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Evidence: melting permafrost & burning ice

Evidence: melting permafrost & burning ice

(Image: Katie Orlinksy, National Geographic)

Dangerous tipping points: melting permafrost and  burning ice

Summary

  • Permafrost is a combination of soil, sediment, and the remains of dead plants and animals that stay at or below 0°C for at least two years. As thin as <1m and as thick as >1,000m (Fig. 1), deeper layers have been frozen for millions of years.
  • Permafrost covers ~22.79 million km²(~24% of land) of the Northern Hemisphere. Most in the Southern Hemisphere is in Antarctica, with smaller amounts in Patagonia and New Zealand’s Southern Alps. It currently stores ~1,600 billion tonnes of carbon—more than twice what’s in the atmosphere today.

“..melting permafrost is contributing 600 million metric tonnes of net carbon (methane and carbon dioxide) per year into Earth’s atmosphere.”NOAA’s 2019 report card

  •  Permafrost is thawing much faster than expected; not surprising given record breaking summer temperatures up to 45°C in Siberia in  2020 (Fig. 1).
  • Until recently it had been assumed that permafrost would melt slowly enough for the released carbon dioxide and methane to be absorbed by more plants growing further north and longer summers. However, recent research collated by over fifty scientist show that is not the case.
  • Further research shows that decomposition rates of permafrost can accelerate up to fourfold in the presence of plant roots. This effect is not considered in current climate models.
  • Methane ‘clathrates’ look like ice but are flammable (Fig. 5). 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 (USGS) estimates the amount of carbon in clathrates is twice the amount of carbon that exists in all the fossil fuels on Earth.

“Methane’s increase since 2007 was not expected in future greenhouse gas scenarios compliant with the targets of the Paris Agreement, and if the increase continues at the same rates it may become very difficult to meet the Paris goals.” Nisbet et al 2019

Melting permafrost

Video 1: Methane bubbles forming beneath lakes.

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 (Videos 1 & 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).

Video 2: Methane ‘bursts’; at the time of this video in 2013, the average rise in global temperatures was 0.8°C. In 2020 it was an average 1.1°C and climbing. In June 2020, parts of the Russian Arctic reached 45°C (Fig. 1).

“…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

Fig. 1: “Parts of the Russian Arctic have experienced record-breaking high temperatures in recent weeks. This heat map — produced using data from a European Sentinel-3 satellite — shows air temperatures of up to 45°C in some places on 19 June. The heat has been linked to thawing permafrost, widespread wildfires, and swarms of tree-eating moths.” (Image: European Union, Copernicus Sentinel-3)
Fig. 2: Image from the 2021 feature in the journal Nature: ‘How microbes in permafrost could trigger a massive carbon bomb’. Click on the image to read the full story (Image: Nature |Sources: Data from Permafrost CCI; J. OBU et al. Data set at CEDA Archive https://doi.org/ghjkb2 (2020)
Fig. 3: 2019 September issue of National Geographic. Another stunning image from the photo essay by Katie Orlinsky that revels just a very tiny portion of permafrost exposed in the Siberian tundra at the Batagay ‘megaslump’. Click on the image to be taken to the story. Fig. 2 is a photograph at ground level.
Fig. 4: Note the trees at the top are large mature confers. A solitary person is standing a the edge of the cliff just to the right of orange vegetation hanging over the edge. Click on the image to be taken to the story.

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. 5).

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 USGS regard methane clathrates (Fig. 4) as fossil fuel resource; one cubic metre of methane hydrate produces between 163-180 cubic metres of natural gas (so the explosive potential is also high). While they have identified the risks of mining it…

The result might be 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 (Fig. 6). Video 3 explores, 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 (cover image of Video 3; link to the 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 3, 4, 7 & 8).

“Here we are. It’s 2020, and [atmospheric methane] is not only not dropping. It’s not level. In fact, it’s one of the fastest growth rates we’ve seen in the last 20 years.”  Drew Shindell, Duke University

Fig. 5: Methane clathrate or hydrate is, like all fossil fuels, highly flammable. (Image: NASA GISS)

Video 3: Explains the processes that formed methane clathrates, why they are now melting, and the implications.

Fig. 6: Arctic temperature anomalies across the Arctic ocean and coastlines 13 May 2020. Temperatures are in Centigrade. (Image: Computer model simulation (Karsten Haustein)/ Washington Post 14 May 2020) This extreme warming continued into June (Fig. 1).
Fig. 7: Methane eruptions produce craters or ‘pingoes’. These were uncommon until around 2015 (Image: Prof. Vasily Bogoyavlensky / Siberian Times)
Fig. 8: Methane-eruption craters are now appearing across wide stretches of Siberia (Image: Encyclopedia Environment)

References and further reading