Gas Hydrate Breakdown Unlikely to Cause Massive Greenhouse Gas Release

[OKIsItJustMe]

(Please note, USGS release. Copyright concerns are nil.)

https://www.usgs.gov/news/gas-hydrate-breakdown-unlikely-cause-massive-greenhouse-gas-release

[font face=Serif][font size=5]Gas Hydrate Breakdown Unlikely to Cause Massive Greenhouse Gas Release[/font]

Release Date: February 9, 2017

[font size=4]A recent interpretive review of scientific literature performed by the U.S. Geological Survey and the University of Rochester sheds light on the interactions of gas hydrates and climate.[/font]

[font size=3]The breakdown of methane hydrates due to warming climate is unlikely to lead to massive amounts of methane being released to the atmosphere, according to a recent interpretive review of scientific literature performed by the U.S. Geological Survey and the University of Rochester.

Methane hydrate, which is also referred to as gas hydrate, is a naturally-occurring, ice-like form of methane and water that is stable within a narrow range of pressure and temperature conditions. These conditions are mostly found in undersea sediments at water depths greater than 1000 to 1650 ft and in and beneath permafrost (permanently frozen ground) at high latitudes. Methane hydrates are distinct from conventional natural gas, shale gas, and coalbed methane reservoirs and are not currently exploited for energy production, either in the United States or the rest of the world.

On a global scale, gas hydrate deposits store enormous amounts of methane at relatively shallow depths, making them particularly susceptible to the changes in temperature that accompany climate change. Methane itself is also a potent greenhouse gas, and some researchers have suggested that methane released by the breakdown of gas hydrate during past climate events may have exacerbated global warming.

Summary of the locations where gas hydrate occurs beneath the seafloor, in permafrost areas, and beneath some ice sheets, along with the processes (shown in red) that destroy methane (sinks) in the sediments, ocean, and atmosphere. The differently colored circles denote different sources of methane. Gas hydrates are likely breaking down now on shallow continental shelves in the Arctic Ocean and at the feather edge of gas hydrate stability on continental margins (1000-1650 feet). Credit: Ruppel and Kessler (2017). (Public domain.)

The new review concludes that current warming of ocean waters is likely causing gas hydrate deposits to break down at some locations. However, not only are the annual emissions of methane to the ocean from degrading gas hydrates far smaller than greenhouse gas emissions to the atmosphere from human activities, but most of the methane released by gas hydrates never reaches the atmosphere. Instead, the methane often remains in the undersea sediments, dissolves in the ocean, or is converted to carbon dioxide by microbes in the sediments or water column.

The review pays particular attention to gas hydrates beneath the Arctic Ocean, where some studies have observed elevated rates of methane transfer between the ocean and the atmosphere. As noted by the authors, the methane being emitted to the atmosphere in the Arctic Ocean has not been directly traced to the breakdown of gas hydrate in response to recent climate change, nor as a consequence of longer-term warming since the end of the last Ice Age.

“Our review is the culmination of nearly a decade of original research by the USGS, my coauthor Professor John Kessler at the University of Rochester, and many other groups in the community,” said USGS geophysicist Carolyn Ruppel, who is the paper’s lead author and oversees the USGS Gas Hydrates Project. “After so many years spent determining where gas hydrates are breaking down and measuring methane flux at the sea-air interface, we suggest that conclusive evidence for release of hydrate-related methane to the atmosphere is lacking.”

…

The paper, “The Interaction of Climate Change and Methane Hydrates," by C. Ruppel and J. Kessler, is published in Reviews of Geophysics and is available here. The USGS and University of Rochester research that contributed to the review was largely supported by the U.S. Department of Energy and the National Science Foundation.

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http://dx.doi.org/10.1002/2016RG000534

[mackdaddy]

1. This is some (mostly) good news when everything seems "Worse than previously expected".

I skimmed the original article, and Dr. Paul Beckwith did a six part youtube video series going over the whole paper.
My take is that there may not be as much methane-hydrate (methane frozen in a water lattice) as earlier studies estimated. So instead to enough methane to increase the green house gas load already released by hundreds of times it could only be increased by many tens of times.

They also go into quite a bit of detail as how and where the hydrates are found is fairly diverse and complex. Different strata underseas and on land and at different depths. The good news is that much of the methane-hydrate is located that is will take time for it to actually melt and release the methane, so a large fast release from this source is less likely.

Some of the problems though are what the paper does not directly address. First is the extreme temperature rise we have seen over the arctic. The arctic had been seeing temperatures 30C above average and the arctic ocean may be ice free this summer or next, and then all that heat may go into melting the hydrates. The paper talked about a few degrees C increase, but not these extreme increases.

The other thing they went on quite a bit about is that much of the methane released slowly from the melting hydrates would either be broken down chemically or biologically or would be dissolved and absorbed by the ocean before it would be released into the atmosphere as Methane gas. They did not detail what this would do to the ocean by displacing oxygen, and increasing the acidity of the water. Much of the paper went into basically how fast the methane was released and how big the bubbles were , and how deep they started out would determine whether the Methane gas reached the surface.

The last thing they only touched on was the other stores of methane not in hydrate form. Methane can be release from decomposing bio material like peat, and can also be trapped under layers of permafrost, ice or mud. These could also be substantial sources of sudden releases of methane as these layers melt or otherwise let go. We have been see this in the "pingos" or large craters blown out of the tundra, and in large gas plumes observed bubbling up from shallow ocean shelves. These sources could still be really bad, too.

Links: Paul Beckwith video. This is part six of six but you can link to the other parts from this summation. The last 3 minutes also gives his summation of not covered issues.

An article on a Russian study of Increases of Observed methane releases.
http://siberiantimes.com/ecology/others/news/n0760-arctic-methane-gas-emission-significantly-increased-since-2014-major-new-research/