shared=0

    This is a little too fluffed up for me, but it introduces IMPACTS, which ran from 2008 until 2013.

    IMPACTS Project Tasks
    http://esd1.lbl.gov/research/projects/abrupt_climate_change/impacts/tasks.html#clathrates

    Abrupt Climate Change from Methane Hydrate Destabilization
    There is lingering concern that vast methane stocks locked in a stable ice-like state at the bottom of the ocean (known variously as methane clathrate and methane hydrate) could be released in the future due to a warming ocean and/or ocean circulation changes. The current abundance of carbon stored in hydrates is generally believed to be greater than the recoverable stocks of all the other fossil fuels combined (Buffet and Archer, 2004; Gornitz & Fung, 1994), and methane is 72 times more potent as a greenhouse gas than is carbon dioxide over 20-year time horizons (IPCC, 2007a). There is evidence that methane hydrate releases have caused abrupt climate changes in the past, such as the Paleocene-Eocene Thermal Maximum 55 million years ago when the planet abruptly warmed 5-8K (Dickens, 2003). There is also disputed evidence that hydrate dissociation greatly amplified and accelerated global warming episodes in the late Quaternary period (Kennett et al., 2000). Whether or not a consensus exists regarding paleoclimate data, the stability of the contemporary hydrate inventory to the unprecedented temperature rise from anthropogenic emissions requires a careful assessment. Fortunately, our estimates for ocean-floor warming indicate that, for most of the ocean, hydrates are stable under the influence of moderate temperature changes (Reagan and Moridis, 2007; Archer, 2007) and massive methane releases remain a long way off (centuries to millennia). However, there are some regions with large hydrate abundances that are far less stable to climate change, notably the Arctic, which contains hundreds of Gton of methane with a time scale for release of decades (review by Archer, 2007; Reagan and Moridis, 2007), and the release is predicted to be abrupt at each location because the hydrates lie close to the edge of the gas hydrate stability zone defined by temperature and pressure (see figure 4.1). Plausible scenarios could lead to methane becoming more important than CO2 as a greenhouse gas on a time-scale of decades, with the associated warming leading to further hydrate dissociation, as well as terrestrial permafrost melting, that will release additional methane and be self-sustaining. In this project we will assess the strength and consequences of methane hydrate dissociation this century, including the likelihood we will cross a tipping point, and address the risks of shifting storm tracks, increased surface ozone, reduced stratospheric ozone, increasing the strength and frequency of the Arctic ozone hole, and the formation of oceanic dead-zones (hypoxia). (Wuebbles & Hayhoe, 2002)

     
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