Evidence: melting permafrost & burning ice
- Methane ‘clathrates’ look like ice but are flammable (Fig. 4).
- 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 them is twice the amount of carbon that exists in all the fossil fuels on Earth.
(Image: Katie Orlinksy, National Geographic)
Dangerous tipping points: melting permafrost and burning ice
- 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 the exposed land surface) of the Northern Hemisphere. Most of the permafrost in the Southern Hemisphere is in Antarctica, with smaller amounts in Patagonia and New Zealand’s Southern Alps.
- Until recently it had been assumed that permafrost would melt slowly enough for the released carbon 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.
- Additional research shows that decomposition rates of permafrost can accelerate up to fourfold in the presence of plant roots. The effect of this is not currently considered in climate models.
- Moreover, permafrost is now thawing much faster than expected, especially given the record-breaking summer temperatures up to 45°C in Siberia in June 2020 (Fig. 1).
“..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
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).
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
“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).
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. 2).
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. 5). 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 2, 3, 6 & 7).
“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
References and further reading
- National Snow and Ice Data Centre (NSIDC)
- 2020 (June) Washington Post: Hottest Arctic temperature record probably set with 100-degree reading in Siberia
- 2020 Copernicus Climate Change Services: Investigating an unusually mild winter and spring in Siberia
- 2020: Turetsky et al; Carbon release through abrupt permafrost thaw, Nature Geoscience 13, pp138–143
- 2020: Thomas et al; Tipping elements and amplified polar warming during the Last Interglacial, Quaternary Science Reviews 233 / 106222
- 2020: England et al; Tropical climate responses to projected Arctic and Antarctic sea-ice loss Nature Geoscience 13, 275–281
- 2020 Brendryen et al; Eurasian Ice Sheet collapse was a major source of Meltwater Pulse 1A 14,600 years ago, Nature Geoscience 13, 363–368
- 2020 The Guardian: Antarctic temperature rises above 20C for first time on record
- 2019: Lade et al; Human impacts on planetary boundaries amplified by Earth system interactions, Nature Sustainability 3, pp 119–128
- 2019: Lenton et al; Climate tipping points — too risky to bet against, Nature article (free to access)
- 2019 IPCC: Special Report on the Ocean and Cryosphere in a Changing Climate
- 2020: Scientific American news article: Methane Levels Reach an All-Time High
- 2019: Shakova et al; Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf; Geosciences 9(6), 251
- 2019: Nisbet et al; Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement, Global Biogeochemical Cycles 33/3 pp318-342
- 2019: Chuvilin (ed.) Special Issue “Gas and Gas Hydrate in Permafrost” A special issue of Geosciences (ISSN 2076-3263)
- 2019: Lamarche-Gagnon et al; Greenland melt drives continuous export of methane from the ice-sheet bed, Nature 565, pp73–77
- 2019: NOAA Richter-Menge et al; Arctic Report Card 2019
- 2019: Natali et al; Large loss of CO2 in winter observed across the northern permafrost region Nature Climate Change 9, pp852–857
- 2019: National Geographic: The Arctic Is Heating Up September 2019 special issue
- 2019: The Permafrost Encyclopedia of the Environment
- 2018 IPCC: Summary for Policymakers of IPCC Special Report on Global Warming of 1.5°C approved by governments
- 2018: Carbon Brief Analysis; Why the IPCC 1.5C report expanded the carbon budget
- 2017: Jones; How the World Passed a Carbon Threshold and Why It Matters, Yale Environment 360 – Yale School of Forestry & Environmental Studies
- 2016: Sattler et al; Estimating Permafrost Distribution in the Maritime Southern Alps, New Zealand, Based on Climatic Conditions at Rock Glacier Sites, Frontiers in Earth Science 4/4
- 2015: Solved? How scientists say mystery craters were formed in northern Siberia The Siberian Times
- 2015: United Nations Climate Change: The Paris Agreement
- 2015 Carbon Brief interactive: The Paris Agreement
- 2010: Ditlevsen: Tipping points: Early warning and wishful thinking, Geophysical Research Letters 37/19