Millions of tons of organic carbon and methane under the Arctic Ocean thaw and spring to the surface every year. And climate change could accelerate this release greenhouse gases, suggests new research.
The carbon bound in organic matter and methane (a carbon atom bound to four hydrogen atoms) are currently trapped in submarine permafrost, a frozen sediment covered with 120 meters of seawater near the end of the Paleolithic ice age about 1,800 to 1,400 years ago, according to the U.S. Geological Survey (USGS). Most of the submarine permafrost is located in the continental shelf below the Arctic Ocean, said study author Sayedeh Sara Sayedi, a doctoral student in the Department of Plant and Wildlife Sciences at Brigham Young University in Salt Lake City.
Because the sediment is located in such an inaccessible place, there is little part of the data on how much carbon and methane lies buried there and how quickly these gases escape into the ocean and atmosphere above, Sayedi added.
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Some scientists consider this reservoir of greenhouse gases to be a ticking time bomb that could suddenly explode into the atmosphere and cause a climate catastrophe. But Sayedi and her colleagues suggest a different scenario: for centuries, these gases have been slowly and steadily emanating from the permafrost, rather than a sudden release. The human cause climate change it could still aggravate the situation by accelerating the release rate, but that acceleration would happen over several centuries, not decades or years.
“Yet the decisions we make today will make a change in the way it will impact,” Sayedi told Live Science.
In their new study, published December 22 in the journal Letters on environmental research, the team attempted to collect a comprehensive picture of submarine permafrost using all the individual data currently available; they also asked 25 permafrost scientists to use their expertise to estimate how much organic carbon is hidden in each particular layer of submarine permafrost. Compiling their perspectives, the team recorded a more detailed picture of the ecosystem as a whole, and estimated that permafrost currently contains about 60 billion tons (544 metric tons) of methane and 560 billion tons (508 metric tons) of organic carbon.
They estimated that about 140 million tons (128 metric tons) of carbon dioxide and 5.3 million tons (4.8 metric tons) of methane escape from permafrost into the atmosphere each year. That’s roughly the equivalent of Spain’s carbon footprint, according to the statement. However, due to a lack of data, these emission estimates remain very uncertain, the authors noted.
The authors also concluded that, instead of being primarily driven by recent human activities, much of these greenhouse gas emissions began after the Last Ice Maximum, when ice sheets were at their peak. However, human change can still drive these shows “in a few hundred or a thousand years,” they wrote.
In fact, over the next 300 years, experts expect the rate of greenhouse gas emissions from submarine permafrost to increase significantly if carbon emissions from human activities continue as usual. If emissions increase during the 21st century, permafrost will release four times more greenhouse gases than if emissions begin to decline by the end of this year and reach net zero by 2100.
In a normal business scenario, the increase in emissions would increase over the next few centuries, but still not enough to create a so-called “methane bomb”.
By overlooking submarine permafrost in climate change models, scientists run the risk of miscalculating the amount of greenhouse gases emitted into the atmosphere, which could lead to distortions where we have set emissions reduction targets, Sayedi said. Over the next five to 10 years, Sayedi said she hopes further research into submarine permafrost will help fill gaps in our knowledge and provide more certainty about how much carbon is actually down there – and how much is coming out. Other factors, such as the extent of sea ice, can also affect how much gas leaks into the atmosphere, because ice can act as a ceiling that traps gas beneath it, she said.
Originally posted on Live Science.