Millions of tons of organic carbon and methane under the Arctic Ocean thaw and seep to the surface every year. And climate change could accelerate this release of greenhouse gases, new research suggests.
The carbon bound in organic matter and methane (a carbon atom bound to four hydrogen atoms) is currently trapped in submarine permafrost, which is frozen sediment that was covered by 120 meters of seawater for about 1800 by the end of the Paleolithic Ice Age. up to 1400 years ago, according to the US Geological Survey (USGS). Most undersea permafrost resides on the continental shelf beneath the Arctic Ocean, said study author Sayedeh Sara Sayedi, a doctoral student in the department of plant and natural sciences at Brigham Young University in Salt Lake City.
Because that sediment is in such an inaccessible place, there’s only a tiny bit of patchy data on how much carbon and methane are buried there and how quickly those gases escape into the ocean and the atmosphere above, Sayedi added.
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Some scientists Think of this greenhouse gas reservoir as a ticking time bomb, one that could suddenly spit into the atmosphere and trigger a climate disaster. But Sayedi and her colleagues propose a different scenario: Instead of a sudden release, these gases have been slowly and steadily seeping out of the permafrost for centuries. Man-made climate change could still worsen the situation by accelerating the rate of release, but this acceleration would occur over several centuries, not decades or years.
“Still, the decisions we make today will make a difference in how it will be affected,” Sayedi told Live Science.
In their new study, published Dec. 22 in the journal Environmental research lettersthe team tried to get a comprehensive picture of submarine permafrost using all of the fragmentary data currently available; They also asked 25 permafrost scientists to use their expertise to estimate how much organic carbon is hidden in each specific layer of submarine permafrost. By putting together their perspectives, the team captured a more detailed view of the ecosystem as a whole, and they estimate that permafrost currently contains about 60 billion tons (544 tons) of methane and 560 billion tons (508 tons) of organic carbon. .
Each year, about 140 million tons (128 tons) of carbon dioxide and 5.3 million tons (4.8 tons) of methane from permafrost escape into the atmosphere, they estimate. That’s roughly equivalent to Spain’s carbon footprint, according to a statement. That said, due to the scarcity of data, these emission estimates remain highly uncertain, the authors noted.
The authors also concluded that many of these greenhouse gas emissions were not primarily driven by recent human activity, but began after the last ice age, when the ice sheets were at their greatest. However, human-driven changes could still push up these emissions “over hundreds or thousands of years,” they wrote.
In fact, over the next 300 years, the experts expect that greenhouse gas emissions from submarine permafrost will increase significantly if the carbon emissions from human activity continue as normal. If emissions increase in the 21st century, permafrost would emit four times more greenhouse gases than if emissions started to decline by the end of this year and reach net zero by 2100.
In the business-as-usual scenario, the increase in emissions would increase over the next few centuries, but not enough to create a so-called “methane bomb”.
By overlooking submarine permafrost in climate change models, scientists risk miscalculating the amount of greenhouse gas being emitted into the atmosphere, which could skew where we set our goals for reducing emissions, Sayedi said. Over the next five to 10 years, Sayedi said she hopes additional research on underwater permafrost can help fill in the gaps in our knowledge and provide more certainty about how much carbon is actually there – and how much is coming out. Other factors, such as the size of the sea ice cover, can also affect the amount of gas leaking into the atmosphere, as the ice can serve as a ceiling that traps the gas beneath it, she said.
Originally published on Live Science.