Melting Fire Ice Contributes to Climate Change; Hydrate Dissociation Spotted Due to Pockmarks

Fire ice underwater is melting, and it may have contributed to global warming. It has been releasing methane that travels under the seafloor, warming the water.

Melting Fire Ice Underwater May Have Contributed To Climate Change

Richard Davies of Newcastle University had 3D images of the underwater sedimentary strata in the Atlantic Ocean off the coast of Mauritania. During the COVID lockdown, he checked the images and noticed pockmarks on the seafloor. He observed about 23, each a kilometer wide and 50 meters (164 feet) deep.

These structures usually result from extensive gas venting, throwing silt upward, and forming divots. Davies studies marine methane hydrate, sometimes called fire ice, one of the planet's most peculiar natural materials.

Methane gas and liquid water freeze beneath the seafloor at low enough temperatures and high enough pressure to produce an ice-like structure resembling marshmallows.

The cold, gaseous fragments have been fitted together by Davies and his colleagues in a new study to explore the potential contribution of this strange material to climate change, not due to burning but rather due to melting.

It "dissociates" during its natural melting process, generating methane that either dissolves in the seawater or bubbles to the surface. The pockmarks his team observed in their photos were most likely caused by climate change a million years ago or less.

The divots formed when fire ice melted and released gas that rose in the sediment and exploded from the seafloor. It looks like a single methane pocket has gone 40 kilometers (25 miles).

The research implies that a much larger portion of fire ice than previously thought is susceptible to melting due to climate change and that this ice may eventually contribute significantly to greenhouse gas emissions.

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Methane From Fire Ice And Global Warming

Below 750 meters, hydrate is thought to be stable and is unlikely to leak methane into the ocean due to climate change.

Davies believes that very deep fire ice, possibly several hundred meters below the seabed at water depths of one to two kilometers, also warmed and became unstable during the previous million years of ocean warming. This, he believes, released gas that began to flow upslope.

At about 330 meters, the methane started to leak as it moved from deeper locations beneath the seafloor. The gas moves upslope through the bottom to shallower waters, dissociating fire ice. It may be able to bubble up via pockmarks and reach the stratosphere.

There is a risk that the excess methane will start a climate feedback cycle. Permafrost is thawing as the Arctic warms up to four times faster than the rest of the Earth.

This might cause warming and lead the permafrost to defrost. Fire ice under the sea might do the same thing. It could melt, release more methane and the climate would get warmer.

However, depth is critical to consider when discussing methane gas and climate. Fire ice may split apart and release methane into the ocean's deepest regions, but microorganisms will eat the gas before it can reach the surface.

Additionally, methane dissolves easily in seawater, which will acidify it but keep it from entering the atmosphere.