A methane chimney or gas chimney is a rising column of natural gas, mainly methane, within a water or sediment column. The contrast in physical properties between the gas phase and the surrounding water makes such chimneys visible in oceanographic and geophysical data. In some cases, gas bubbles released at the seafloor may dissolve before they reach the ocean surface, but the increased hydrocarbon concentration may still be measured by chemical oceanographic techniques.
In some locations along Russia’s northern coast, methane rising from the sea floor to the surface has caused the sea to foam. [1] However, most methane chimneys do not produce such visible signs at the sea surface. Instead, plumes are identified by a combination of chemical and physical oceanographic and geologic data. [2] Plumes of methane bubbles, whether in the water column or subseafloor sediments, have lower density and sound speed than the surrounding water. As such, these plumes can be imaged by a variety of acoustic techniques, including seismic reflection data and conventional fishfinders. Dissolved methane is usually identified through widespread chemical analysis of water samples, including chromatography of gasses extracted from the headspace of seawater samples taken at depth (headspace is the space above a sample in a sealed container, which forms as higher temperature and lower pressure allows gasses to come out of solution). Continuous measurements of methane concentration in seawater can be made by underway ships using cavity ring-down spectroscopy.
Large deposits of frozen methane, when thawing, release gas into the environment. [3] In cases of sub-sea permafrost, the methane gas may be dissolved in the seawater before reaching the surface; however, in a number of sites around the world, these methane chimneys release the gas directly into the atmosphere, contributing to global warming. [4] Research teams in the Arctic measured concentrations of methane to be the highest ever recorded in the summertime. [5] The thawing underwater permafrost is affecting methane release in two ways: thawing organic matter trapped in the permafrost releases methane and carbon dioxide as it decomposes, and methane in gas or solid form beneath the thawing permafrost seeps up through the now-soft soil and escapes into the atmosphere. [6] In part of the International Siberian Shelf Study, which looked at arctic methane emissions, scientists discovered that methane concentrations released from subsea chimneys and seeps were often 100 times higher than background levels, and methane gas has 20 times the heat-trapping capabilities as carbon dioxide. [7]
Methane chimneys play a major role in marine life, creating chemical deposits that are habitat to a plethora of life. [8] These highly-productive ecosystems occur in a wide range of marine geological settings across the world. [9] Chimneys teem with organisms that feed on the methane and sulfide that are released from the chimneys. [10] Life surrounding the marine methane chimneys consumes 90% of methane released, preventing it from entering the atmosphere. [11] Microbes around methane chimneys form the basis for the entire food web; these microbes are chemolithotrophs, and thus do not require sunlight or oxygen to survive. [12] Marine methane chimneys produce minerals that fertilize the ocean, creating optimal spawning habitats for deep-sea sharks and other fish. [13] [14] They are also host to deep-sea crabs, shrimp, mussels, clams, and more shellfish. The expanse of life and ecosystems that these vents provide is still largely unexplored. [15]
In hydrocarbon exploration, gas chimneys revealed on seismic reflection data are indicators of active gas migration [16] and a working petroleum system.
Trees in swampy, low-lying areas can conduct methane produced in soils up through their stems and out their leaves. Other plants in bogs and marshes also act in this way. In the Amazon Rainforest, recent studies have named trees a "massive chimney for pumping out methane". [17] Findings estimated that the Amazon Rainforest emits around 40 million tons of methane per year, as much as the entire arctic permafrost systems. [18] When large portions of the Amazon Basin flood, they create ideal conditions for high-level methane production. [19] The methane flux is a result of abiotic factors such as soil moisture and climate. As seen in the figure 2 of the Quercus cerris tree in Hungary, a cool climate plant that demands moderate soil moisture can be observed to contain flammable concentrations of methane emitted from the stem contraption. [20] [21]
Trees are not the only plants that act as methane chimneys; however, studies have shown that species with greater root volume and biomass tend to exhibit a stronger chimney effect, and methane emissions in plant species are increased by raising the water table. [22]
Methane clathrate (CH4·5.75H2O) or (4CH4·23H2O), 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. Originally thought to occur only in the outer regions of the Solar System, where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of the Earth (approx. 1100m below the sea level). Methane hydrate is formed when hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in oceans.
Clathrate hydrates, or gas hydrates, clathrates, or hydrates, are crystalline water-based solids physically resembling ice, in which small non-polar molecules or polar molecules with large hydrophobic moieties are trapped inside "cages" of hydrogen bonded, frozen water molecules. In other words, clathrate hydrates are clathrate compounds in which the host molecule is water and the guest molecule is typically a gas or liquid. Without the support of the trapped molecules, the lattice structure of hydrate clathrates would collapse into conventional ice crystal structure or liquid water. Most low molecular weight gases, including O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe, as well as some higher hydrocarbons and freons, will form hydrates at suitable temperatures and pressures. Clathrate hydrates are not officially chemical compounds, as the enclathrated guest molecules are never bonded to the lattice. The formation and decomposition of clathrate hydrates are first order phase transitions, not chemical reactions. Their detailed formation and decomposition mechanisms on a molecular level are still not well understood. Clathrate hydrates were first documented in 1810 by Sir Humphry Davy who found that water was a primary component of what was earlier thought to be solidified chlorine.
Permafrost is soil or underwater sediment which continuously remains below 0 °C (32 °F) for two years or more: the oldest permafrost had been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below a meter (3 ft), the deepest is greater than 1,500 m (4,900 ft). Similarly, the area of individual permafrost zones may be limited to narrow mountain summits or extend across vast Arctic regions. The ground beneath glaciers and ice sheets is not usually defined as permafrost, so on land, permafrost is generally located beneath a so-called active layer of soil which freezes and thaws depending on the season.
A cold seep is an area of the ocean floor where seepage of fluids rich in hydrogen sulfide, methane, and other hydrocarbons occurs, often in the form of a brine pool. Cold does not mean that the temperature of the seepage is lower than that of the surrounding sea water; on the contrary, its temperature is often slightly higher. The "cold" is relative to the very warm conditions of a hydrothermal vent. Cold seeps constitute a biome supporting several endemic species.
A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word clathrate is derived from the Latin clathratus, meaning 'with bars, latticed'. Most clathrate compounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host–guest complexes and inclusion compounds. According to IUPAC, clathrates are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules." The term refers to many molecular hosts, including calixarenes and cyclodextrins and even some inorganic polymers such as zeolites.
A mud volcano or mud dome is a landform created by the eruption of mud or slurries, water and gases. Several geological processes may cause the formation of mud volcanoes. Mud volcanoes are not true igneous volcanoes as they do not produce lava and are not necessarily driven by magmatic activity. Mud volcanoes may range in size from merely 1 or 2 meters high and 1 or 2 meters wide, to 700 meters high and 10 kilometers wide. Smaller mud exudations are sometimes referred to as mud-pots.
The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature, as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years, and 25 times over 100 years. It is further proposed that these warming events caused the Bond Cycles and individual interstadial events, such as the Dansgaard–Oeschger interstadials.
Due to climate change in the Arctic, this polar region is expected to become "profoundly different" by 2050. The speed of change is "among the highest in the world", with the rate of warming being 3-4 times faster than the global average. This warming has already resulted in the profound Arctic sea ice decline, the accelerating melting of the Greenland ice sheet and the thawing of the permafrost landscape. These ongoing transformations are expected to be irreversible for centuries or even millennia.
Methane is a chemical compound with the chemical formula CH4. It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it is hard because it is a gas at standard temperature and pressure.
Arctic methane release is the release of methane from Arctic ocean floors, lake bottoms, wetlands and soils in permafrost regions of the Arctic. While it is a long-term natural process, methane release is exacerbated by global warming. This results in a positive climate change feedback, as methane is a powerful greenhouse gas. The Arctic region is one of many natural sources of methane. Climate change could accelerate methane release in the Arctic, due to the release of methane from existing stores, and from methanogenesis in rotting biomass. When permafrost thaws as a consequence of warming, large amounts of organic material can become available for methanogenesis and may ultimately be released as methane.
Climate change feedbacks are natural processes which impact how much global temperatures will increase for a given amount of greenhouse gas emissions. Positive feedbacks amplify global warming while negative feedbacks diminish it. Feedbacks influence both the amount of greenhouse gases in the atmosphere and the amount of temperature change that happens in response. While emissions are the forcing that causes climate change, feedbacks combine to control climate sensitivity to that forcing.
The permafrost carbon cycle or Arctic carbon cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0o C for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir, one which was often neglected in the initial research determining global terrestrial carbon reservoirs. Since the start of the 2000s, however, far more attention has been paid to the subject, with an enormous growth both in general attention and in the scientific research output.
Nankai Methane Hydrate Site is located in the Nankai Trough, Japan.
Hydrate Ridge is an accretionary thrust clathrate hydrate formation, meaning it has been made of sediment scraped off of subducting oceanic plate. It is approx. 200 m high, and located 100 km offshore of Oregon. At hydrate formations, methane is trapped in crystallized water structures. Such methane transforms into the gaseous phase and seeps into the ocean at this site, which has been a popular location of study since its discovery in 1986. Hydrate Ridge also supports a methane-driven benthic community.
Jeffrey Paul "Jeff" Chanton is the 2017-2018 Robert O. Lawton Distinguished Professor and John Widmer Winchester professor of oceanography at Florida State University. His research interests include Arctic methane release from the thawing of permafrost. Chanton co-created the Master of Science in aquatic environmental sciences at FSU with Nancy Marcus.
Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% of methane released globally was from human activities, while natural sources contributed about 40%. Reducing methane emissions by capturing and utilizing the gas can produce simultaneous environmental and economic benefits.
A gas hydrate pingo is a submarine dome structure formed by the accumulation of gas hydrates under the seafloor.
Methane reservoirs on Earth are mainly found in
Bottom simulating reflectors (BSRs) are, on seismic reflection profiles, shallow seismic reflection events, characterized by their reflection geometry similar to seafloor bathymetry. . They have, however, the opposite reflection polarity to the seabed reflection, and frequently intersect the primary reflections.
Marta E. Torres is a marine geologist known for her work on the geochemistry of cold seeps and methane hydrates. She is a professor at Oregon State University, and an elected fellow of the Geochemical Society and the Geological Society of America.