In the far north, the swollen Arctic Ocean has flooded vast parts of the tundra and steppe coastal ecosystems. Although the ocean water was only a few degrees above freezing, it began to melt the eternal frost beneath it, exposing billions of tons of organic matter to microbial decomposition. The decomposing organic matter began to produce CO2 and CH4, the two most important greenhouse gases.
Although researchers have studied the humiliation of submarine permafrost for decades, difficulties in collecting measurements and sharing data between international and disciplinary divisions have prevented an overall assessment of carbon emissions and discharge rates. The new study, led by Ph.D. candidate Sara Sayedi and researcher dr. Ben Abbott of Brigham Young University (BYU) published in IOP Publishing Letters on environmental research, illuminates feedback on submarine permafrost, generating first estimates of carbon stocks in the circummark, the release of greenhouse gases, and a possible future response to the submarine permafrost zone.
Sayedi and an international team of 25 permafrost researchers worked under the coordination of the Permafrost Carbon Network (PCN), supported by the American National Science Foundation. The researchers combined the findings of published and unpublished studies to estimate the size of past and present submarine carbon stocks and how much greenhouse gases it could produce in the next three centuries.
Using a methodology called expert assessment, which combines multiple, independent credible values, the researchers estimated that the submarine permafrost region currently traps 60 billion tons of methane and contains 560 billion tons of organic carbon in sediment and soil. For reference, humans have released about 500 billion tons of carbon into the atmosphere since the Industrial Revolution. This makes the submarine carbon stock permafrost a potential giant ecosystem feedback on climate change.
“Underwater perpetual frost is truly unique because it still responds to the dramatic climate transition of more than ten thousand years ago,” Sayedi said. “In a way, it can give us a peek into the possible response of the eternal ice that is melting today due to human activity.”
Estimates by Sayedi’s team suggest that underwater perpetual frost is already releasing significant amounts of greenhouse gases. However, this release is largely due to ancient climate change, not current human activity. It is estimated that underwater perpetual frost emits approximately 140 million tons of CO2 and 5.3 million tons of CH4 into the atmosphere every year. This is similar in size to the total greenhouse gas footprint in Spain.
Researchers have found that if man-made climate change continues, the release of CH4 and CO2 from submarine permafrost could increase significantly. However, this response is expected to happen in the next three centuries, not abruptly. The researchers estimated that the amount of future greenhouse gas emissions from submarine permafrost is directly dependent on future human emissions. They found that under the usual scenario, warming underwater permafrost releases four times more CO2 and CH4 compared to reducing human emissions to keep warming below 2 ° C.
“These results are important because they indicate significant but slow climate feedback,” Sayedi explained. “Some covers of this region suggest that human emissions could cause a catastrophic release of methane carbohydrates, but our study suggests a gradual increase over many decades.”
Even if this climate feedback is relatively gradual, researchers point out that submarine permafrost is not included in any current climate agreement or greenhouse gas targets. Sayedi stressed that there is still a large amount of uncertainty around submarine permafrost and that further research is needed.
“Given the importance of underwater permafrost for the future climate, we know shockingly little 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 react to instantaneous warming and how quickly this huge pool of carbon will wake up from its frozen sleep.”
This research was funded by the American National Science Foundation and BYU graduate studies.
Summary of key scientific views:
- Submarine perpetual frost has been melting since the end of the last glacial period (~ 14,000 years ago) when the ocean began to flood it
- An international team of 25 permafrost researchers estimates that the submarine region of permafrost currently traps 60 billion tons of methane and 560 billion tons of organic carbon in sediment and soil. However, the exact amount of these carbon stocks remains very uncertain.
- This carbon is already being released from the submarine permafrost area, although it remains unclear whether this is a natural response to deglation or anthropogenic warming accelerates greenhouse gas production and release.
- Researchers estimate that the current submarine area of permafrost releases approximately 140 million tons of CO2 and 5.3 million tons of CH4 into the atmosphere every year. This represents a small fraction of total anthropogenic greenhouse gas emissions – roughly equal to the greenhouse gas footprint in Spain.
- Experts predict a gradual increase in emissions from submarine permafrost over the next three hundred years, rather than a sudden release.
- The amount of increase in greenhouse gases depends on how much human emissions are reduced. Experts estimate that approximately ¾ additional submarine emissions can be avoided if people actively reduce emissions compared to the non-mitigation scenario.
- This climate feedback is still virtually non-existent in climate policy discussions, and more field observations are needed to better predict the future of this system.
Source of the story:
Material provided IOP Publishing. Original written by Rachael Harper. Note: Content can be edited for style and length.