Melting "fire-ice" unleashes deep methane from beneath the seafloor

Climate change is increasingly recognized as a critical global issue, and a recent study has shed new light on one of its less understood consequences: the release of methane from deep ocean sources. 

The research reveals that a frozen form of methane trapped deep in the ocean is melting and releasing the potent gas due to climate warming.

Methane hydrate

The study was conducted by an international team of researchers who used advanced three-dimensional seismic imaging techniques. They focused on the dissociation of methane hydrate, also known as fire-ice, off the coast of Mauritania in Northwest Africa. 

Methane hydrate is an ice-like substance containing methane, stored in large quantities under the ocean floor. As the oceans warm, this methane thaws and releases both into the sea and the atmosphere, contributing to global warming.

Unexpected deep sea methane discovery

The study findings are significant. In one particular case, dissociated methane migrated over 40 kilometers from the deepest parts of the continental slope, released through pockmarks on the ocean floor. 

This discovery challenges the previous assumption that hydrate in such deep regions was not vulnerable to climatic warming. Study lead author Professor Richard Davies of Newcastle University noted the unexpected nature of this discovery.

“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,” said Professor Davies.

“Our work shows they formed because methane released from hydrate, from the deepest parts of the continental slope vented into the ocean. Scientists had previously thought this hydrate was not vulnerable to climatic warming, but we have shown that some of it is.”

Hydrate stability zone 

The study indicates that even deep-seated methane hydrate is susceptible to climate change, and its release can significantly impact the atmosphere.

“This is an important 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,” said Dr. Christian Berndt of GEOMAR in Kiel, Germany.

“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.”

Deep sea methane implications 

Methane is a potent greenhouse gas, second only to carbon dioxide in its abundance and impact. According to the United States Environmental Protection Agency, methane constitutes about 16 percent of global greenhouse gas emissions. Thus, understanding and addressing methane release is crucial for climate change mitigation.

The study’s results are pivotal in predicting and managing the impact of methane on our changing climate.

The research team plans to continue investigating methane vents along ocean margins and aims to forecast areas where massive methane seeps could occur due to planetary warming. They are now organizing a scientific cruise to drill into the pockmarks and establish a closer link to past climatic warming events.

The research is published in the journal Nature Geoscience.

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