AGU - Northern Hermisphere Permafrost Net Carbon Source; Small (For Now) Compared To Major Industrial Economies

Last edited Tue Apr 16, 2024, 08:10 AM - Edit history (1)

The American Geological Union’s magazine EOS has published an article warning that Northern Hemisphere frozen soils (permafrost) emit more carbon and other greenhouse gases than the biome can sink below the surface. Permafrost is permanently frozen soil near the surface to significant depths, with the shallowest deposits at three feet and the deepest deposits at 4,900 feet. The oldest permafrost is estimated to be 700,000 years old.

Permafrost limits the microbial decomposition of soil rich with dead plants and animals that have accumulated for tens of thousands of years by providing a frozen cap that repels greenhouse gases from bubbling to the surface and into the atmosphere. Once the cap unfreezes, water begins to saturate the soil, creating a perfect substrate for microbial activity to release methane or carbon dioxide. With global warming, the process of this part of the carbon cycle has changed. Though emissions from permafrost are currently low, that will change as the soil continues to thaw and rivers and deltas erode, slumping soils and formation of thermokarst lakes and ponds in yet another vicious feedback amplifies climate change impacts across the globe.

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From Saima May Sidik:

The researchers compiled many past estimates of greenhouse gas flux in various sections of the northern permafrost region to reveal how the entire area is responding to climate change. They found that the study area was a net source of CH4 and N2O between 2000 and 2020. Wetlands were some of the largest methane emitters, and lakes contributed substantially as well. Dry tundra was the biggest driver of N2O release, and permafrost bogs were a close second. However, the researchers were unable to say definitively whether the region was a net source or sink of CO2. Terrestrial ecosystems, particularly boreal forests, still take up CO2. But this is offset by fires, abrupt permafrost thaw, and inland waters, which emitted an estimated 12 million metric tons of CO2.

The researchers estimate that the northern permafrost region emitted 38 million metric tons of CH4 and 670,000 metric tons of N2O into the atmosphere between 2000 and 2020. When accounting for lateral fluxes such as erosion, the region was also a source of 144 million metric tons of carbon and 3 million metric tons of nitrogen. That’s very little compared with the emissions of a major industrialized country, but the pace may accelerate as the world warms. (Global Biogeochemical Cycles).

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https://www.dailykos.com/stories/2024/4/15/2235392/-The-Northern-Hemisphere-permafrost-has-transitioned-from-a-carbon-source-to-a-carbon-emitter?pm_campaign=front_page&pm_source=trending&pm_medium=web