Climate change could melt the frozen methane trapped under oceans, releasing the potent greenhouse gas, methane, into these water bodies, researchers have found. They said that as frozen methane and ice melted, methane moved from the deepest parts of the continental slope to the edge of the underwater shelf.
The researchers led by Newcastle University, UK, also discovered a pocket of the released methane, which they said had moved about 25 miles, or 40 kilometres. This meant that more methane could potentially be vulnerable and released into the atmosphere as a result of climate warming, the researchers said in their study published in the journal Nature Geoscience.
Frozen methane is an ice-like structure
Frozen methane refers to the compound methane hydrate, an ice-like structure found buried in the ocean floor. As the oceans warm, these structures thaw, thereby releasing the methane into the oceans and the atmosphere as dissociated methane and contributing to global warming. Methane is the second most abundant human activity-driven greenhouse gas after carbon dioxide (CO2).
"Scientists had previously thought this hydrate was not vulnerable to climatic warming, but we have shown that some of it is," said lead author Richard Davies, Newcastle University. Previous studies have shown bottom water temperature changes near continental margins to affect the release of methane from the frozen structures. However, these studies mainly focused on areas where only a small portion of global methane hydrates are located, the researchers said.
This is an important discovery, according to experts
Their study was one of those few which investigate the release of methane from the base of the hydrate stability zone, which is deeper underwater, they said. "This is an important discovery. 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," said Christian Berndt, Head of the Research Unit Marine Geodynamics, GEOMAR, in Kiel, Germany.
Dissociated methane migrated over 40 kilometres, as per researchers
The scientists examined the portion of the hydrate that dissociated under warming climate off the coast of Mauritania in Northwest Africa using seismic imaging techniques. They found that the dissociated methane had migrated over 40 kilometres and was released through a field of underwater depressions, known as pockmarks, during past warm periods.
"It was a Covid lockdown discovery, I revisited imaging of strata just under the modern seafloor offshore of Mauritania and pretty much stumbled over 23 pockmarks. Our work shows they formed because methane released from hydrate, from the deepest parts of the continental slope vented into the ocean," said Davies. The researchers said that the study findings could help in predicting and addressing the impact of methane on our changing climate.