Clathrate gun hypothesis

Meteorological hypothesis

Methane clathrate is released as gas into the surrounding water column or soils when ambient temperature increases.

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 (33 when accounting for aerosol interactions).[1] It is further proposed that these warming events caused the Bond cycles and individual interstadial events, such as the Dansgaard–Oeschger interstadials.[2]

The hypothesis was supported for the Bølling–Allerød warming and Preboreal periods, but not for Dansgaard–Oeschger interstadials,[3] although there are still debates on the topic.[4] While it may be important on the millennial timescales,[5][6] it is no longer considered relevant for the near future climate change: the IPCC Sixth Assessment Report states "It is very unlikely that gas clathrates (mostly methane) in deeper terrestrial permafrost and subsea clathrates will lead to a detectable departure from the emissions trajectory during this century".[7]

## Mechanism

[edit]

Specific structure of a gas hydrate piece, from the subduction zone off Oregon Gas hydrate-bearing sediment, from the subduction zone off Oregon

Methane clathrate, also known commonly as methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure. Potentially large deposits of methane clathrate have been found under sediments on the ocean floors of the Earth, although the estimates of total resource size given by various experts differ by many orders of magnitude, leaving doubt as to the size of methane clathrate deposits (particularly in the viability of extracting them as a fuel resource). Indeed, cores of greater than 10 centimeters' contiguous depth had only been found in three sites as of 2000, and some resource reserve size estimates for specific deposits/locations have been based primarily on seismology.[8][9] The sudden release of large amounts of natural gas from methane clathrate deposits in runaway climate change could be a cause of past, future, and present climate changes.

In the Arctic Ocean, clathrates can exist in shallower water stabilized by lower temperatures rather than higher pressures; these may potentially be marginally stable much closer to the surface of the sea-bed, stabilized by a frozen 'lid' of permafrost preventing methane escape. The so-called self-preservation phenomenon has been studied by Russian geologists starting in the late 1980s.[10] This metastable clathrate state can be a basis for release events of methane excursions, such as during the interval of the Last Glacial Maximum.[11] A study from 2010 concluded with the possibility for a trigger of abrupt climate warming based on metastable methane clathrates in the East Siberian Arctic Shelf (ESAS) region.[12]

## Possible past releases

[edit]

Gas-hydrate deposits by sector[13]

Studies published in 2000 considered this hypothetical effect to be responsible for warming events in and at the end of the Last Glacial Maximum.[14] Although periods of increased atmospheric methane match periods of continental-slope failure,[3][4] later work found that the distinct deuterium/hydrogen (D/H) isotope ratio indicated that wetland methane emissions was the main contributor to atmospheric methane concentrations.[15][16] While there were major dissociation events during the last deglaciation, with Bølling–Allerød warming triggering the disappearance of the entire methane hydrate deposit in the Barents Sea within 5000 years, those events failed to counteract the onset of a major Younger Dryas cooling period, suggesting that most of the methane stayed within the seawater after being liberated from the seafloor deposits, with very little entering the atmosphere.[17][18]

In 2008, it was suggested that equatorial permafrost methane clathrate may have had a role in the sudden warm-up of "Snowball Earth", 630 million years ago.[19]

Other events potentially linked to methane hydrate excursions are the Permian–Triassic extinction event and the Paleocene–Eocene Thermal Maximum.

### Paleocene–Eocene Thermal Maximum

[edit]

This section is an excerpt from Paleocene–Eocene Thermal Maximum.[edit]

Climate change during the last 65 million years as expressed by the oxygen isotope composition of benthic foraminifera. The Paleocene-Eocene thermal maximum (PETM) is characterized by a brief but prominent excursion, attributed to rapid warming. Note that the excursion is understated in this graph due to the smoothing of data.

The Paleocene–Eocene thermal maximum (PETM), alternatively ”Eocene thermal maximum 1 (ETM1)“ and formerly known as the "Initial Eocene" or “Late Paleocene thermal maximum", was a geologically brief time interval characterized by a 5–8 °C global average temperature rise and massive input of carbon into the ocean and atmosphere.[20][21] The event began, now formally codified, at the precise time boundary between the Paleocene and Eocene geological epochs.[22] The exact age and duration of the PETM remain uncertain, but it occurred around 55.8 million years ago (Ma) and lasted about 200 thousand years (Ka).[23][24]

The PETM arguably represents our best past analogue for which to understand how global warming and the carbon cycle operate in a greenhouse world.[21][25][26] The time interval is marked by a prominent negative excursion in carbon stable isotope (δ13C) records from around the globe; more specifically, a large decrease in the 13C/12C ratio of marine and terrestrial carbonates and organic carbon has been found and correlated across hundreds of locations.[21][27][28] The magnitude and timing of the PETM (δ13C) excursion, which attest to the massive past carbon release to our ocean and atmosphere, and the source of this carbon remain topics of considerable current geoscience research.

What has become clear over the last few decades: Stratigraphic sections across the PETM reveal numerous changes beyond warming and carbon emission.[21] Consistent with an Epoch boundary, Fossil records of many organisms show major turnovers. In the marine realm, a mass extinction of benthic foraminifera, a global expansion of subtropical dinoflagellates, and an appearance of excursion taxa, including within planktic foraminifera planktic foraminifera and calcareous nannofossils, all occurred during the beginning stages of the PETM. On land, many modern mammal orders (including primates) suddenly appear in Europe and in North America.[29]

In order for the clathrate hypothesis to be applicable to PETM, the oceans must show signs of having been warmer slightly before the carbon isotope excursion, because it would take some time for the methane to become mixed into the system and δ13C-reduced carbon to be returned to the deep ocean sedimentary record. Up until the 2000s, the evidence suggested that the two peaks were in fact simultaneous, weakening the support for the methane theory. In 2002, a short gap between the initial warming and the δ13C excursion was detected.[30] In 2007, chemical markers of surface temperature (TEX86) had also indicated that warming occurred around 3,000 years before the carbon isotope excursion, although this did not seem to hold true for all cores.[31] However, research in 2005 found no evidence of this time gap in the deeper (non-surface) waters.[32] Moreover, the small apparent change in TEX86 that precede the δ13C anomaly can easily (and more plausibly) be ascribed to local variability (especially on the Atlantic coastal plain, e.g. Sluijs, et al., 2007) as the TEX86 paleo-thermometer is prone to significant biological effects. The δ18O of benthic or planktonic forams does not show any pre-warming in any of these localities, and in an ice-free world, it is generally a much more reliable indicator of past ocean temperatures. Analysis of these records reveals another interesting fact: planktonic (floating) forams record the shift to lighter isotope values earlier than benthic (bottom dwelling) forams.[33] The lighter (lower δ13C) methanogenic carbon can only be incorporated into foraminifer shells after it has been oxidised. A gradual release of the gas would allow it to be oxidised in the deep ocean, which would make benthic foraminifera show lighter values earlier. The fact that the planktonic foraminifera are the first to show the signal suggests that the methane was released so rapidly that its oxidation used up all the oxygen at depth in the water column, allowing some methane to reach the atmosphere unoxidised, where atmospheric oxygen would react with it. This observation also allows us to constrain the duration of methane release to under around 10,000 years.[30]

However, there are several major problems with the methane hydrate dissociation hypothesis. The most parsimonious interpretation for surface-water foraminifera to show the δ13C excursion before their benthic counterparts (as in the Thomas et al. paper) is that the perturbation occurred from the top down, and not the bottom up. If the anomalous δ13C (in whatever form: CH4 or CO2) entered the atmospheric carbon reservoir first, and then diffused into the surface ocean waters, which mix with the deeper ocean waters over much longer time-scales, we would expect to observe the planktonics shifting toward lighter values before the benthics.[34]

An additional critique of the methane clathrate release hypothesis is that the warming effects of large-scale methane release would not be sustainable for more than a millennium. Thus, exponents of this line of criticism suggest that methane clathrate release could not have been the main driver of the PETM, which lasted for 50,000 to 200,000 years.[35]

There has been some debate about whether there was a large enough amount of methane hydrate to be a major carbon source; a 2011 paper proposed that was the case.[36] The present-day global methane hydrate reserve was once considered to be between 2,000 and 10,000 Gt C (billions of tons of carbon), but is now estimated between 1500 and 2000 Gt C.[37] However, because the global ocean bottom temperatures were ~6 °C higher than today, which implies a much smaller volume of sediment hosting gas hydrate than today, the global amount of hydrate before the PETM has been thought to be much less than present-day estimates.[35] One study, however, suggests that because seawater oxygen content was lower, sufficient methane clathrate deposits could have been present to make them a viable mechanism for explaining the isotopic changes.[38] In a 2006 study, scientists regarded the source of carbon for the PETM to be a mystery.[39] A 2011 study, using numerical simulations suggests that enhanced organic carbon sedimentation and methanogenesis could have compensated for the smaller volume of hydrate stability.[36] A 2016 study based on reconstructions of atmospheric CO2 content during the PETM's carbon isotope excursions (CIE), using triple oxygen isotope analysis, suggests a massive release of seabed methane into the atmosphere as the driver of climatic changes. The authors also state that a massive release of methane hydrates through thermal dissociation of methane hydrate deposits has been the most convincing hypothesis for explaining the CIE ever since it was first identified, according to them.[40] In 2019, a study suggested that there was a global warming of around 2 degrees several millennia before PETM, and that this warming had eventually destabilized methane hydrates and caused the increased carbon emission during PETM, as evidenced by the large increase in barium ocean concentrations (since PETM-era hydrate deposits would have been also been rich in barium, and would have released it upon their meltdown).[41] In 2022, a foraminiferal records study had reinforced this conclusion, suggesting that the release of CO2 before PETM was comparable to the current anthropogenic emissions in its rate and scope, to the point that there was enough time for a recovery to background levels of warming and ocean acidification in the centuries to millennia between the so-called pre-onset excursion (POE) and the main event (carbon isotope excursion, or CIE).[42] A 2021 paper had further indicated that while PETM began with a significant intensification of volcanic activity and that lower-intensity volcanic activity sustained elevated carbon dioxide levels, "at least one other carbon reservoir released significant greenhouse gases in response to initial warming".[43]

It was estimated in 2001 that it would take around 2,300 years for an increased temperature to diffuse warmth into the sea bed to a depth sufficient to cause a release of clathrates, although the exact time-frame is highly dependent on a number of poorly constrained assumptions.[44] Ocean warming due to flooding and pressure changes due to a sea-level drop may have caused clathrates to become unstable and release methane. This can take place over as short of a period as a few thousand years. The reverse process, that of fixing methane in clathrates, occurs over a larger scale of tens of thousands of years.[45]

### Permian–Triassic extinction event

[edit]

This section is an excerpt from Permian–Triassic extinction event.[edit]

Marine extinction intensity during Phanerozoic

Millions of years ago

(H)

K–Pg

Tr–J

P–Tr

Cap

Late D

O–S

Plot of extinction intensity (percentage of marine genera that are present in each interval of time but do not exist in the following interval) vs time in the past.[46] Geological periods are annotated (by abbreviation and colour) above. The Permian–Triassic extinction event is the most significant event for marine genera, with just over 50% (according to this source) perishing. (source and image info)

Permian–Triassic boundary at Frazer Beach in New South Wales, with the End Permian extinction event located just above the coal layer[47]

The Permian–Triassic extinction event (also known as the P–T extinction event, the Late Permian extinction event,[48] the Latest Permian extinction event,[49] the End-Permian extinction event,[50][51] and colloquially as the Great Dying,[52][53]) was an extinction event that occurred approximately 251.9 million years ago, at the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras.[54] It is Earth's most severe known extinction event,[55][56] with the extinction of 57% of biological families, 62% of genera and 81% of marine species[57][58][59] (previous estimates of 90-96% marine species extinction were due to historical conflation with the end-Capitanian mass extinction which occurred 7-10 million years earlier[57]) and 70% of terrestrial vertebrate species.[60] It is also the greatest known mass extinction of insects.[61] It is the greatest of the "Big Five" mass extinctions of the Phanerozoic.[62] There is evidence for one to three distinct pulses, or phases, of extinction.[60][63]

The scientific consensus is that the main cause of the extinction was the flood basalt volcanic eruptions that created the Siberian Traps,[64][65] which released sulfur dioxide and carbon dioxide, resulting in euxinia (oxygen-starved, sulfurous oceans),[66][67] elevated global temperatures,[68][69][70] and acidified oceans.[71][72][48] The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system during this period.[68] Several other contributing factors have been proposed, including the emission of carbon dioxide from the burning of oil and coal deposits ignited by the eruptions;[73][74]

emissions of methane from the gasification of methane clathrates;[75] emissions of methane by novel methanogenic microorganisms nourished by minerals dispersed in the eruptions;[76][77][78] longer and more intense El Niño events;[79] and an extraterrestrial impact which created the Araguainha crater and caused seismic release of methane[80][81][82] and the destruction of the ozone layer with increased exposure to solar radiation.[83][84][85]

Massive release of methane from these clathrates may have contributed to the PTME, as scientists have found worldwide evidence of a swift decrease of about 1% in the 13C ⁄ 12C ratio in carbonate rocks from the end-Permian.[86][87] This is the first, largest, and fastest of a series of excursions (decreases and increases) in the ratio, until it abruptly stabilised in the middle Triassic, followed soon afterwards by the recovery of calcifying shelled sealife.[88] The seabed probably contained methane hydrate deposits, and the lava caused the deposits to dissociate, releasing vast quantities of methane.[89] A vast release of methane might cause significant global warming since methane is a very powerful greenhouse gas. Strong evidence suggests the global temperatures increased by about 6 °C (10.8 °F) near the equator and therefore by more at higher latitudes: a sharp decrease in oxygen isotope ratios (18O ⁄ 16O);[90] the extinction of Glossopteris flora (Glossopteris and plants that grew in the same areas), which needed a cold climate, with its replacement by floras typical of lower paleolatitudes.[91] It was also suggested that a large-scale release of methane and other greenhouse gases from the ocean into the atmosphere was connected to the anoxic events and euxinic (sulfidic) events at the time, with the exact mechanism compared to the 1986 Lake Nyos disaster.[92]

The clathrate hypothesis seemed the only proposed mechanism sufficient to cause a global 1% reduction in the  13C ⁄ 12C ratio .[93][94] While a variety of factors may have contributed to the ratio drop, a 2002 review found most of them insufficient to account for the observed amount:[75]

* Gases from volcanic eruptions have a 13C ⁄ 12C ratio about 0.5 to 0.8% below standard (δ13C −0.5 to −0.8%), but a 1995 assessment concluded that the observed 1.0% worldwide reduction would have required eruptions massively larger than any found.[95] (However, this analysis addressed only CO2 produced by the magma itself, not from interactions with carbon bearing sediments, as described below.)
* A reduction in organic activity would extract 12C more slowly from the environment and leave more of it to be incorporated into sediments, thus reducing the 13C ⁄ 12C ratio.  Biochemical processes preferentially use the lighter isotopes since chemical reactions are ultimately driven by electromagnetic forces between atoms and lighter isotopes respond more quickly to these forces, but a study of a smaller drop of 0.3 to 0.4% in  13C ⁄ 12C  (δ13C −3 to −4 ‰) at the Paleocene-Eocene Thermal Maximum (PETM) concluded that even transferring all the organic carbon (in organisms, soils, and dissolved in the ocean) into sediments would be insufficient: Even such a large burial of material rich in 12C would not have produced the 'smaller' drop in the  13C ⁄ 12C ratio  of the rocks around the PETM.[95]
* Buried sedimentary organic matter has a  13C ⁄ 12C ratio  2.0 to 2.5% below normal (δ13C −2.0 to −2.5%). Theoretically, if the sea level fell sharply, shallow marine sediments would be exposed to oxidation. But 6,500–8,400 gigatonnes (1 gigatonne = 1012 kg) of organic carbon would have to be oxidized and returned to the ocean-atmosphere system within less than a few hundred thousand years to reduce the  13C ⁄ 12C ratio  by 1.0%, which is not thought to be a realistic possibility.[94] Moreover, sea levels were rising rather than falling at the time of the extinction.[96]
* Rather than a sudden decline in sea level, intermittent periods of ocean-bottom hyperoxia and anoxia (high-oxygen and low- or zero-oxygen conditions) may have caused the  13C ⁄ 12C ratio  fluctuations in the Early Triassic;[88] and global anoxia may have been responsible for the end-Permian blip. The continents of the end-Permian and early Triassic were more clustered in the tropics than they are now, and large tropical rivers would have dumped sediment into smaller, partially enclosed ocean basins at low latitudes. Such conditions favor oxic and anoxic episodes; oxic/anoxic conditions would result in a rapid release/burial, respectively, of large amounts of organic carbon, which has a low  13C ⁄ 12C ratio  because biochemical processes use the lighter isotopes more.[97] That or another organic-based reason may have been responsible for both that and a late Proterozoic/Cambrian pattern of fluctuating  13C ⁄ 12C ratios.[88]

However, the clathrate hypothesis has also been criticized. Carbon-cycle models which include consideration of roasting carbonate sediments by volcanism confirm that it would have had enough effect to produce the observed reduction.[75][98] Also, the pattern of isotope shifts expected to result from a massive release of methane does not match the patterns seen throughout the Early Triassic. Not only would such a cause require the release of five times as much methane as postulated for the PETM, but would it also have to be reburied at an unrealistically high rate to account for the rapid increases in the  13C ⁄ 12C ratio  (episodes of high positive δ13C) throughout the early Triassic before it was released several times again.[88] The latest research suggests that greenhouse gas release during the extinction event was dominated by volcanic carbon dioxide,[99] and while methane release had to have contributed, isotopic signatures show that thermogenic methane released from the Siberian Traps had consistently played a larger role than methane from clathrates and any other biogenic sources such as wetlands during the event.[68]

Adding to the evidence against methane clathrate release as the central driver of warming, the main rapid warming event is also associated with marine transgression rather than regression; the former would not normally have initiated methane release, which would have instead required a decrease in pressure, something that would be generated by a retreat of shallow seas.[100] The configuration of the world's landmasses into one supercontinent would also mean that the global gas hydrate reservoir was lower than today, further damaging the case for methane clathrate dissolution as a major cause of the carbon cycle disruption.[101]

## Climate change feedback

[edit]

Main article: Climate change in the Arctic

### Modern deposits

[edit]

Most deposits of methane clathrate are in sediments too deep to respond rapidly,[102] and 2007 modelling by Archer suggests that the methane forcing derived from them should remain a minor component of the overall greenhouse effect.[103] Clathrate deposits destabilize from the deepest part of their stability zone, which is typically hundreds of metres below the seabed. A sustained increase in sea temperature will warm its way through the sediment eventually, and cause the shallowest, most marginal clathrate to start to break down; but it will typically take on the order of a thousand years or more for the temperature change to get that far into the seabed.[103] Further, subsequent research on midlatitude deposits in the Atlantic and Pacific Ocean found that any methane released from the seafloor, no matter the source, fails to reach the atmosphere once the depth exceeds 430 m (1,411 ft), while geological characteristics of the area make it impossible for hydrates to exist at depths shallower than 550 m (1,804 ft).[104][105]

Potential Methane release in the Eastern Siberian Arctic Shelf

However, some methane clathrates deposits in the Arctic are much shallower than the rest, which could make them far more vulnerable to warming. A trapped gas deposit on the continental slope off Canada in the Beaufort Sea, located in an area of small conical hills on the ocean floor is just 290 m (951 ft) below sea level and considered the shallowest known deposit of methane hydrate.[106] However, the East Siberian Arctic Shelf averages 45 meters in depth, and it is assumed that below the seafloor, sealed by sub-sea permafrost layers, hydrates deposits are located.[107][108] This would mean that when the warming potentially talik or pingo-like features within the shelf, they would also serve as gas migration pathways for the formerly frozen methane, and a lot of attention has been paid to that possibility.[109][110][111] Shakhova et al. (2008) estimate that not less than 1,400 gigatonnes of carbon is presently locked up as methane and methane hydrates under the Arctic submarine permafrost, and 5–10% of that area is subject to puncturing by open talik. Their paper initially included the line that the "release of up to 50 gigatonnes of predicted amount of hydrate storage [is] highly possible for abrupt release at any time". A release on this scale would increase the methane content of the planet's atmosphere by a factor of twelve,[112][113] equivalent in greenhouse effect to a doubling in the 2008 level of CO2.

This is what led to the original Clathrate gun hypothesis, and in 2008 the United States Department of Energy National Laboratory system[114] and the United States Geological Survey's Climate Change Science Program both identified potential clathrate destabilization in the Arctic as one of four most serious scenarios for abrupt climate change, which have been singled out for priority research. The USCCSP released a report in late December 2008 estimating the gravity of this risk.[115] A 2012 study of the effects for the original hypothesis, based on a coupled climate–carbon cycle model (GCM) assessed a 1000-fold (from <1 to 1000 ppmv) methane increase—within a single pulse, from methane hydrates (based on carbon amount estimates for the PETM, with ~2000 GtC), and concluded it would increase atmospheric temperatures by more than 6 °C within 80 years. Further, carbon stored in the land biosphere would decrease by less than 25%, suggesting a critical situation for ecosystems and farming, especially in the tropics.[116] Another 2012 assessment of the literature identifies methane hydrates on the Shelf of East Arctic Seas as a potential trigger.[117]

A risk of seismic activity being potentially responsible for mass methane releases has been considered as well. In 2012, seismic observations destabilizing methane hydrate along the continental slope of the eastern United States, following the intrusion of warmer ocean currents, suggests that underwater landslides could release methane. The estimated amount of methane hydrate in this slope is 2.5 gigatonnes (about 0.2% of the amount required to cause the PETM), and it is unclear if the methane could reach the atmosphere. However, the authors of the study caution: "It is unlikely that the western North Atlantic margin is the only area experiencing changing ocean currents; our estimate of 2.5 gigatonnes of destabilizing methane hydrate may therefore represent only a fraction of the methane hydrate currently destabilizing globally."[118] Bill McGuire notes, "There may be a threat of submarine landslides around the margins of Greenland, which are less well explored. Greenland is already uplifting, reducing the pressure on the crust beneath and also on submarine methane hydrates in the sediment around its margins, and increased seismic activity may be apparent within decades as active faults beneath the ice sheet are unloaded. This could provide the potential for the earthquake or methane hydrate destabilisation of submarine sediment, leading to the formation of submarine slides and, perhaps, tsunamis in the North Atlantic."[119]

### Observed emissions

[edit]

#### East Siberian Arctic Shelf

[edit]

Methane releases in Laptev Sea are typically consumed within the sediment by methanotrophs. Areas with high sedimentation (top) subject their microbial communities to continual disturbance, and so they are the most likely to see active fluxes, whether with (right) or without active upward flow (left). Even so, the annual release may be limited to 1000 tonnes or less.[120]

Research carried out in 2008 in the Siberian Arctic showed methane releases on the annual scale of millions of tonnes, which was a substantial increase on the previous estimate of 0.5 millions of tonnes per year.[121] apparently through perforations in the seabed permafrost,[111] with concentrations in some regions reaching up to 100 times normal levels.[122][123] The excess methane has been detected in localized hotspots in the outfall of the Lena River and the border between the Laptev Sea and the East Siberian Sea. At the time, some of the melting was thought to be the result of geological heating, but more thawing was believed to be due to the greatly increased volumes of meltwater being discharged from the Siberian rivers flowing north.[124]

By 2013, the same team of researchers used multiple sonar observations to quantify the density of bubbles emanating from subsea permafrost into the ocean (a process called ebullition), and found that 100–630 mg methane per square meter is emitted daily along the East Siberian Arctic Shelf (ESAS), into the water column. They also found that during storms, when wind accelerates air-sea gas exchange, methane levels in the water column drop dramatically. Observations suggest that methane release from seabed permafrost will progress slowly, rather than abruptly. However, Arctic cyclones, fueled by global warming, and further accumulation of greenhouse gases in the atmosphere could contribute to more rapid methane release from this source. Altogether, their updated estimate had now amounted to 17 millions of tonnes per year.[125]

However, these findings were soon questioned, as this rate of annual release would mean that the ESAS alone would account for between 28% and 75% of the observed Arctic methane emissions, which contradicts many other studies. In January 2020, it was found that the rate at which methane enters the atmosphere after it had been released from the shelf deposits into the water column had been greatly overestimated, and observations of atmospheric methane fluxes taken from multiple ship cruises in the Arctic instead indicate that only around 3.02 million tonnes of methane are emitted annually from the ESAS.[126] A modelling study published in 2020 suggested that under the present-day conditions, annual methane release from the ESAS may be as low as 1000 tonnes, with 2.6 – 4.5 million tonnes representing the peak potential of turbulent emissions from the shelf.[120]

#### Beaufort Sea continental slope

[edit]

Profile illustrating the continental shelf, slope and rise

A radiocarbon dating study in 2018 found that after the 30-meter isobath, only around 10% of the methane in surface waters can be attributed to ancient permafrost or methane hydrates. The authors suggested that even a significantly accelerated methane release would still largely fail to reach the atmosphere.[127]

#### Svalbard

[edit]

Hong et al. (2017) studied methane seepage in the shallow arctic seas at the Barents Sea close to Svalbard. Temperature at the seabed has fluctuated seasonally over the last century, between −1.8 °C (28.8 °F) and 4.8 °C (40.6 °F), it has only affected release of methane to a depth of about 1.6 meters at the sediment-water interface. Hydrates can be stable through the top 60 meters of the sediments and the current observed releases originate from deeper below the sea floor. They conclude that the increased methane flux started hundreds to thousands of years ago, noted about it, "..episodic ventilation of deep reservoirs rather than warming-induced gas hydrate dissociation."[128] Summarizing his research, Hong stated:

> The results of our study indicate that the immense seeping found in this area is a result of natural state of the system. Understanding how methane interacts with other important geological, chemical and biological processes in the Earth system is essential and should be the emphasis of our scientific community.[129]

Methane releases specifically attributed to hydrate dissociation in the Svalbard appear to be much lower than the leaks from other methane sources.[130]

Research by Wallmann et al. (2018) concluded that hydrate dissociation at Svalbard 8,000 years ago was due to isostatic rebound (continental uplift following deglaciation). As a result, the water depth got shallower with less hydrostatic pressure, without further warming. The study, also found that today's deposits at the site become unstable at a depth of ~ 400 meters, due to seasonal bottom water warming, and it remains unclear if this is due to natural variability or anthropogenic warming.[130] Moreover, another paper published in 2017 found that only 0.07% of the methane released from the gas hydrate dissociation at Svalbard appears to reach the atmosphere, and usually only when the wind speeds were low.[131] In 2020, a subsequent study confirmed that only a small fraction of methane from the Svalbard seeps reaches the atmosphere, and that the wind speed holds a greater influence on the rate of release than dissolved methane concentration on site.[132]

Finally, a paper published in 2017 indicated that the methane emissions from at least one seep field at Svalbard were more than compensated for by the enhanced carbon dioxide uptake due to the greatly increased phytoplankton activity in this nutrient-rich water. The daily amount of carbon dioxide absorbed by the phytoplankton was 1,900 greater than the amount of methane emitted, and the negative (i.e. indirectly cooling) radiative forcing from the CO2 uptake was up to 251 times greater than the warming from the methane release.[133]

### Current outlook

[edit]

In 2014 based on their research on the northern United States Atlantic marine continental margins from Cape Hatteras to Georges Bank, a group of scientists from the US Geological Survey, the Department of Geosciences, Mississippi State University, Department of Geological Sciences, Brown University and Earth Resources Technology, found widespread leakage of methane from the seafloor, but they did not assign specific dates, beyond suggesting that some of the seeps were more than 1000 years old.[134][135] In March 2017, a meta-analysis by the USGS Gas Hydrates Project concluded:[136][13]

> Our review is the culmination of nearly a decade of original research by the USGS, my coauthor Professor John Kessler at the University of Rochester, and many other groups in the community," said USGS geophysicist Carolyn Ruppel, who is the paper's lead author and oversees the USGS Gas Hydrates Project. "After so many years spent determining where gas hydrates are breaking down and measuring methane flux at the sea-air interface, we suggest that conclusive evidence for release of hydrate-related methane to the atmosphere is lacking.

In June 2017, scientists from the Center for Arctic Gas Hydrate (CAGE), Environment and Climate at the University of Tromsø, published a study 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. These areas around the Barents Sea, still seep methane today, and still existing bulges with methane reservoirs could eventually have the same fate.[137] Later that same year, the Arctic Council published SWIPA 2017 report, where it cautioned "Arctic sources and sinks of greenhouse gases are still hampered by data and knowledge gaps."[138]

In 2018, a perspective piece devoted to tipping points in the climate system suggested that the climate change contribution from methane hydrates would be "negligible" by the end of the century, but could amount to 0.4–0.5 °C (0.72–0.90 °F) on the millennial timescales.[6] In 2021, the IPCC Sixth Assessment Report no longer included methane hydrates in the list of potential tipping points, and says that "it is very unlikely that CH4 emissions from clathrates will substantially warm the climate system over the next few centuries."[7] The report had also linked terrestrial hydrate deposits to gas emission craters discovered in the Yamal Peninsula in Siberia, Russia beginning in July 2014,[139] but noted that since terrestrial gas hydrates predominantly form at a depth below 200 meters, a substantial response within the next few centuries can be ruled out.[7] Likewise, a 2022 assessment of tipping points described methane hydrates as a "threshold-free feedback" rather than a tipping point.[140][141]

## In fiction

[edit]

* The science fiction novel Mother of Storms by John Barnes offers a fictional example of catastrophic climate change caused by methane clathrate release.
* In The Life Lottery by Ian Irvine unprecedented seismic activity triggers a release of methane hydrate, reversing global cooling.
* The hypothesis is the basis of an experiment in the PlayStation 2 game Death By Degrees.
* In Transcendent by Stephen Baxter, averting such a crisis is a major plotline.
* The novel The Black Silent by author David Dun features this idea as a key scientific point.
* In the anime Ergo Proxy, a string of explosions in the methane hydrate reserves wipes out 85% of species on Earth.
* The novel The Far Shore of Time by Frederik Pohl features an alien race attempting to destroy humanity by bombing the methane clathrate reserves, thus releasing the gas into the atmosphere.
* The novel The Swarm by Frank Schätzing features what first appear to be freak events related to the world's oceans.
* In Charles Stross' Laundry Files universe, an intentionally triggered clathrate gun scenario is viewed as a possible retaliatory strategy that could be utilized by Blue Hades in response to terminal violation of the Benthic Treaty.

## See also

[edit]

* Atlantic meridional overturning circulation
* Azolla event
* Clathrate compound
* Effects of climate change
* Extinction event
* Limnic eruption
* Methane chimney
* Ocean acidification
* Storegga Slide

## References

[edit]

1. ^ Shindell, Drew T.; Faluvegi, Greg; Koch, Dorothy M.; Schmidt, Gavin A.; Unger, Nadine; Bauer, Susanne E. (2009). "Improved attribution of climate forcing to emissions". Science. 326 (5953): 716–718\. Bibcode:2009Sci...326..716S. doi:10.1126/science.1174760. PMID 19900930. S2CID 30881469.
2. ^ Kennett, James P.; Cannariato, Kevin G.; Hendy, Ingrid L.; Behl, Richard J. (2003). Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. Washington DC: American Geophysical Union. doi:10.1029/054SP. ISBN 978-0-87590-296-8.
3. ^ a b Maslin, M; Owen, M; Day, S; Long, D (2004). "Linking continental-slope failures and climate change: Testing the clathrate gun hypothesis". Geology. 32 (1): 53–56\. Bibcode:2004Geo....32...53M. doi:10.1130/G20114.1. ISSN 0091-7613.
4. ^ a b Maslin, M; Owen, M; Betts, R; Day, S; Dunkley Jones, T; Ridgwell, A (2010-05-28). "Gas hydrates: past and future geohazard?". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 368 (1919): 2369–2393\. Bibcode:2010RSPTA.368.2369M. doi:10.1098/rsta.2010.0065. ISSN 1364-503X. PMID 20403833. S2CID 24574034.
5. ^ Archer, David; Buffett, Bruce (2005). "Time-dependent response of the global ocean clathrate reservoir to climatic and anthropogenic forcing" (PDF). Geochemistry, Geophysics, Geosystems. 6 (3): 1–13\. Bibcode:2005GGG.....6.3002A. doi:10.1029/2004GC000854. Archived (PDF) from the original on 2009-07-09. Retrieved 2009-05-15.
6. ^ a b Schellnhuber, Hans Joachim; Winkelmann, Ricarda; Scheffer, Marten; Lade, Steven J.; Fetzer, Ingo; Donges, Jonathan F.; Crucifix, Michel; Cornell, Sarah E.; Barnosky, Anthony D. (2018). "Trajectories of the Earth System in the Anthropocene". Proceedings of the National Academy of Sciences. 115 (33): 8252–8259\. Bibcode:2018PNAS..115.8252S. doi:10.1073/pnas.1810141115. ISSN 0027-8424. PMC 6099852. PMID 30082409.
7. ^ a b c Fox-Kemper, B.; Hewitt, H.T.; Xiao, C.; Aðalgeirsdóttir, G.; Drijfhout, S.S.; Edwards, T.L.; Golledge, N.R.; Hemer, M.; Kopp, R.E.; Krinner, G.; Mix, A. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S.L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). "Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks" (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA: 5. doi:10.1017/9781009157896.011.
8. ^ Collet, Timothy S.; Kuuskraa, Vello A. (1998). "Hydrates contain vast store of world gas resources". Oil and Gas Journal. 96 (19): 90–95.(subscription required)
9. ^ Laherrere, Jean (May 3, 2000). "Oceanic Hydrates: More Questions Than Answers". Energy Exploration & Exploitation. 18 (4): 349–383\. Bibcode:2000EExEx..18..349L. doi:10.1260/0144598001492175. ISSN 0144-5987. S2CID 129242950.
10. ^ Istomin, V. A.; Yakushev, V. S.; Makhonina, N. A.; Kwon, V. G.; Chuvilin, E. M. (2006). "Self-preservation phenomenon of gas hydrates". Gas Industry of Russia (4). Archived from the original on 2013-12-03. Retrieved 2013-08-30.
11. ^ Buffett, Bruce A.; Zatsepina, Olga Y. (1999), "Metastability of gas hydrate", Geophysical Research Letters, 26 (19): 2981–2984, Bibcode:1999GeoRL..26.2981B, doi:10.1029/1999GL002339, S2CID 140711756
12. ^ Shakhova, Natalia; Semiletov, Igor; Salyuk, Anatoly; Yusupov, Vladimir; Kosmach, Denis; Gustafsson, Örjan (2010), "Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf", Science, 327 (5970): 1246–50, Bibcode:2010Sci...327.1246S, CiteSeerX 10.1.1.374.5869, doi:10.1126/science.1182221, PMID 20203047, S2CID 206523571
13. ^ a b Ruppel, Carolyn D.; Kessler, John D. (2017-03-31). "The interaction of climate change and methane hydrates: Climate-Hydrates Interactions". Reviews of Geophysics. 55 (1): 126–168\. Bibcode:2017RvGeo..55..126R. doi:10.1002/2016RG000534. hdl:1912/8978.
14. ^ Kennett, James P.; Cannariato, Kevin G.; Hendy, Ingrid L.; Behl, Richard J. (7 April 2000). "Carbon Isotopic Evidence for Methane Hydrate Instability During Quaternary Interstadials". Science. 288 (5463): 128–133\. Bibcode:2000Sci...288..128K. doi:10.1126/science.288.5463.128. PMID 10753115.
15. ^ Sowers, Todd (10 February 2006). "Late Quaternary Atmospheric CH
4 Isotope Record Suggests Marine Clathrates Are Stable". Science. 311 (5762): 838–840\. Bibcode:2006Sci...311..838S. doi:10.1126/science.1121235. PMID 16469923. S2CID 38790253.CH4+Isotope+Record+Suggests+Marine+Clathrates+Are+Stable&rft.volume=311&rft.issue=5762&rft.pages=838-840&rft.date=2006-02-10&rft_id=info:doi/10.1126/science.1121235&rft_id=https://api.semanticscholar.org/CorpusID:38790253#id-name=S2CID&rft_id=info:pmid/16469923&rft_id=info:bibcode/2006Sci...311..838S&rft.aulast=Sowers&rft.aufirst=Todd&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
16. ^ Severinghaus, Jeffrey P.; Whiticar, MJ; Brook, EJ; Petrenko, VV; Ferretti, DF; Severinghaus, JP (25 August 2006). "Ice Record of 13
C for Atmospheric CH
4 Across the Younger Dryas-Preboreal Transition". Science. 313 (5790): 1109–12\. Bibcode:2006Sci...313.1109S. doi:10.1126/science.1126562. PMID 16931759. S2CID 23164904.13C+for+Atmospheric+CH4+Across+the+Younger+Dryas-Preboreal+Transition&rft.volume=313&rft.issue=5790&rft.pages=1109-12&rft.date=2006-08-25&rft_id=info:doi/10.1126/science.1126562&rft_id=https://api.semanticscholar.org/CorpusID:23164904#id-name=S2CID&rft_id=info:pmid/16931759&rft_id=info:bibcode/2006Sci...313.1109S&rft.aulast=Severinghaus&rft.aufirst=Jeffrey+P.&rft.au=Whiticar,+MJ&rft.au=Brook,+EJ&rft.au=Petrenko,+VV&rft.au=Ferretti,+DF&rft.au=Severinghaus,+JP&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
17. ^ "Like 'champagne bottles being opened': Scientists document an ancient Arctic methane explosion". The Washington Post. June 1, 2017.
18. ^ Serov; et al. (2017). "Postglacial response of Arctic Ocean gas hydrates to climatic amelioration". PNAS. 114 (24): 6215–6220\. Bibcode:2017PNAS..114.6215S. doi:10.1073/pnas.1619288114. PMC 5474808. PMID 28584081.
19. ^ Kennedy, Martin; Mrofka, David; Von Der Borch, Chris (2008). "Snowball Earth termination by destabilization of equatorial permafrost methane clathrate" (PDF). Nature. 453 (7195): 642–645\. Bibcode:2008Natur.453..642K. doi:10.1038/nature06961. PMID 18509441. S2CID 4416812.
20. ^ Haynes, Laura L.; Hönisch, Bärbel (14 September 2020). "The seawater carbon inventory at the Paleocene–Eocene Thermal Maximum". Proceedings of the National Academy of Sciences of the United States of America. 117 (39): 24088–24095\. Bibcode:2020PNAS..11724088H. doi:10.1073/pnas.2003197117. PMC 7533689. PMID 32929018.
21. ^ a b c d McInherney, F.A.; Wing, S. (2011). "A perturbation of carbon cycle, climate, and biosphere with implications for the future". Annual Review of Earth and Planetary Sciences. 39: 489–516\. Bibcode:2011AREPS..39..489M. doi:10.1146/annurev-earth-040610-133431. Archived from the original on 2016-09-14. Retrieved 2016-02-03.
22. ^ Westerhold, T.; Röhl, U.; Raffi, I.; Fornaciari, E.; Monechi, S.; Reale, V.; Bowles, J.; Evans, H. F. (2008). "Astronomical calibration of the Paleocene time" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 257 (4): 377–403\. Bibcode:2008PPP...257..377W. doi:10.1016/j.palaeo.2007.09.016. Archived (PDF) from the original on 2017-08-09. Retrieved 2019-07-06.
23. ^ Bowen, Gabriel J.; Maibauer, Bianca J.; Kraus, Mary J.; Röhl, Ursula; Westerhold, Thomas; Steimke, Amy; Gingerich, Philip D.; Wing, Scott L.; Clyde, William C. (2015). "Two massive, rapid releases of carbon during the onset of the Palaeocene–Eocene thermal maximum". Nature. 8 (1): 44–47\. Bibcode:2015NatGe...8...44B. doi:10.1038/ngeo2316.
24. ^ Li, Mingsong; Bralower, Timothy J.; Kump, Lee R.; Self-Trail, Jean M.; Zachos, James C.; Rush, William D.; Robinson, Marci M. (2022-09-24). "Astrochronology of the Paleocene-Eocene Thermal Maximum on the Atlantic Coastal Plain". Nature Communications. 13 (1): 5618. doi:10.1038/s41467-022-33390-x. ISSN 2041-1723. PMC 9509358. PMID 36153313.
25. ^ Gutjahr, Marcus; Ridgwell, Andy; Sexton, Philip F.; Anagnostou, Eleni; Pearson, Paul N.; Pälike, Heiko; Norris, Richard D.; Thomas, Ellen; Foster, Gavin L. (August 2017). "Very large release of mostly volcanic carbon during the Palaeocene–Eocene Thermal Maximum". Nature. 548 (7669): 573–577\. Bibcode:2017Natur.548..573G. doi:10.1038/nature23646. ISSN 1476-4687. PMC 5582631. PMID 28858305.
26. ^ Jones, S.M.; Hoggett, M.; Greene, S.E.; Jones, T.D. (2019). "Large Igneous Province thermogenic greenhouse gas flux could have initiated Paleocene-Eocene Thermal Maximum climate change". Nature Communications. 10 (1): 5547. Bibcode:2019NatCo..10.5547J. doi:10.1038/s41467-019-12957-1. PMC 6895149. PMID 31804460.
27. ^ Kennett, J.P.; Stott, L.D. (1991). "Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Paleocene" (PDF). Nature. 353 (6341): 225–229\. Bibcode:1991Natur.353..225K. doi:10.1038/353225a0. S2CID 35071922. Archived from the original (PDF) on 2016-03-03. Retrieved 2020-01-08.
28. ^ Koch, P.L.; Zachos, J.C.; Gingerich, P.D. (1992). "Correlation between isotope records in marine and continental carbon reservoirs near the Palaeocene/Eocene boundary". Nature. 358 (6384): 319–322\. Bibcode:1992Natur.358..319K. doi:10.1038/358319a0. hdl:2027.42/62634. S2CID 4268991.
29. ^ Van der Meulen, Bas; Gingerich, Philip D.; Lourens, Lucas J.; Meijer, Niels; Van Broekhuizen, Sjors; Van Ginneken, Sverre; Abels, Hemmo A. (15 March 2020). "Carbon isotope and mammal recovery from extreme greenhouse warming at the Paleocene–Eocene boundary in astronomically-calibrated fluvial strata, Bighorn Basin, Wyoming, USA". Earth and Planetary Science Letters. 534: 116044. Bibcode:2020E&PSL.53416044V. doi:10.1016/j.epsl.2019.116044. S2CID 212852180.
30. ^ a b Thomas, D.J.; Zachos, J.C.; Bralower, T.J.; Thomas, E.; Bohaty, S. (2002). "Warming the fuel for the fire: Evidence for the thermal dissociation of methane hydrate during the Paleocene-Eocene thermal maximum". Geology. 30 (12): 1067–1070\. Bibcode:2002Geo....30.1067T. doi:10.1130/0091-7613(2002)030<1067:WTFFTF>2.0.CO;2. Archived from the original on 2019-01-08. Retrieved 2024-10-29.
31. ^ Sluijs, A.; Brinkhuis, H.; Schouten, S.; Bohaty, S.M.; John, C.M.; Zachos, J.C.; Reichart, G.J.; Sinninghe Damste, J.S.; Crouch, E.M.; Dickens, G.R. (2007). "Environmental precursors to rapid light carbon injection at the Palaeocene/Eocene boundary". Nature. 450 (7173): 1218–21\. Bibcode:2007Natur.450.1218S. doi:10.1038/nature06400. hdl:1874/31621. PMID 18097406. S2CID 4359625.
32. ^ Tripati, A.; Elderfield, H. (2005). "Deep-Sea Temperature and Circulation Changes at the Paleocene-Eocene Thermal Maximum". Science. 308 (5730): 1894–1898\. Bibcode:2005Sci...308.1894T. doi:10.1126/science.1109202. PMID 15976299. S2CID 38935414.
33. ^ Kelly, D. Clay (28 December 2002). "Response of Antarctic (ODP Site 690) planktonic foraminifera to the Paleocene–Eocene thermal maximum: Faunal evidence for ocean/climate change". Paleoceanography and Paleoclimatology. 17 (4): 23-1 – 23-13. Bibcode:2002PalOc..17.1071K. doi:10.1029/2002PA000761.
34. ^ Zachos, James C; Bohaty, Steven M; John, Cedric M; McCarren, Heather; Kelly, Daniel C; Nielsen, Tina (15 July 2007). "The Palaeocene–Eocene carbon isotope excursion: constraints from individual shell planktonic foraminifer records". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 365 (1856): 1829–1842\. Bibcode:2007RSPTA.365.1829Z. doi:10.1098/rsta.2007.2045. ISSN 1364-503X. PMID 17513259. S2CID 3742682.
35. ^ a b Higgins, John A.; Schrag, Daniel P. (30 May 2006). "Beyond methane: Towards a theory for the Paleocene–Eocene Thermal Maximum". Earth and Planetary Science Letters. 245 (3–4): 523–537\. Bibcode:2006E&PSL.245..523H. doi:10.1016/j.epsl.2006.03.009.3–4&rft.pages=523-537&rft.date=2006-05-30&rft_id=info:doi/10.1016/j.epsl.2006.03.009&rft_id=info:bibcode/2006E&PSL.245..523H;&rft.aulast=Higgins&rft.aufirst=John+A.&rft.au=Schrag,+Daniel+P.&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
36. ^ a b Gu, Guangsheng; Dickens, G.R.; Bhatnagar, G.; Colwell, F.S.; Hirasaki, G.J.; Chapman, W.G. (2011). "Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures". Nature Geoscience. 4 (12): 848–851\. Bibcode:2011NatGe...4..848G. doi:10.1038/ngeo1301.
37. ^ Fox-Kemper, B.; Hewitt, H.T.; Xiao, C.; Aðalgeirsdóttir, G.; Drijfhout, S.S.; Edwards, T.L.; Golledge, N.R.; Hemer, M.; Kopp, R.E.; Krinner, G.; Mix, A. (2021). "Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks". In Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S.L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (PDF) (Report). Cambridge University Press, Cambridge, UK and New York, NY, USA. p. 80\. doi:10.1017/9781009157896.007.
38. ^ Buffett, Bruce; Archer, David (15 November 2004). "Global inventory of methane clathrate: sensitivity to changes in the deep ocean". Earth and Planetary Science Letters. 227 (3): 185–199\. Bibcode:2004E&PSL.227..185B. doi:10.1016/j.epsl.2004.09.005. ISSN 0012-821X.
39. ^ Pagani, Mark; Caldeira, K.; Archer, D.; Zachos, J.C. (8 December 2006). "An Ancient Carbon Mystery". Science. 314 (5805): 1556–7\. doi:10.1126/science.1136110. PMID 17158314. S2CID 128375931.
40. ^ Gehler, Alexander; Gingerich, Philip D.; Pack, Andreas (2015). "Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite". Proceedings of the National Academy of Sciences of the United States of America. 113 (8): 7739–7744\. Bibcode:2016PNAS..113.7739G. doi:10.1073/pnas.1518116113. PMC 4948332. PMID 27354522.
41. ^ Frieling, J.; Peterse, F.; Lunt, D. J.; Bohaty, S. M.; Sinninghe Damsté, J. S.; Reichart, G. -J.; Sluijs, A. (18 March 2019). "Widespread Warming Before and Elevated Barium Burial During the Paleocene-Eocene Thermal Maximum: Evidence for Methane Hydrate Release?". Paleoceanography and Paleoclimatology. 34 (4): 546–566\. Bibcode:2019PaPa...34..546F. doi:10.1029/2018PA003425. PMC 6582550. PMID 31245790.
42. ^ Kender, Sev; Bogus, Kara; Pedersen, Gunver K.; Dybkjær, Karen; Mather, Tamsin A.; Mariani, Erica; Ridgwell, Andy; Riding, James B.; Wagner, Thomas; Hesselbo, Stephen P.; Leng, Melanie J. (31 August 2021). "Paleocene/Eocene carbon feedbacks triggered by volcanic activity". Nature Communications. 12 (1): 5186. Bibcode:2021NatCo..12.5186K. doi:10.1038/s41467-021-25536-0. hdl:10871/126942. ISSN 2041-1723. PMC 8408262. PMID 34465785.
43. ^ Babila, Tali L.; Penman, Donald E.; Standish, Christopher D.; Doubrawa, Monika; Bralower, Timothy J.; Robinson, Marci M.; Self-Trail, Jean M.; Speijer, Robert P.; Stassen, Peter; Foster, Gavin L.; Zachos, James C. (16 March 2022). "Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum". Science Advances. 8 (11). eabg1025. Bibcode:2022SciA....8G1025B. doi:10.1126/sciadv.abg1025. hdl:20.500.12942/694229. PMC 8926327. PMID 35294237. S2CID 247498325.
44. ^ Katz, M.E.; Cramer, B.S.; Mountain, G.S.; Katz, S.; Miller, K.G. (2001). "Uncorking the bottle: What triggered the Paleocene/Eocene thermal maximum methane release". Paleoceanography and Paleoclimatology. 16 (6): 667. Bibcode:2001PalOc..16..549K. CiteSeerX 10.1.1.173.2201. doi:10.1029/2000PA000615.
45. ^ MacDonald, Gordon J. (1990). "Role of methane clathrates in past and future climates". Climatic Change. 16 (3): 247–281\. Bibcode:1990ClCh...16..247M. doi:10.1007/BF00144504. S2CID 153361540.
46. ^ Rohde RA, Muller, RA (2005). "Cycles in fossil diversity". Nature. 434 (7030): 209–210\. Bibcode:2005Natur.434..208R. doi:10.1038/nature03339. PMID 15758998. S2CID 32520208. Retrieved 14 January 2023.
47. ^ McLoughlin, Steven (8 January 2021). "Age and Paleoenvironmental Significance of the Frazer Beach Member – A New Lithostratigraphic Unit Overlying the End-Permian Extinction Horizon in the Sydney Basin, Australia". Frontiers in Earth Science. 8 (600976): 605. Bibcode:2021FrEaS...8..605M. doi:10.3389/feart.2020.600976.
48. ^ a b Beauchamp, Benoit; Grasby, Stephen E. (15 September 2012). "Permian lysocline shoaling and ocean acidification along NW Pangea led to carbonate eradication and chert expansion". Palaeogeography, Palaeoclimatology, Palaeoecology. 350–352: 73–90\. Bibcode:2012PPP...350...73B. doi:10.1016/j.palaeo.2012.06.014. Retrieved 2024-03-26.
49. ^ Jouault, Corentin; Nel, André; Perrichot, Vincent; Legendre, Frédéric; Condamine, Fabien L. (6 December 2011). "Multiple drivers and lineage-specific insect extinctions during the Permo-Triassic". Nature Communications. 13 (1): 7512. doi:10.1038/s41467-022-35284-4. PMC 9726944. PMID 36473862.
50. ^ Delfini, Massimo; Kustatscher, Evelyn; Lavezzi, Fabrizio; Bernardi, Massimo (29 July 2021). "The End-Permian Mass Extinction: Nature's Revolution". In Martinetto, Edoardo; Tschopp, Emanuel; Gastaldo, Robert A. (eds.). Nature through Time. Springer Textbooks in Earth Sciences, Geography and Environment. Springer Cham. pp. 253–267\. doi:10.1007/978-3-030-35058-1_10. ISBN 978-3-030-35060-4. S2CID 226405085.
51. ^ ""Great Dying" lasted 200,000 years". National Geographic. 23 November 2011. Archived from the original on November 24, 2011. Retrieved 1 April 2014.
52. ^ St. Fleur, Nicholas (16 February 2017). "After Earth's worst mass extinction, life rebounded rapidly, fossils suggest". The New York Times. Retrieved 17 February 2017.
53. ^ Algeo, Thomas J. (5 February 2012). "The P–T Extinction was a Slow Death". Astrobiology Magazine. Archived from the original on 2021-03-08.
54. ^ Jurikova, Hana; Gutjahr, Marcus; Wallmann, Klaus; Flögel, Sascha; Liebetrau, Volker; Posenato, Renato; et al. (November 2020). "Permian–Triassic mass extinction pulses driven by major marine carbon cycle perturbations". Nature Geoscience. 13 (11): 745–750\. Bibcode:2020NatGe..13..745J. doi:10.1038/s41561-020-00646-4. hdl:11573/1707839. ISSN 1752-0908. S2CID 224783993. Retrieved 8 November 2020.
55. ^ Erwin, D.H. (1990). "The End-Permian Mass Extinction". Annual Review of Ecology, Evolution, and Systematics. 21: 69–91\. doi:10.1146/annurev.es.21.110190.000441.
56. ^ Chen, Yanlong; Richoz, Sylvain; Krystyn, Leopold; Zhang, Zhifei (August 2019). "Quantitative stratigraphic correlation of Tethyan conodonts across the Smithian-Spathian (Early Triassic) extinction event". Earth-Science Reviews. 195: 37–51\. Bibcode:2019ESRv..195...37C. doi:10.1016/j.earscirev.2019.03.004. S2CID 135139479. Retrieved 28 October 2022.
57. ^ a b Stanley, Steven M. (18 October 2016). "Estimates of the magnitudes of major marine mass extinctions in earth history". Proceedings of the National Academy of Sciences of the United States of America. 113 (42): E6325 – E6334. Bibcode:2016PNAS..113E6325S. doi:10.1073/pnas.1613094113. ISSN 0027-8424. PMC 5081622. PMID 27698119.
58. ^ Benton, M.J. (2005). When Life Nearly Died: The greatest mass extinction of all time. London: Thames & Hudson. ISBN 978-0-500-28573-2.
59. ^ Bergstrom, Carl T.; Dugatkin, Lee Alan (2012). Evolution. Norton. p. 515\. ISBN 978-0-393-92592-0.
60. ^ a b Sahney, S.; Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time". Proceedings of the Royal Society B. 275 (1636): 759–765\. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.
61. ^ Labandeira, Conrad (1 January 2005), "The fossil record of insect extinction: New approaches and future directions", American Entomologist, 51: 14–29, doi:10.1093/ae/51.1.14
62. ^ Marshall, Charles R. (5 January 2023). "Forty years later: The status of the "Big Five" mass extinctions". Cambridge Prisms: Extinction. 1: 1–13\. doi:10.1017/ext.2022.4. PMC 11895713. S2CID 255710815.
63. ^ Jin, Y. G.; Wang, Y.; Wang, W.; Shang, Q. H.; Cao, C. Q.; Erwin, D. H. (21 July 2000). "Pattern of marine mass extinction near the Permian–Triassic boundary in south China". Science. 289 (5478): 432–436\. Bibcode:2000Sci...289..432J. doi:10.1126/science.289.5478.432. PMID 10903200. Retrieved 5 March 2023.
64. ^ Burgess, Seth D.; Bowring, Samuel A. (1 August 2015). "High-precision geochronology confirms voluminous magmatism before, during, and after Earth's most severe extinction". Science Advances. 1 (7): e1500470. Bibcode:2015SciA....1E0470B. doi:10.1126/sciadv.1500470. ISSN 2375-2548. PMC 4643808. PMID 26601239.
65. ^ Dal Corso, Jacopo; Song, Haijun; Callegaro, Sara; Chu, Daoliang; Sun, Yadong; Hilton, Jason; et al. (22 February 2022). "Environmental crises at the Permian–Triassic mass extinction". Nature Reviews Earth & Environment. 3 (3): 197–214\. Bibcode:2022NRvEE...3..197D. doi:10.1038/s43017-021-00259-4. hdl:10852/100010. S2CID 247013868. Retrieved 20 December 2022. "overwhelming data support that the [Permian-Triassic mass extinction] was triggered by the eruption of the [Siberian Traps Large Igneous Province]."
66. ^ Hulse, D; Lau, K.V.; Sebastiaan, J.V.; Arndt, S; Meyer, K.M.; Ridgwell, A (28 Oct 2021). "End-Permian marine extinction due to temperature-driven nutrient recycling and euxinia". Nat Geosci. 14 (11): 862–867\. Bibcode:2021NatGe..14..862H. doi:10.1038/s41561-021-00829-7. S2CID 240076553.
67. ^ Cui, Ying; Kump, Lee R. (October 2015). "Global warming and the end-Permian extinction event: Proxy and modeling perspectives". Earth-Science Reviews. 149: 5–22\. Bibcode:2015ESRv..149....5C. doi:10.1016/j.earscirev.2014.04.007.
68. ^ a b c Wu, Yuyang; Chu, Daoliang; Tong, Jinnan; Song, Haijun; Dal Corso, Jacopo; Wignall, Paul Barry; Song, Huyue; Du, Yong; Cui, Ying (9 April 2021). "Six-fold increase of atmospheric pCO2 during the Permian–Triassic mass extinction". Nature Communications. 12 (1): 2137. Bibcode:2021NatCo..12.2137W. doi:10.1038/s41467-021-22298-7. PMC 8035180. PMID 33837195. S2CID 233200774. Retrieved 2024-03-26.2+during+the+Permian–Triassic+mass+extinction&rft.volume=12&rft.issue=1&rft.pages=2137&rft.date=2021-04-09&rft_id=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8035180#id-name=PMC&rft_id=https://api.semanticscholar.org/CorpusID:233200774#id-name=S2CID&rft_id=info:bibcode/2021NatCo..12.2137W&rft_id=info:pmid/33837195&rft_id=info:doi/10.1038/s41467-021-22298-7&rft.aulast=Wu&rft.aufirst=Yuyang&rft.au=Chu,+Daoliang&rft.au=Tong,+Jinnan&rft.au=Song,+Haijun&rft.au=Dal+Corso,+Jacopo&rft.au=Wignall,+Paul+Barry&rft.au=Song,+Huyue&rft.au=Du,+Yong&rft.au=Cui,+Ying&rft_id=https://www.researchgate.net/publication/350759904&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
69. ^ Frank, T. D.; Fielding, Christopher R.; Winguth, A. M. E.; Savatic, K.; Tevyaw, A.; Winguth, C.; McLoughlin, Stephen; Vajda, Vivi; Mays, C.; Nicoll, R.; Bocking, M.; Crowley, J. L. (19 May 2021). "Pace, magnitude, and nature of terrestrial climate change through the end-Permian extinction in southeastern Gondwana". Geology. 49 (9): 1089–1095\. Bibcode:2021Geo....49.1089F. doi:10.1130/G48795.1. S2CID 236381390. Retrieved 2024-03-26.
70. ^ Joachimski, Michael M.; Lai, Xulong; Shen, Shuzhong; Jiang, Haishui; Luo, Genming; Chen, Bo; Chen, Jun; Sun, Yadong (1 March 2012). "Climate warming in the latest Permian and the Permian–Triassic mass extinction". Geology. 40 (3): 195–198\. Bibcode:2012Geo....40..195J. doi:10.1130/G32707.1. Retrieved 2024-03-26.
71. ^ Clarkson, M.; Kasemann, S.; Wood, R.; Lenton, T.; Daines, S.; Richoz, S.; et al. (2015-04-10). "Ocean acidification and the Permo-Triassic mass extinction" (PDF). Science. 348 (6231): 229–232\. Bibcode:2015Sci...348..229C. doi:10.1126/science.aaa0193. hdl:10871/20741. PMID 25859043. S2CID 28891777.
72. ^ Payne, J.; Turchyn, A.; Paytan, A.; Depaolo, D.; Lehrmann, D.; Yu, M.; Wei, J. (2010). "Calcium isotope constraints on the end-Permian mass extinction". Proceedings of the National Academy of Sciences of the United States of America. 107 (19): 8543–8548\. Bibcode:2010PNAS..107.8543P. doi:10.1073/pnas.0914065107. PMC 2889361. PMID 20421502.
73. ^ Burgess, S. D.; Muirhead, J. D.; Bowring, S. A. (31 July 2017). "Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction". Nature Communications. 8 (1): 164. Bibcode:2017NatCo...8..164B. doi:10.1038/s41467-017-00083-9. PMC 5537227. PMID 28761160. S2CID 3312150.
74. ^ Darcy E. Ogdena & Norman H. Sleep (2011). "Explosive eruption of coal and basalt and the end-Permian mass extinction". Proceedings of the National Academy of Sciences of the United States of America. 109 (1): 59–62\. Bibcode:2012PNAS..109...59O. doi:10.1073/pnas.1118675109. PMC 3252959. PMID 22184229.
75. ^ a b c Berner, R.A. (2002). "Examination of hypotheses for the Permo-Triassic boundary extinction by carbon cycle modeling". Proceedings of the National Academy of Sciences of the United States of America. 99 (7): 4172–4177\. Bibcode:2002PNAS...99.4172B. doi:10.1073/pnas.032095199. PMC 123621. PMID 11917102.
76. ^ Kaiho, Kunio; Aftabuzzaman, Md; Jones, David S.; Tian, Li (4 November 2020). "Pulsed volcanic combustion events coincident with the end-Permian terrestrial disturbance and the following global crisis". Geology. 49 (3): 289–293\. doi:10.1130/G48022.1. ISSN 0091-7613. Available under CC BY 4.0.
77. ^ Rothman, D.H.; Fournier, G.P.; French, K.L.; Alm, E.J.; Boyle, E.A.; Cao, C.; Summons, R.E. (31 March 2014). "Methanogenic burst in the end-Permian carbon cycle". Proceedings of the National Academy of Sciences of the United States of America. 111 (15): 5462–5467\. Bibcode:2014PNAS..111.5462R. doi:10.1073/pnas.1318106111. PMC 3992638. PMID 24706773. – Lay summary: Chandler, David L. (March 31, 2014). "Ancient whodunit may be solved: Methane-producing microbes did it!". Science Daily.
78. ^ Saitoh, Masafumi; Isozaki, Yukio (5 February 2021). "Carbon Isotope Chemostratigraphy Across the Permian-Triassic Boundary at Chaotian, China: Implications for the Global Methane Cycle in the Aftermath of the Extinction". Frontiers in Earth Science. 8: 665. Bibcode:2021FrEaS...8..665S. doi:10.3389/feart.2020.596178.
79. ^ Yadong Sun; Alexander Farnsworth; Michael M. Joachimski; Paul Barry Wignall; Leopold Krystyn; David P. G. Bond; Domenico C. G. Ravidà; Paul J. Valdes (September 12, 2024). "Mega El Niño instigated the end-Permian mass extinction". Science. 385 (6714): 1189–1195\. doi:10.1126/science.ado2030. PMID 39265011.
80. ^ Tohver, Eric; Lana, Cris; Cawood, P.A.; Fletcher, I.R.; Jourdan, F.; Sherlock, S.; et al. (1 June 2012). "Geochronological constraints on the age of a Permo–Triassic impact event: U–Pb and 40Ar / 39Ar results for the 40 km Araguainha structure of central Brazil". Geochimica et Cosmochimica Acta. 86: 214–227\. Bibcode:2012GeCoA..86..214T. doi:10.1016/j.gca.2012.03.005.
81. ^ Tohver, Eric; Cawood, P. A.; Riccomini, Claudio; Lana, Cris; Trindade, R. I. F. (1 October 2013). "Shaking a methane fizz: Seismicity from the Araguainha impact event and the Permian–Triassic global carbon isotope record". Palaeogeography, Palaeoclimatology, Palaeoecology. 387: 66–75\. Bibcode:2013PPP...387...66T. doi:10.1016/j.palaeo.2013.07.010. Retrieved 2024-03-26.
82. ^ Tohver, Eric; Schmieder, Martin; Lana, Cris; Mendes, Pedro S. T.; Jourdan, Fred; Warren, Lucas; Riccomini, Claudio (2 January 2018). "End-Permian impactogenic earthquake and tsunami deposits in the intracratonic Paraná Basin of Brazil". Geological Society of America Bulletin. 130 (7–8): 1099–1120\. Bibcode:2018GSAB..130.1099T. doi:10.1130/B31626.1. Retrieved 2024-03-26.7–8&rft.pages=1099-1120&rft.date=2018-01-02&rft_id=info:doi/10.1130/B31626.1&rft_id=info:bibcode/2018GSAB..130.1099T&rft.aulast=Tohver&rft.aufirst=Eric&rft.au=Schmieder,+Martin&rft.au=Lana,+Cris&rft.au=Mendes,+Pedro+S.+T.&rft.au=Jourdan,+Fred&rft.au=Warren,+Lucas&rft.au=Riccomini,+Claudio&rft_id=https://pubs.geoscienceworld.org/gsa/gsabulletin/article/130/7-8/1099/525698/End-Permian-impactogenic-earthquake-and-tsunami&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
83. ^ Liu, Feng; Peng, Huiping; Marshall, John E. A.; Lomax, Barry H.; Bomfleur, Benjamin; Kent, Matthew S.; Fraser, Wesley T.; Jardine, Phillip E. (6 January 2023). "Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction". Science Advances. 9 (1): eabo6102. Bibcode:2023SciA....9O6102L. doi:10.1126/sciadv.abo6102. PMC 9821938. PMID 36608140.
84. ^ Benca, Jeffrey P.; Duijnstee, Ivo A. P.; Looy, Cindy V. (7 February 2018). "UV-B–induced forest sterility: Implications of ozone shield failure in Earth's largest extinction". Science Advances. 4 (2): e1700618. Bibcode:2018SciA....4..618B. doi:10.1126/sciadv.1700618. PMC 5810612. PMID 29441357.
85. ^ Visscher, Henk; Looy, Cindy V.; Collinson, Margaret E.; Brinkhuis, Henk; Cittert, Johanna H.A. van Konijnenburg; Kürschner, Wolfram M.; Sephton, Mark A. (31 August 2004). "Environmental mutagenesis during the end-Permian ecological crisis". Proceedings of the National Academy of Sciences of the United States of America. 101 (35): 12952–12956\. Bibcode:2004PNAS..10112952V. doi:10.1073/pnas.0404472101. ISSN 0027-8424. PMC 516500. PMID 15282373.
86. ^ Twitchett RJ, Looy CV, Morante R, Visscher H, Wignall PB (2001). "Rapid and synchronous collapse of marine and terrestrial ecosystems during the end-Permian biotic crisis". Geology. 29 (4): 351–354\. Bibcode:2001Geo....29..351T. doi:10.1130/0091-7613(2001)029<0351:RASCOM>2.0.CO;2. ISSN 0091-7613.
87. ^ Palfy J, Demeny A, Haas J, Htenyi M, Orchard MJ, Veto I (2001). "Carbon isotope anomaly at the Triassic–Jurassic boundary from a marine section in Hungary". Geology. 29 (11): 1047–1050\. Bibcode:2001Geo....29.1047P. doi:10.1130/0091-7613(2001)029<1047:CIAAOG>2.0.CO;2. ISSN 0091-7613.
88. ^ a b c d Payne, J.L.; Lehrmann, D.J.; Wei, J.; Orchard, M.J.; Schrag, D.P.; Knoll, A.H. (2004). "Large Perturbations of the Carbon Cycle During Recovery from the End-Permian Extinction" (PDF). Science. 305 (5683): 506–9\. Bibcode:2004Sci...305..506P. CiteSeerX 10.1.1.582.9406. doi:10.1126/science.1097023. PMID 15273391. S2CID 35498132.
89. ^ Reichow MK, Saunders AD, White RV, Pringle MS, Al'Muhkhamedov AI, Medvedev AI, Kirda NP (2002). " 40Ar ⁄ 39Ar  dates from the West Siberian Basin: Siberian flood basalt province doubled" (PDF). Science. 296 (5574): 1846–1849\. Bibcode:2002Sci...296.1846R. doi:10.1126/science.1071671. PMID 12052954. S2CID 28964473.+40Ar+⁄+39Ar++dates+from+the+West+Siberian+Basin:+Siberian+flood+basalt+province+doubled&rft.volume=296&rft.issue=5574&rft.pages=1846-1849&rft.date=2002&rft_id=info:doi/10.1126/science.1071671&rft_id=https://api.semanticscholar.org/CorpusID:28964473#id-name=S2CID&rft_id=info:pmid/12052954&rft_id=info:bibcode/2002Sci...296.1846R&rft.aulast=Reichow&rft.aufirst=MK&rft.au=Saunders,+AD&rft.au=White,+RV&rft.au=Pringle,+MS&rft.au=Al'Muhkhamedov,+AI&rft.au=Medvedev,+AI&rft.au=Kirda,+NP&rft_id=http://eprints.gla.ac.uk/468/1/Reichow_.pdf&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
90. ^ Holser WT, Schoenlaub HP, Attrep Jr M, Boeckelmann K, Klein P, Magaritz M, Orth CJ, Fenninger A, Jenny C, Kralik M, Mauritsch H, Pak E, Schramm JF, Stattegger K, Schmoeller R (1989). "A unique geochemical record at the Permian/Triassic boundary". Nature. 337 (6202): 39–44\. Bibcode:1989Natur.337...39H. doi:10.1038/337039a0. S2CID 8035040.
91. ^ Dobruskina, I.A. (1987). "Phytogeography of Eurasia during the early Triassic". Palaeogeography, Palaeoclimatology, Palaeoecology. 58 (1–2): 75–86\. Bibcode:1987PPP....58...75D. doi:10.1016/0031-0182(87)90007-1.1–2&rft.pages=75-86&rft.date=1987&rft_id=info:doi/10.1016/0031-0182(87)90007-1&rft_id=info:bibcode/1987PPP....58...75D&rft.au=Dobruskina,+I.A.&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
92. ^ Ryskin, Gregory (September 2003). "Methane-driven oceanic eruptions and mass extinctions". Geology. 31 (9): 741–744\. Bibcode:2003Geo....31..741R. doi:10.1130/G19518.1.
93. ^ Krull, Evelyn S.; Retallack, Gregory J. (1 September 2000). "13C depth profiles from paleosols across the Permian–Triassic boundary: Evidence for methane release". Geological Society of America Bulletin. 112 (9): 1459–1472\. Bibcode:2000GSAB..112.1459K. doi:10.1130/0016-7606(2000)112<1459:CDPFPA>2.0.CO;2. ISSN 0016-7606. Retrieved 3 July 2023.
94. ^ a b Erwin, D.H. (1993). The great Paleozoic crisis; Life and death in the Permian. Columbia University Press. ISBN 978-0-231-07467-4.
95. ^ a b Dickens GR, O'Neil JR, Rea DK, Owen RM (1995). "Dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the Paleocene". Paleoceanography and Paleoclimatology. 10 (6): 965–971\. Bibcode:1995PalOc..10..965D. doi:10.1029/95PA02087.
96. ^ White, R. V. (2002). "Earth's biggest 'whodunnit': Unravelling the clues in the case of the end-Permian mass extinction" (PDF). Philosophical Transactions of the Royal Society of London. 360 (1801): 2963–2985\. Bibcode:2002RSPTA.360.2963W. doi:10.1098/rsta.2002.1097. PMID 12626276. S2CID 18078072. Archived from the original (PDF) on 2020-11-11. Retrieved 2008-01-12.
97. ^ Schrag DP, Berner RA, Hoffman PF, Halverson GP (2002). "On the initiation of a snowball Earth". Geochemistry, Geophysics, Geosystems. 3 (6): 1–21\. Bibcode:2002GGG.....3.1036S. doi:10.1029/2001GC000219. Preliminary abstract at Schrag, D.P. (June 2001). "On the initiation of a snowball Earth". Geological Society of America. Archived from the original on 2018-04-25. Retrieved 2008-04-20.
98. ^ Benton, Michael James; Twitchett, R.J. (2003). "How to kill (almost) all life: The end-Permian extinction event". Trends in Ecology & Evolution. 18 (7): 358–365\. doi:10.1016/S0169-5347(03)00093-4.
99. ^ Cui, Ying; Li, Mingsong; van Soelen, Elsbeth E.; Peterse, Francien; M. Kürschner, Wolfram (7 September 2021). "Massive and rapid predominantly volcanic CO2 emission during the end-Permian mass extinction". Proceedings of the National Academy of Sciences of the United States of America. 118 (37): e2014701118. Bibcode:2021PNAS..11814701C. doi:10.1073/pnas.2014701118. PMC 8449420. PMID 34493684.2+emission+during+the+end-Permian+mass+extinction&rft.volume=118&rft.issue=37&rft.pages=e2014701118&rft.date=2021-09-07&rft_id=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8449420#id-name=PMC&rft_id=info:pmid/34493684&rft_id=info:doi/10.1073/pnas.2014701118&rft_id=info:bibcode/2021PNAS..11814701C&rft.aulast=Cui&rft.aufirst=Ying&rft.au=Li,+Mingsong&rft.au=van+Soelen,+Elsbeth+E.&rft.au=Peterse,+Francien&rft.au=M.+Kürschner,+Wolfram&rft_id=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8449420&rfr_id=info:sid/en.wikipedia.org:Clathrate+gun+hypothesis" class="Z3988">
100. ^ Shen, Shu-Zhong; Cao, Chang-Qun; Henderson, Charles M.; Wang, Xiang-Dong; Shi, Guang R.; Wang, Yue; Wang, Wei (January 2006). "End-Permian mass extinction pattern in the northern peri-Gondwanan region". Palaeoworld. 15 (1): 3–30\. doi:10.1016/j.palwor.2006.03.005. Retrieved 26 May 2023.
101. ^ Majorowicz, J.; Grasby, S. E.; Safanda, J.; Beauchamp, B. (1 May 2014). "Gas hydrate contribution to Late Permian global warming". Earth and Planetary Science Letters. 393: 243–253\. Bibcode:2014E&PSL.393..243M. doi:10.1016/j.epsl.2014.03.003. ISSN 0012-821X. Retrieved 12 January 2024 - via Elsevier Science Direct.
102. ^ Archer, D.; Buffett, B. (2005). "Time-dependent response of the global ocean clathrate reservoir to climatic and anthropogenic forcing" (PDF). Geochemistry, Geophysics, Geosystems. 6 (3): Q03002. Bibcode:2005GGG.....6.3002A. doi:10.1029/2004GC000854.
103. ^ a b Archer, D. (2007). "Methane hydrate stability and anthropogenic climate change" (PDF). Biogeosciences. 4 (4): 521–544\. Bibcode:2007BGeo....4..521A. doi:10.5194/bg-4-521-2007. See also blog summary Archived 2007-04-15 at the Wayback Machine.
104. ^ Joung, DongJoo; Ruppel, Carolyn; Southon, John; Weber, Thomas S.; Kessler, John D. (17 October 2022). "Negligible atmospheric release of methane from decomposing hydrates in mid-latitude oceans". Nature Geoscience. 15 (11): 885–891\. Bibcode:2022NatGe..15..885J. doi:10.1038/s41561-022-01044-8. S2CID 252976580.
105. ^ "Ancient ocean methane is not an immediate climate change threat". Phys.org. 18 October 2022. Retrieved 6 July 2023.
106. ^ Corbyn, Zoë (December 7, 2012). "Locked greenhouse gas in Arctic sea may be 'climate canary'". Nature. doi:10.1038/nature.2012.11988. S2CID 130678063. Retrieved April 12, 2014.
107. ^ Shakhova, N.; Semiletov, I.; Panteleev, G. (2005). "The distribution of methane on the Siberian Arctic shelves: Implications for the marine methane cycle". Geophysical Research Letters. 32 (9): L09601. Bibcode:2005GeoRL..32.9601S. doi:10.1029/2005GL022751.
108. ^ "Arctic methane outgassing on the E Siberian Shelf part 1 - the background". SkepticalScience. 2012.
109. ^ "Climate-Hydrate Interactions". USGS. January 14, 2013.
110. ^ Shakhova, Natalia; Semiletov, Igor (November 30, 2010). "Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change" (PDF). Retrieved April 12, 2014.
111. ^ a b "Methane bubbling through seafloor creates undersea hills" (Press release). Monterey Bay Aquarium Research Institute. 5 February 2007. Archived from the original on 11 October 2008.
112. ^ Shakhova, N.; Semiletov, I.; Salyuk, A.; Kosmach, D. (2008). "Anomalies of methane in the atmosphere over the East Siberian shelf: Is there any sign of methane leakage from shallow shelf hydrates?" (PDF). Geophysical Research Abstracts. 10: 01526. Archived from the original (PDF) on 2012-12-22. Retrieved 2008-09-25.
113. ^ Mrasek, Volker (17 April 2008). "A Storehouse of Greenhouse Gases Is Opening in Siberia". Spiegel International Online. "The Russian scientists have estimated what might happen when this Siberian permafrost-seal thaws completely and all the stored gas escapes. They believe the methane content of the planet's atmosphere would increase twelvefold."
114. ^ Preuss, Paul (17 September 2008). "IMPACTS: On the Threshold of Abrupt Climate Changes". Lawrence Berkeley National Laboratory.
115. ^ CCSP; et al. (2008). Abrupt Climate Change. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. Clark. Reston VA: U.S. Geological Survey. Archived from the original on 2013-05-04.
116. ^ Atsushi Obata; Kiyotaka Shibata (June 20, 2012). "Damage of Land Biosphere due to Intense Warming by 1000-Fold Rapid Increase in Atmospheric Methane: Estimation with a Climate–Carbon Cycle Model". J. Climate. 25 (24): 8524–8541\. Bibcode:2012JCli...25.8524O. doi:10.1175/JCLI-D-11-00533.1.
117. ^ Sergienko, V. I.; et al. (September 2012). "The Degradation of Submarine Permafrost and the Destruction of Hydrates on the Shelf of East Arctic Seas as a Potential Cause of the 'Methane Catastrophe': Some Results of Integrated Studies in 2011" (PDF). Doklady Earth Sciences. 446 (1): 1132–1137\. Bibcode:2012DokES.446.1132S. doi:10.1134/S1028334X12080144. ISSN 1028-334X. S2CID 129638485.
118. ^ Phrampus, B. J.; Hornbach, M. J. (December 24, 2012). "Recent changes to the Gulf Stream causing widespread gas hydrate destabilization". Nature. 490 (7421): 527–530\. doi:10.1038/nature.2012.11652. PMID 23099408. S2CID 131370518.
119. ^ "Bill McGuire: Modelling suggests with ice cap melt, an increase in volcanic activity". ClimateState.com. 2014.
120. ^ a b Puglini, Matteo; Brovkin, Victor; Regnier, Pierre; Arndt, Sandra (26 June 2020). "Assessing the potential for non-turbulent methane escape from the East Siberian Arctic Shelf". Biogeosciences. 17 (12): 3247–3275\. Bibcode:2020BGeo...17.3247P. doi:10.5194/bg-17-3247-2020. hdl:21.11116/0000-0003-FC9E-0. S2CID 198415071.
121. ^ Shakhova, N.; Semiletov, I.; Salyuk, A.; Kosmach, D.; Bel'cheva, N. (2007). "Methane release on the Arctic East Siberian shelf" (PDF). Geophysical Research Abstracts. 9: 01071.
122. ^ Connor, Steve (September 23, 2008). "Exclusive: The methane time bomb". The Independent. Retrieved 2008-10-03.
123. ^ Connor, Steve (September 25, 2008). "Hundreds of methane 'plumes' discovered". The Independent. Retrieved 2008-10-03.
124. ^ Translation of a blog entry by Örjan Gustafsson, expedition research leader, 2 September 2008
125. ^ Shakhova, Natalia; Semiletov, Igor; Leifer, Ira; Sergienko, Valentin; Salyuk, Anatoly; Kosmach, Denis; Chernykh, Denis; Stubbs, Chris; Nicolsky, Dmitry; Tumskoy, Vladimir; Gustafsson, Örjan (24 November 2013). "Ebullition and storm-induced methane release from the East Siberian Arctic Shelf". Nature. 7 (1): 64–70\. Bibcode:2014NatGe...7...64S. doi:10.1038/ngeo2007.
126. ^ Thornton, Brett F.; Prytherch, John; Andersson, Kristian; Brooks, Ian M.; Salisbury, Dominic; Tjernström, Michael; Crill, Patrick M. (29 January 2020). "Shipborne eddy covariance observations of methane fluxes constrain Arctic sea emissions". Science Advances. 6 (5): eaay7934. Bibcode:2020SciA....6.7934T. doi:10.1126/sciadv.aay7934. PMC 6989137. PMID 32064354.
127. ^ Sparrow, Katy J.; Kessler, John D.; Southon, John R.; Garcia-Tigreros, Fenix; Schreiner, Kathryn M.; Ruppel, Carolyn D.; Miller, John B.; Lehman, Scott J.; Xu, Xiaomei (17 January 2018). "Limited contribution of ancient methane to surface waters of the U.S. Beaufort Sea shelf". Science Advances. 4 (1): eaao4842. Bibcode:2018SciA....4.4842S. doi:10.1126/sciadv.aao4842. PMC 5771695. PMID 29349299.
128. ^ Hong, Wei-Li; Torres, Marta E.; Carroll, JoLynn; Crémière, Antoine; Panieri, Giuliana; Yao, Haoyi; Serov, Pavel (2017). "Seepage from an arctic shallow marine gas hydrate reservoir is insensitive to momentary ocean warming". Nature Communications. 8 (1): 15745. Bibcode:2017NatCo...815745H. doi:10.1038/ncomms15745. ISSN 2041-1723. PMC 5477557. PMID 28589962.
129. ^ CAGE (August 23, 2017). "Study finds hydrate gun hypothesis unlikely". Phys.org.
130. ^ a b Wallmann; et al. (2018). "Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming". Nature Communications. 9 (1): 83. Bibcode:2018NatCo...9...83W. doi:10.1038/s41467-017-02550-9. PMC 5758787. PMID 29311564.
131. ^ Mau, S.; Römer, M.; Torres, M. E.; Bussmann, I.; Pape, T.; Damm, E.; Geprägs, P.; Wintersteller, P.; Hsu, C.-W.; Loher, M.; Bohrmann, G. (23 February 2017). "Widespread methane seepage along the continental margin off Svalbard - from Bjørnøya to Kongsfjorden". Scientific Reports. 7: 42997. Bibcode:2017NatSR...742997M. doi:10.1038/srep42997. PMC 5322355. PMID 28230189. S2CID 23568012.
132. ^ Silyakova, Anna; Jansson, Pär; Serov, Pavel; Ferré, Benedicte; Pavlov, Alexey K.; Hattermann, Tore; Graves, Carolyn A.; Platt, Stephen M.; Lund Myhre, Cathrine; Gründger, Friederike; Niemann, Helge (1 February 2020). "Physical controls of dynamics of methane venting from a shallow seep area west of Svalbard". Continental Shelf Research. 194: 104030. Bibcode:2020CSR...19404030S. doi:10.1016/j.csr.2019.104030. hdl:10037/16975. S2CID 214097236.
133. ^ Pohlman, John W.; Greinert, Jens; Ruppel, Carolyn; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan (1 February 2020). "Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane". Proceedings of the National Academy of Sciences. 114 (21): 5355–5360\. doi:10.1073/pnas.1618926114. PMC 5448205. PMID 28484018.
134. ^ Skarke, A.; Ruppel, C.; Kodis, M.; Brothers, D.; Lobecker, E. (21 July 2014). "Widespread methane leakage from the sea floor on the northern US Atlantic margin". Nature Geoscience. 7 (9): 657–661\. Bibcode:2014NatGe...7..657S. doi:10.1038/ngeo2232.
135. ^ McGrath, Matt (24 August 2014). "Widespread methane leakage from ocean floor off US coast". BBC. Retrieved 24 August 2014.
136. ^ Gas Hydrate Breakdown Unlikely to Cause Massive Greenhouse Gas Release, USGS Gas Hydrates Project, 2017
137. ^ "Like 'champagne bottles being opened': Scientists document an ancient Arctic methane explosion". The Washington Post. June 1, 2017.
138. ^ "SWIPA 2017 - Press Material". Arctic Council. 2017.
139. ^ Moskvitch, Katia (2014). "Mysterious Siberian crater attributed to methane". Nature. doi:10.1038/nature.2014.15649. S2CID 131534214. Archived from the original on 2014-11-19. Retrieved 2014-08-04.
140. ^ Armstrong McKay, David; Abrams, Jesse; Winkelmann, Ricarda; Sakschewski, Boris; Loriani, Sina; Fetzer, Ingo; Cornell, Sarah; Rockström, Johan; Staal, Arie; Lenton, Timothy (9 September 2022). "Exceeding 1.5°C global warming could trigger multiple climate tipping points". Science. 377 (6611): eabn7950. doi:10.1126/science.abn7950. hdl:10871/131584. ISSN 0036-8075. PMID 36074831. S2CID 252161375.
141. ^ Armstrong McKay, David (9 September 2022). "Exceeding 1.5°C global warming could trigger multiple climate tipping points – paper explainer". climatetippingpoints.info. Retrieved 2 October 2022.

## Further reading

[edit]

* Benton, Michael J.; Twitchett, Richard J. (July 2003). "How to kill (almost) all life: the end-Permian extinction event" (PDF). Trends in Ecology and Evolution. 18 (7): 358–365\. doi:10.1016/S0169-5347(03)00093-4. Archived from the original (PDF) on 2007-04-18. Retrieved 2006-11-26., cited by 21 other articles.
* Svensen, Henrik; Planke, Sverre; Malthe-Sørenssen, Anders; Jamtveit, Bjørn; Myklebust, Reidun Rasmussen; Eidem, Torfinn; Rey, Sebastian S. (2004). "Release of methane from a volcanic basin as a mechanism for initial Eocene global warming". Nature. 429 (6991): 542–545\. Bibcode:2004Natur.429..542S. doi:10.1038/nature02566. PMID 15175747. S2CID 4419088.
* Thomas, Deborah J.; Zachos, James C.; Thomas, Ellen; Bohaty, Steven (2002). "Warming the fuel for the fire: Evidence for the thermal dissociation of methane hydrate during the Paleocene-Eocene thermal maximum" (PDF). Geology. 30 (12): 1067–70\. Bibcode:2002Geo....30.1067T. doi:10.1130/0091-7613(2002)030<1067:WTFFTF>2.0.CO;2. ISSN 0091-7613.
* Archer, D.; Buffett, B. (2004). "Temperature sensitivity and time dependence of the global ocean clathrate reservoir". American Geophysical Union, Fall Meeting. Bibcode:2004AGUFMGC51D1069A.

## External links

[edit]

* Kennett, James P. (20 May 2005). "Abstract: Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis". Paul A. Witherspoon Distinguished Seminar Series. Earth Sciences Division, Lawrence Berkeley National Laboratory. Archived from the original on 22 July 2012. Retrieved 17 March 2013.
* Hudson, Geoff (24 May 2009). "The trigger for the clathrate gun". Ockham's Razor. Radio National, Australian Broadcasting Corporation.
* Chakoumakos, Bryan C. (2004). "Preface to the Clathrate Hydrates special issue" (PDF). American Mineralogist. 89: 1153–4.
* Adam, David (14 January 2010). "Arctic permafrost leaking methane at record levels, figures show". Guardian.
* Harris, Richard (26 January 2010). "Methane Causes Vicious Cycle In Global Warming". NPR.org. NPR.
* Methane: A Scientific Journey from Obscurity to Climate Super-Stardom Good Sept. 2004 background report from NASA GISS
* Wakening the Kraken

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