Global warming is accelerating the thawing of permafrost – soil that has been at or below the freezing point of water for approximately two or more years. This releases the potent greenhouse gas methane to the atmosphere.
This direct release of methane (the main component in natural gas) occurs when methane-producing bacteria consume organic matter in the rotting soil that has been stored in permafrost over the millennia. Thus, many scientists predict large releases of methane from these sources as a result of global warming.
This is likely what you have already heard about permafrost. Indeed, most of the recent news and interest about permafrost thawing is associated with Arctic and Antarctic regions, even though alpine permafrost does exist in low latitudes as well.
What you have not likely heard about concerns an interesting twist regarding a certain type of organic matter stored in permafrost, which scientists have been talking about for the past decade. It is called yedoma, and is generally defined as organic-rich (about 2% by mass) Pleistocene-age permafrost comprised of 50% to 90% ice, by volume. Yedoma is stored in tens to hundreds of meters of permafrost in the Arctic.
We and others have recently shown that as this permafrost thaws, yedoma is released to the surrounding soils and some gets transported by rivers from land to the Arctic Ocean.
While most scientists would have predicted that this very old organic matter would not be very digestible to modern-day organisms, such as bacteria, it turns out that it is extremely “fresh” in its composition and consequently highly bio-available to microbes.
This, it turns out, has big implications for permafrost and global warming because this process produces another greenhouse gas: carbon dioxide.
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