Image: Katie Orlinksy, National Geographic
Melting permafrost (Northern Hemisphere)
Unlike ice, permafrost doesn’t ‘melt’ once temperatures rise above 0°C. It falls apart and the organic material decomposes, just as frozen meat or vegetables left outside a freezer will decompose if not eaten. If permafrost decomposes in an environment where there’s oxygen, then carbon dioxide is released. If the environment is anaerobic (lacks oxygen), methane, which is 23 times more potent that carbon dioxide as a greehouse gas, is released. This enters the atmosphere either directly or via lakes and ponds (Video 2):
We managed to put a finger on when exactly when continuous permafrost melt starts…this is probably the tipping point, 1.5°C warming. – Dr Anton Vaks, Oxford University
Video 2: This episode of ‘Weathered’ explores the latest (2023) research on the possibilities of abrupt permafrost thaw as well as the much deeper yedoma regions that could be triggered later on.
..ice sheets overlie extensive, biologically active methan-ogenic wetlands and high rates of methane export to the atmosphere can occur via efficient subglacial drainage pathways. Our findings suggest that such environments have been previously underappreciated and should be considered in Earth’s methane budget. – Lamarche-Gagnon et al 2019
The ‘subglacial drainage’ process that’s melting glaciers and ice sheets described in the section on Antarctica, is also awakening microbes in ancient swamps and releasing methane from beneath Greenland. Antarctica is many times larger than Greenland and was once covered in lush forests, so is likely to have very large areas of permafrost.
Several orders of magnitude more methane has been hypothesized to be capped beneath the Antarctic Ice Sheet than beneath Arctic ice-masses. Like we did in Greenland, it’s time to put more robust numbers on the theory. – Lamarche-Gagnon 2019
Burning ice: methane clathrates
Methane clathrates, also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is composed of methane trapped and frozen within a crystal structure of water, forming a solid that looks like ice but is highly flammable (Fig. 6).
Once thought to exist only in the frozen outer parts of the Solar System, it turns out to abundant in permafrost and beneath the ocean floor.
The United States Geological Service estimates regard methane clathrates as a fossil fuel resource; estimating that the amount of carbon in clathrates is twice the amount of carbon that exists in all the fossil fuels on Earth. One cubic metre of methane hydrate produces between 163-180 cubic metres of natural gas (so the explosive potential is also high). Mining it risks:
…gas blowouts, loss of support for pipelines, and sea-floor failure that could lead to underwater landslides and the release of methane from hydrates. – USGS
…the prospect of so much cheap gas is hugely appealing, especially as the Arctic is becoming increasingly accessible as more sea ice melts each year.
‘Tipping points’ are being exceeded in large areas as the Arctic Ocean also experiences record breaking temperatures for extended periods . Videos 3 & 4 explore, amongst other impacts, how methane erupts due to melting permafrost.
In shallow coastal waters and lakes, methane bubbles to the surface and escape directly into the atmosphere (image at the top of this page; see peer-reviewed open access paper by Shakova et al.)
In deep waters, the methane dissolves before reaching the surface. On the land and underwater, these abrupt explosive ‘burbs’ are forming large craters (Figs. 4, 5, 7 & 8).
Video 3: Explains how methane clathrates formed, why they are now melting, and the implications.
Video 4: Explains that large scale melting of clathrates in 2020 after Siberia experienced temperatures up to 45C (Fig. 6).
