submarine permafrost still wakes up after 12,000 years

In the far north, the swollen Arctic Ocean has flooded large areas of coastal and steppe tundra ecosystems. Although the ocean water was only a few degrees above freezing, it began to thaw the permafrost beneath it, exposing billions of tons of organic matter to microbial decomposition. Decomposing organic matter began to produce CO₂ and CH₄, two of the most important greenhouse gases.

Although researchers have been studying degrading underwater permafrost for decades, the difficulty of collecting measurements and sharing data between international and disciplinary divisions has prevented a general estimate of carbon footprint and release rate. A new doctoral study. candidate Sara Sayedi and principal investigator Dr. Ben Abbott of Brigham Young University (BYU) published in IOP Publishing Environmental research letters, sheds light on submarine permafrost climate feedback, generating the first estimates of circumarctic carbon stocks, greenhouse gas release and the possible future response of the submarine permafrost area.

Sayedi and an international team of 25 permafrost researchers worked under the coordination of the Permafrost Carbon Network (PCN), which is supported by the US National Science Foundation. The researchers combined the results of published and unpublished studies to estimate the size of past and present underwater carbon stocks and the amount of greenhouse gases they could produce over the next three centuries.

Using a methodology called expert assessment, which combines multiple independent plausible values, the researchers estimated that the underwater permafrost region currently captures 60 billion tons of methane and contains 560 billion tons of organic carbon in sediment and soil. As a reference, humans have released into the atmosphere a total of about 500 billion tons of carbon since the Industrial Revolution. This makes the underwater carbon stock permafrost a potential giant ecosystem feedback on climate change.

“Submarine permafrost is truly unique because it still responds to a dramatic climate transition more than ten thousand years ago,” Sayedi said. “In some ways, it can take a look at the possible response of permafrost thawing today due to human activity.”

Estimates from Sayedi’s team suggest that submarine permafrost is already releasing substantial amounts of greenhouse gases. However, this version is mainly due to ancient climate change, rather than current human activity. They estimate that underwater permafrost releases about 140 million tons of CO₂ and 5.3 million tons of CH4 in the atmosphere each year. This is similar in magnitude to the overall greenhouse gas footprint in Spain.

The researchers found that if man-made climate change continues, the release of CH₄ and CO₂ from underwater permafrost could increase substantially. However, this response is expected to appear in the next three centuries, rather than abruptly. The researchers estimated that the amount of future greenhouse gas emissions from submarine permafrost depends directly on future human emissions. They found that in a normal scenario, underwater permafrost heating releases four times more CO₂ and CH₄ compared to when human emissions are reduced to keep the heating below 2 ° C.

“These results are important because they indicate substantial but slow climate feedback,” Sayedi explained. “Some coverage of this region has suggested that human emissions could trigger the catastrophic release of methane hydrates, but our study suggests a gradual increase over several decades.”

Although this climate feedback is relatively gradual, the researchers point out that underwater permafrost is not included in current climate agreements or greenhouse gas targets. Sayedi stressed that there is still a great deal of uncertainty about underwater permafrost and that further research is needed.

“Compared to how important underwater permafrost could be for the future climate, we know little shocking about this ecosystem,” Sayedi said. “We need more sediment and soil samples, as well as a better monitoring network to detect when greenhouse gas emissions respond to current warming and how quickly this giant carbon sink will wake up from its slumber. its ice cream. ”