Arctic methane emissions



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 (meaning one that amplifies warming), 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.

Large quantities of methane are stored in the Arctic in natural gas deposits and as methane clathrates under sediments on the ocean floors. Clathrates also degrade on warming and release methane directly.

Atmospheric methane concentrations are 8–10% higher in the Arctic than in the Antarctic atmosphere. During cold glacier epochs, this gradient decreases to insignificant levels. Land ecosystems are thought to be the main sources of this asymmetry, although it has been suggested in 2007 that "the role of the Arctic Ocean is significantly underestimated." Soil temperature and moisture levels are important variables in soil methane fluxes in tundra environments.

Mitigation of CO2 emissions by 2050 (ie reaching net zero emissions) is probably not enough to stop the future disappearance of summer Arctic Ocean ice cover. Mitigation of methane emissions is also necessary and this has to be carried out over an even shorter period of time. Mitigation of methane emissions from human activities needs to be carried out within three sectors: oil and gas, waste and agriculture. Using available measures this would amount to global reductions of ca.180 Mt/yr or about 45% of the current (2021) emissions by 2030.

Arctic sea ice decline
A 2015 study concluded that Arctic sea ice decline accelerates methane emissions from the Arctic tundra, with the emissions for 2005-2010 being around 1.7 million tonnes higher than they would have been with the sea ice at 1981–1990 levels. One of the researchers noted, "The expectation is that with further sea ice decline, temperatures in the Arctic will continue to rise, and so will methane emissions from northern wetlands."

Greenland ice sheet
A 2014 study found evidence for methane cycling below the ice sheet of the Russell Glacier, based on subglacial drainage samples which were dominated by Pseudomonadota bacteria. During the study, the most widespread surface melt on record for the past 120 years was observed in Greenland; on 12 July 2012, unfrozen water was present on almost the entire ice sheet surface (98.6%). The findings indicate that methanotrophs could serve as a biological methane sink in the subglacial ecosystem, and the region was, at least during the sample time, a source of atmospheric methane. Scaled dissolved methane flux during the 4 months of the summer melt season for the Russell Glacier catchment area (1200 km2) was estimated at 990 tonnes CH4. Because this catchment area is representative of similar Greenland outlet glaciers, the researchers concluded that the Greenland Ice Sheet may represent a significant global methane source. A study in 2016 concluded that methane clathrates may exist below Greenland's and Antarctica's ice sheets, based on past evidence.

Contributions to climate change
Due to the relatively short lifetime of atmospheric methane (7-12 years compared to 100s of years for CO2 ) its global trends are more complex than those of carbon dioxide. NOAA annual records have been updated since 1984, and they show substantial growth during the 1980s, a slowdown in annual growth during the 1990s, a plateau (including some years of declining atmospheric concentrations) in the early 2000s and another consistent increase beginning in 2007. Since around 2018, there has been consistent annual increases in global levels of methane, with the 2020 increase of 15.06 parts per billion breaking the previous record increase of 14.05 ppb set in 1991, and 2021 setting an even larger increase of 18.34 ppb.

These trends alarm climate scientists, with some suggesting that they represent a climate change feedback increasing natural methane emissions well beyond their preindustrial levels. However, there is currently no evidence connecting the Arctic to this recent acceleration. In fact, a 2021 study indicated that the role of the Arctic was typically overestimated in global methane accounting, while the role of tropical regions was consistently underestimated. The study suggested that tropical wetland methane emissions were the culprit behind the recent growth trend, and this hypothesis was reinforced by a 2022 paper connecting tropical terrestrial emissions to 80% of the global atmospheric methane trends between 2010 and 2019.

Nevertheless, the Arctic's role in global methane trends is considered very likely to increase in the future. There is evidence for increasing methane emissions since 2004 from a Siberian permafrost site into the atmosphere linked to warming.

Reducing methane emissions
More than half of global methane emissions originate from human activities across three main sectors: fossil fuels (35% of human-caused emissions), waste (20%), and agriculture (40%). Within the fossil fuel sector, oil and gas extraction, processing, and distribution contribute 23%, while coal mining accounts for 12% of these emissions. In the waste sector, landfills and wastewater comprise about 20% of global anthropogenic emissions. In agriculture, livestock emissions from manure and enteric fermentation make up roughly 32%, and rice cultivation contributes 8% of global anthropogenic emissions. Mitigation using available measures could reduce these emissions by ca. 180 Mt/yr or about 45% by 2030.

Mitigation of CO2 emissions by 2050 (ie reaching net zero emissions) is probably not enough to stop the future disappearance of summer Arctic Ocean ice cover. Mitigation of methane emissions is also necessary and this has to be carried out over an even shorter period of time.

Flaring methane from oil and gas operations
ARPA-E has funded a research project from 2021-2023 to develop a "smart micro-flare fleet" to burn off methane emissions at remote locations.

A 2012 review article stated that most existing technologies "operate on confined gas streams of 0.1% methane", and were most suitable for areas where methane is emitted in pockets.

If Arctic oil and gas operations use Best Available Technology (BAT) and Best Environmental Practices (BEP) in petroleum gas flaring, this can result in significant methane emissions reductions, according to the Arctic Council.