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Researchers from Newcastle University have produced a new study that demonstrates how vulnerable fire-ice—frozen methane sealed as a solid underneath our oceans—is to melting as a result of climate change and potentially spilling into the ocean. According to this study published in the journal Nature Geoscience, this suggests that as a result of climate change, a lot more methane may be vulnerable and released into the atmosphere.



The methane-containing ice-like structure called methane hydrate, or fire-ice, is buried beneath the ocean floor. Under the oceans, marine methane stores enormous volumes of methane. Dissociated methane, which is released into the atmosphere and oceans when the oceans warm, causes it to thaw and contributes to global warming. The scientists examined the piece of the hydrate that dissociated during climatic warming off the coast of Mauritania in Northwest Africa using sophisticated three-dimensional seismic imaging techniques. They pinpointed a particular instance in which, during previous warm periods, dissociated methane traveled almost 40 km and was released through a field of underwater depressions known as pockmarks.



Leading author Professor Richard Davies, Pro-Vice-Chancellor, Global and Sustainability, Newcastle University, stated, "It was a Covid lockdown discovery; I pretty much stumbled over 23 pockmarks when I revisited imaging of strata just under the modern seafloor offshore of Mauritania. According to our research, they originated as a result of methane spewing out of hydrate and venting into the ocean from the lowest points of the continental slope. It was previously believed by scientists that this hydrate was not susceptible to climate change, but our findings indicate that a portion of it is.”



Methane Hydrate

The impact of temperature variations in the bottom water close to continental boundaries on methane release from hydrates has been the subject of earlier research. Still, the majority of these investigations were conducted in regions that contain a relatively modest fraction of the world's methane hydrates. This is one of very few that look into the methane emission from the deeper underwater base of the hydrate stability zone. The findings indicate that a considerable amount of methane that was released from the hydrate stability zone moved in the direction of land.



The Head of Kiel, Germany's GEOMAR Research Unit Marine Geodynamics, Professor Dr. Christian Berndt, continued, "This is an important discovery." Until now, studies have concentrated on the shallowest regions of the hydrate stability zone because we believed that these are the only areas that are affected by changes in the climate. The latest findings unequivocally demonstrate that far greater amounts of methane could be released from marine hydrates, and further research is necessary to fully comprehend this phenomenon and the function of hydrates in the climate system.



After carbon dioxide (CO2), methane is the second most prevalent anthropogenic greenhouse gas. According to data from the US Environmental Protection Agency, methane makes up roughly 16% of greenhouse gas emissions worldwide.



The findings of this study may be very helpful in predicting and mitigating the effects of methane on our changing climate. As the earth warms, the team intends to keep looking for signs of methane vents along the margin and attempting to forecast the locations of major methane seeps. To dig deeper into the pockmarks and try to establish a stronger connection between them and previous instances of global warming, the researchers are currently organising a scientific cruise.



Reference: Davies, R. J., Yang, J., Ireland, M. T., Berndt, C., Morales Maqueda, M. Á., & Huuse, M. (2023). Long-distance migration and venting of methane after marine hydrate dissociation. Nature Geoscience. doi:10.1038/s41561-023-01333