Methane clathrate

methane hydratemethane hydratesmethane icemethane clathratesclathrateclathratesNatural gas hydratenatural gas hydratesgas hydratesfrozen hydrates
Methane clathrate (CH 4 ·5.75H 2 O) or (4CH 4 ·23H 2 O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.wikipedia
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Methane

methane gasCH 4 liquid methane
Methane clathrate (CH 4 ·5.75H 2 O) or (4CH 4 ·23H 2 O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.
The largest reservoir of methane is under the seafloor in the form of methane clathrates.

Clathrate hydrate

gas hydratesgas hydrateclathrate hydrates
Methane clathrate (CH 4 ·5.75H 2 O) or (4CH 4 ·23H 2 O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.
Around 6.4 trillion (6.4×10 12 ) tonnes of methane is trapped in deposits of methane clathrate on the deep ocean floor.

Atmospheric methane

methanemethane cyclemethane in the atmosphere
In 2008, research on Antarctic Vostok and EPICA Dome C ice cores revealed that methane clathrates were also present in deep Antarctic ice cores and record a history of atmospheric methane concentrations, dating to 800,000 years ago.
At high pressures, such as are found on the bottom of the ocean, methane forms a solid clathrate with water, known as methane hydrate.

Gas hydrate stability zone

hydrate stability zonegas clathrate stability zonestability zone
These deposits are located within a mid-depth zone around 300–500 m thick in the sediments (the gas hydrate stability zone, or GHSZ) where they coexist with methane dissolved in the fresh, not salt, pore-waters.
Gas hydrate stability zone, abbreviated GHSZ, also referred to as methane hydrate stability zone (MHSZ) or hydrate stability zone (HSZ), refers to a zone and depth of the marine environment at which methane clathrates naturally exist in the Earth's crust.

Clathrate compound

clathrateclathratesclathrate compounds
Methane clathrate (CH 4 ·5.75H 2 O) or (4CH 4 ·23H 2 O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.
The most famous clathrates are methane clathrates where the hydrogen-bonded framework is contributed by water and the guest molecules are methane.

Siberia

SiberianEastern SiberiaEast Siberia
Continental deposits have been located in Siberia and Alaska in sandstone and siltstone beds at less than 800 m depth.
In 2008, a research expedition for the American Geophysical Union detected levels of methane up to 100 times above normal in the atmosphere above the Siberian Arctic, likely the result of methane clathrates being released through holes in a frozen 'lid' of seabed permafrost, around the outfall of the Lena River and the area between the Laptev Sea and East Siberian Sea.

Carbon

Ccarbonaceouscarbon atom
In comparison, the total carbon in the atmosphere is around 800 gigatons (see Carbon: Occurrence).
The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil, and methane clathrates.

Natural gas

gasgas-firednatural-gas
The sedimentary methane hydrate reservoir probably contains 2–10 times the currently known reserves of conventional natural gas,.
Natural gas is found in deep underground rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates.

Δ13C

δ 13 Cδ'' 13 CPDB
Here, the methane is isotopically light (δ 13 C < −60‰), which indicates that it is derived from the microbial reduction of CO 2.
The release of large amounts of methane clathrate can impact on global δ 13 C values, as at the Paleocene–Eocene Thermal Maximum.

Methanogen

methanogensmethane-producing microbesmethanogenic bacteria
The methane in gas hydrates is dominantly generated by microbial consortia degrading organic matter in low oxygen environments, with the methane itself produced by methanogenic archaea.
Under the correct conditions of pressure and temperature, biogenic methane can accumulate in massive deposits of methane clathrates, which account for a significant fraction of organic carbon in continental margin sediments and represent a key reservoir of a potent greenhouse gas.

Nankai Trough

Nankai megathrustNankaiNankai accretionary complex
The hydrate field from which the gas was extracted is located 50 km from central Japan in the Nankai Trough, 300 m under the sea.
The underlying fault, the Nankai megathrust, is the source of the devastating Nankai megathrust earthquakes, while the trough itself is potentially a major source of hydrocarbon fuel, in the form of methane clathrate.

Japan Oil, Gas and Metals National Corporation

JOGMEC
The University of Bergen's method is being field tested by ConocoPhillips and state-owned Japan Oil, Gas and Metals National Corporation (JOGMEC), and partially funded by the U.S. Department of Energy.
In March 2013, JOGMEC becomes the first to successfully extract methane hydrate from seabed deposits.

Deepwater Horizon oil spill

Deepwater Horizon'' oil spillBP oil spillGulf oil spill
At sufficient depths, methane complexes directly with water to form methane hydrates, as was observed during the Deepwater Horizon oil spill in 2010.
While this technique had worked in shallower water, it failed here when gas combined with cold water to form methane hydrate crystals that blocked the opening at the top of the dome.

Hydrocarbon

hydrocarbonsliquid hydrocarbonHC
In the less common second type found near the sediment surface some samples have a higher proportion of longer-chain hydrocarbons (< 99% methane) contained in a structure II clathrate. This represents a potentially important future source of hydrocarbon fuel.
Hydrocarbons are mined from oil sands and oil shale, and potentially extracted from sedimentary methane hydrates.

Blake Plateau

Blake Ridge
At Blake Ridge on the Atlantic continental rise, the GHSZ started at 190 m depth and continued to 450 m, where it reached equilibrium with the gaseous phase.
Methane and other gas hydrates are also found on the plateau.

Fuel

fuelsenergy-richFuel type
This represents a potentially important future source of hydrocarbon fuel.
Methane can be found in hydrocarbon fields, alone, associated with oil, or in the form of methane clathrates.

Mackenzie River

MackenzieMackenzie DeltaMackenzie Valley
In 2008, Canadian and Japanese researchers extracted a constant stream of natural gas from a test project at the Mallik gas hydrate site in the Mackenzie River delta.
In 2008, Canadian and Japanese researchers extracted a constant stream of natural gas from a test project at the Mallik methane hydrate field in the Mackenzie Delta.

The Swarm (Schätzing novel)

The SwarmThe Swarm'' (Schätzing novel)Der Schwarm
After several expeditions it becomes clear that the worms, together with bacteria, are destabilizing the methane clathrate in the continental shelf.

Ethylene glycol

glycolmonoethylene glycolethanediol
This is commonly achieved by removing water, or by the addition of ethylene glycol (MEG) or methanol (i.e. common antifreeze), which act to depress the temperature at which hydrates will form.
Ethylene glycol is widely used to inhibit the formation of natural gas clathrates (hydrates) in long multiphase pipelines that convey natural gas from remote gas fields to a gas processing facility.

Last Glacial Period

last ice ageDevensianIce Age
Scientists from the Center for Arctic Gas Hydrate (CAGE), Environment and Climate at the Arctic University of Norway, published a study in June 2017, describing over a hundred ocean sediment craters, some 300 meters wide and up to 30 meters deep, formed due to explosive eruptions, attributed to destabilizing methane hydrates, following ice-sheet retreat during the last glacial period, around 15,000 years ago, a few centuries after the Bølling-Allerød warming.
describing over a hundred ocean sediment craters, some 3,000 meters wide and up to 300 meters deep, formed by explosive eruptions of methane from destabilized methane hydrates, following ice-sheet retreat during the last glacial period, around 12,000 years ago.

South China Sea

East SeaSouth ChinaWest Philippine Sea
Both Japan and China announced in May 2017 a breakthrough for mining methane clathrates, when they extracted methane from hydrates in the South China Sea.
China announced in May 2017 a breakthrough for mining methane clathrates, when they extracted methane from hydrates in the South China Sea.

Permian–Triassic extinction event

Permian-Triassic extinction eventPermian extinctionPermian-Triassic boundary
Events possibly linked in this way are the Permian-Triassic extinction event and the Paleocene-Eocene Thermal Maximum.
Prior to consideration of the inclusion of roasting carbonate sediments by volcanism, the only proposed mechanism sufficient to cause a global 1% reduction in the 13 C/ 12 C ratio was the release of methane from methane clathrates.

Permafrost

discontinuous permafrostcontinuous permafrostsporadic permafrost
Climate scientists like James E. Hansen predict that methane clathrates in permafrost regions will be released because of global warming, unleashing powerful feedback forces that may cause runaway climate change.
Large quantities of methane are stored in the Arctic in natural gas deposits, in permafrost, and as submarine clathrates.

Long-term effects of global warming

long-term impacts
Methane clathrate, also called methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure.

Paleocene–Eocene Thermal Maximum

Paleocene-Eocene Thermal MaximumPETMPaleocene-Eocene transition
Events possibly linked in this way are the Permian-Triassic extinction event and the Paleocene-Eocene Thermal Maximum.
The most obvious feedback mechanism that could amplify the initial perturbation is that of methane clathrates.