New research has shown that frozen methane emissions are vulnerable to melting due to climate change and could be released into the sea.
An international team of researchers led by Newcastle University found that as frozen methane emissions and ice melt, methane is released and moves from the deepest parts of the continental slope to the edge of the underwater shelf.
They even discovered a pocket which had moved 25 miles (40km). The researchers said this means that much more methane could potentially be vulnerable and released into the atmosphere due to climate warming.
The research, ‘Long-distance migration and venting of methane from the base of the hydrate stability zone,’ is published in Nature Geoscience.
How methane emissions contribute to climate warming
Methane hydrate, or fire-ice, is an ice-like structure containing methane buried in the ocean floor.
Vast amounts of methane emissions are stored as marine methane under oceans. It thaws when the oceans warm, releasing methane into oceans and the atmosphere – known as dissociated methane – contributing to global warming.
The scientists used advanced three-dimensional seismic imaging techniques to examine the portion of the hydrate that dissociated during climatic warming off the coast of Mauritania in Northwest Africa.
They identified a case where dissociated methane emissions migrated over 40km and were released through a field of underwater depressions known as pockmarks during past warm periods.
Professor Richard Davies, lead author of the study, said: “I revisited imaging of strata just under the modern seafloor offshore of Mauritania and 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.
“Scientists had previously thought this hydrate was not vulnerable to climatic warming, but we have shown that some of it is.”
The methane is getting closer to land
Researchers have previously studied how changes in bottom water temperature near continental margins can affect the release of methane emissions from hydrates.
However, these studies mainly focused on areas where only a small portion of global methane hydrates are located.
This is one of only a small number that investigates the release of methane from the base of the hydrate stability zone, which is deeper underwater. The results show that methane released from the hydrate stability zone travelled significantly towards land.
“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,” stated Professor Dr Christian Berndt, Head of the Research Unit Marine Geodynamics, GEOMAR, in Kiel, Germany.
“The new data clearly show that far larger volumes of methane emissions may be liberated from marine hydrates. We really have to get to the bottom of this to understand better the role of hydrates in the climate system.”
The study results can play a crucial role in helping predict and address methane’s impact on our changing climate.
Future uses of the study
The team plans to continue to search for evidence of methane vents along the margin and try to predict where massive methane seeps are likely to occur as we warm the planet.
The researchers are now planning a scientific cruise to drill into the pockmarks and see if they can more closely tie them to past climatic warming events.
