Emissions from underground?

Article by Isabel Key and Mina Frost.

Not all greenhouse gas emissions are released directly by human activities [13]; frozen soil, for example, releases greenhouse gases when it melts [1,4]. Frozen soil in and around the Arctic stores large amounts of carbon [1]. This frozen soil is called “permafrost” because it has been permanently frozen for at least 2 years [8]. However, today parts of it are melting that had been frozen for thousands of years [4]!

When permafrost melts, carbon locked up in dead matter is exposed to oxygen, allowing microorganisms (microscopic living things like bacteria [9]) to digest the dead animals and plants in the soil [1,2,3]. In the process, they release methane and carbon dioxide (two important greenhouse gases [10]) into the atmosphere [1]. Swipe for a diagram!

There is great uncertainty as to how much carbon is stored in permafrost, and how fast it could be released [4,5,6]. Permafrost can sometimes melt abruptly: when the ice holding soil together melts, the land can sink and fill with water creating a lake [4]. Land that was covered in forest one year can be covered in lakes the next [4,11]!

Even if humans stopped emitting greenhouse gases today, the methane and carbon dioxide from permafrost is expected to continue being released beyond the end of this century [1] due to temperatures continuing to rise and ice taking time to melt [1,7].

Methane and carbon dioxide are greenhouse gases that warm the atmosphere [12]. It’s expected that release of these gases from permafrost will make climate change happen faster than current predictions [1,4].

References

[1] https://www.nature.com/articles/nature14338 See: Abstract; Main; Permafrost and the global carbon cycle

[2] https://www.nature.com/articles/s41579-018-0066-4 See: Main, paragraph 1

[3] https://www.nature.com/articles/nclimate3328 See: Abstract. Note: changes in surface wetness or wetland, rather than melting of previously frozen soil, can be an important source of carbon emissions

[4] https://www.nature.com/articles/d41586-019-01313-4 See: Paragraph 4; Twice the problem, paragraph 8

[5] https://link.springer.com/article/10.1007/s42452-019-0242-9 Towards determining spatial methane distribution on Arctic permafrost bluffs with an unmanned aerial system, Oberle et al. 2019. Within paper see: Introduction

[6] https://iopscience.iop.org/article/10.1088/1748-9326/aaa138/meta CO2 loss by permafrost thawing implies additional emissions reductions to limit warming to 1.5 or 2 °C, Burke et al. 2018. Within paper see: Abstract

[7] https://archive.ipcc.ch/ipccreports/tar/vol4/011.htm See: Inertia in Climate Systems

[8] https://climatekids.nasa.gov/permafrost/

[9] https://www.merriam-webster.com/dictionary/microorganism

[10] https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions See: Greenhouse gas emissions by gas source

[11] https://www.nature.com/articles/ncomms13043

[12] https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions See: Paragraph 1

[13] https://www.carbonbrief.org/guest-post-understanding-climate-feedbacks

Diagram from:

[14] https://projects.thestar.com/climate-change-canada/nunavut/ See: This photo, taken on Herschel Island in the Yukon, shows an ice wedge that extends about five metres below the active layer

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