Fire-ice, or methane hydrate, is a fascinating phenomenon in which natural gas becomes trapped in a frozen, solid state deep beneath the ocean floor. This compound is formed as a result of the combination of methane, a potent greenhouse gas, and water, which together create an ice-like structure. Recent research published in Nature Geoscience has uncovered evidence that this fire-ice has previously thawed during periods of historical climate warming, releasing large quantities of methane into the atmosphere.
Ongoing concerns about the impact of human-driven climate change pose the question of how this fire-ice may respond to increasing ocean temperatures. The potential melting of these methane hydrates and subsequent methane release could have significant ramifications for our environment. As technology advances, scientists and researchers from organizations, such as the Department of Energy, are working on developing methods to harness and utilize this hydrocarbon as an energy source, while also considering the challenges associated with mining and flammability.
Why is Methane a Problem?
Methane is responsible for approximately 16% of global greenhouse gas emissions and is the second most abundant greenhouse gas after carbon dioxide. Although it has a shorter lifespan in the atmosphere, it is 25 times more effective than carbon dioxide in trapping heat, leading to increased global temperatures.
Significant sources of methane include agriculture and decomposition processes in marshes, landfills, and fossil fuels. In 2021, the Intergovernmental Panel on Climate Change (IPCC) recognized methane emissions as a priority for tackling climate change in the upcoming decade.
One concerning form of methane release is from “fire ice,” or methane hydrates, which are frozen deposits found deep beneath the ocean floor. Scientists believe that thawing fire ice has contributed to past climate changes and has been linked to ocean warming in the Southern Hemisphere.
Addressing methane emissions is crucial in the fight against climate change, as reducing atmospheric methane concentrations can help slow down global warming and its impacts on the Earth’s environment. Consequently, it is essential for scientists, policymakers, and industries to actively work on mitigating methane emissions for the benefit of our planet.
Exploring the Pockmarks
An international group of researchers utilized advanced 3D seismic imaging techniques to examine a section of methane hydrates, also known as “fire-ice,” near the coast of Mauritania in Africa. The Department of Energy identifies such gas hydrates as immense sources of methane, containing somewhere between 250,000 to 700,000 trillion cubic feet.
In their investigation, scientists discovered an instance in which methane traveled over 25 miles from the deeper areas of the continental slope toward the edge of the underwater shelf. This could have happened during past warming periods over 2.6 million years, when the fire-ice began to thaw and the methane possibly escaped to the ocean through a field of underwater depressions called pockmarks.
Richard Davies, a study co-author and petroleum geologist at Newcastle University, highlighted the significance of these findings: “Scientists had previously thought this hydrate was not vulnerable to climatic warming, but we have shown that some of it is.”
Previous investigations explored how variations in bottom water temperature near continental margins might impact the release of methane from hydrates. However, those studies mainly focused on a smaller portion of global methane hydrates in shallower regions. This study examined methane release from the base of the hydrate stability zone, an area of the ocean ranging from 1,476 to 2,296 feet deep. The researchers found that methane from this zone traveled significantly towards land.
Christian Berndt, a study co-author and geophysicist at the GEOMAR research institute in Germany emphasizes the importance of the discovery: “So far, research efforts focused on the shallowest parts of the hydrate stability zone, because we thought that only this portion is sensitive to climate variations. The new data clearly show that far larger volumes of methane may be liberated from marine hydrates and we really have to get to the bottom of this to understand better the role of hydrates in the climate system.”