Methane may be answer to 56-million-year question

Nov 09, 2011
Research at Rice University bolstered a long-controversial theory that massive amounts of carbon from methane hydrate caused the Earth to warm 56 million years ago and drastically change the ecosystem. Rice scientists proposed in a new Nature Geoscience paper that hydrates collected in a narrower stability zone than today under the seafloor over millions of years were discharged rapidly as the planet warmed, much as an electrical capacitor gathers charge and releases it quickly. (Credit Guangsheng Gu/Rice University)

(PhysOrg.com) -- The release of massive amounts of carbon from methane hydrate frozen under the seafloor 56 million years ago has been linked to the greatest change in global climate since a dinosaur-killing asteroid presumably hit Earth 9 million years earlier. New calculations by researchers at Rice University show that this long-controversial scenario is quite possible.

Nobody knows for sure what started the incident, but there's no doubt Earth's temperature rose by as much as 6 degrees Celsius. That affected the planet for up to 150,000 years, until excess carbon in the oceans and was reabsorbed into .

Earth's ecosystem changed and many species went extinct during the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago, when at least 2,500 gigatonnes of carbon, eventually in the form of carbon dioxide, were released into the and atmosphere. (The era is described in great detail in a recent National Geographic feature.)

A new report by Rice scientists in Nature suggests that at the time, even though methane-containing – the "ice that burns" – occupied only a small zone of sediment under the seabed before the PETM, there could have been as much stored then as there is now.

This is a concern to those who believe the continued burning of fossil fuels by humans could someday trigger another feedback loop that disturbs the stability of hydrate under the ocean and in permafrost; this change could warm the atmosphere and prompt the release of large amounts of methane, a more powerful greenhouse gas than carbon dioxide.

Some who study the PETM blame the worldwide burning of peat, volcanic activity or a massive asteroid strike as the source of the carbon, "but there's no crater, or any soot or evidence of the burning of peat," said Gerald Dickens, a Rice professor of science and an author of the study, who thinks the new paper bolsters the argument for hydrates.

The lead author is graduate student Guangsheng Gu; co-authors are Walter Chapman, the William W. Akers Professor in Chemical Engineering; George Hirasaki, the A.J. Hartsook Professor in Chemical Engineering; and alumnus Gaurav Bhatnagar, all of Rice; and Frederick Colwell, a professor of ocean ecology and biogeochemistry at Oregon State University.

In the ocean, organisms die, sink into the sediment and decompose into methane. Under high pressure and low temperatures, methane molecules are trapped by water, which freezes into a slushy substance known as gas hydrate that stabilizes in a narrow band under the seafloor.

Warmer oceans before the PETM would have made the stability zone for gas hydrate thinner than today, and some scientists have argued this would allow for much less hydrate than exists under the seafloor now. "If the volume – the size of the box – was less than today, how could it have released so much carbon?" Dickens asked. "Gu's solution is that the box contains a greater fraction of hydrate."

"The critics said, 'No, this can't be. It's warmer; there couldn't have been more methane hydrate,'" Hirasaki said. "But we applied the numerical model and found that if the oceans were warmer, they would contain less dissolved oxygen and the kinetics for methane formation would have been faster."

With less oxygen to consume organic matter on the way down, more sank to the ocean floor, Gu said, and there, with seafloor temperatures higher than they are today, microbes that turn organic matter into methane work faster. "Heat speeds things up," Dickens said. "It's true for almost all microbial reactions. That's why we have refrigerators."

The result is that a stability zone smaller than what exists now may have held a similar amount of methane hydrate. "You're increasing the feedstock, processing it faster and packing it in over what could have been millions of years," Dickens said.

While the event that began the carbon-discharge cycle remains a mystery, the implications are clear, Dickens said. "I've always thought of (the hydrate layer) as being like a capacitor in a circuit. It charges slowly and can release fast – and warming is the trigger. It's possible that's happening right now."

That makes it important to understand what occurred in the PETM, he said. "The amount of carbon released then is on the magnitude of what humans will add to the cycle by the end of, say, 2500. Compared to the geological timescale, that's almost instant."

"We run the risk of reproducing that big carbon-discharge event, but faster, by burning fossil fuel, and it may be severe if hydrate dissociation is triggered again," Gu said, adding that also offers the potential to become a valuable source of clean energy, as burning methane emits much less than other fossil fuels.

The calculations should encourage geologists who discounted hydrates' impact during the PETM to keep an open mind, Dickens said. "Instead of saying, 'No, this cannot be,' we're saying, 'Yes, it's certainly possible.'"


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More information: Read the abstract at www.nature.com/ngeo/journal/va… nt/abs/ngeo1301.html

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User comments : 18

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tadchem
5 / 5 (2) Nov 09, 2011
One implication of this is that gradual controlled depletion of the hydrates with subsequent conversion of the methane to a less active GHG would be desirable with regard to delay and mitigation (and possibly prevention) of a repeat event.
Sigh
5 / 5 (1) Nov 09, 2011
Yes, provided the extraction method doesn't trigger an uncontrolled release or cause a lot of other damage. I haven't yet read of any way to mine methane hydrate, so I have no idea what would happen.
Vendicar_Decarian
3.4 / 5 (5) Nov 09, 2011
If the intent is massive destruction of very large areas of the sea floor is your goal, then the strip mining of Methane Hydrates is the way to go.
Cave_Man
1 / 5 (2) Nov 09, 2011
How deleterious would methane hydrate be on organic life around significant concentrations as well as more subtle concentrations in the atmosphere?
Jeddy_Mctedder
1 / 5 (3) Nov 09, 2011
off topi but if someone is going to find out why there are seasonal warmth based releases of methane on mars..... id congradulate them, too bad the russians fucked up again .
tkjtkj
5 / 5 (1) Nov 09, 2011
off topi but if someone is going to find out why there are seasonal warmth based releases of methane on mars..... id congradulate them, too bad the russians ......
""failed"".

Despite having been forced to endure your unprofessional language i do wish you had informed us just what you mean about the referenced 'Russian' "failure".
But please keep it civil!

Vendicar_Decarian
3 / 5 (2) Nov 09, 2011
First: The Russians haven't "failed" yet. They have a few days to rectify the problem if possible.

Second: They were going to Phobos, not land on Mars, so the application of their mission to the issue discussed in the article is not possible.
Shootist
1.4 / 5 (12) Nov 09, 2011
This is a concern to those who believe the continued burning of fossil fuels by humans could someday trigger another feedback loop that disturbs the stability of methane hydrate under the ocean and in permafrost; this change could warm the atmosphere and prompt the release of large amounts of methane, a more powerful greenhouse gas than carbon dioxide.


Anything to keep the crisis going.

Oh,
the Ruskies failed all right,
again,
without a doubt.
Au-Pu
3.7 / 5 (6) Nov 09, 2011
What a collection of poorly developed opinions.
All the above postings should be deleted.
Not one of them makes any sense.
All they do is to strut egos.
JohnW
3 / 5 (1) Nov 09, 2011
We accept that methane hydrates are abundant under the ocean. The issue is how to safely and efficiently mine them.
It seems that dredging with an "air lift" pump would lift the silt containing the hydrates toward shallower depths. The air-lift would have to be purged and operated by methane gas. Mechanical scrapers would disturb the selected portion of ocean floor. (Likely restricted to a nearly-horizontal bottom surface.) As the solids are lifted toward the surface, the three-phase mixture is in turbulent mixing, with pressure decreasing and being warmed by shallower water contact outside the dredge pipe. Before reaching the surface, the mix containing methane gas, hydrate and silt, would pass through a cyclone device. This device would direct the solids back toward an appropriate location on the ocean floor. The original methane, plus the released dissociated methane from hydrates would continue toward the surface for collection. The system would likely become self-pumping, with rel
rwinners
1 / 5 (2) Nov 09, 2011
If this scenario proves true, what is to prevent it?
Burnerjack
4 / 5 (4) Nov 09, 2011
It just may be that the planet's natural proccesses are too big for us to control and we might be better off accepting then instead of fighting them. Thr plane was here before us and will be here after we're gone.
CWFlink
not rated yet Nov 09, 2011
Note that understanding this methane cycle and exploiting it potentially provides for a renewable (and virtually infinite) source of "green" energy. Methane is the closest fuel to providing the ideal of a "hydrogen economy". And now we see what CO2 is released in burning hydrates can be returned to the deep where bacteria converts it back to methane?!

The "crime" in burning fossil fuels is that it adds to CO2 levels in the atmosphere... Releasing energy sequestered in stone eons ago. Here we have a process that potentially is much quicker to turn around.

I was fascinated watching the methane hydrates "gum up the works" as engineers tried to seal the leaks on the ocean floor after the Gulf Horizon (sp?) summer before last. ...also stunned to discover deep sea bacteria devoured the bulk of the massive oil spill before it reached the surface. I think there is great potential for sequestering our excessive CO2 in the deep ocean and finding microbes that will turn it into methane!
unknownorgin
1 / 5 (3) Nov 10, 2011
Unless my numbers are way off 2500 gigatons is less than .01 percent of the weight of the atmosphere.

rwinners
1 / 5 (2) Nov 14, 2011
What was happening geologically and tectonically 56 million years ago?
Vendicar_Decarian
3 / 5 (2) Nov 14, 2011
But it would only take 30 gigatons of aluminum foil spread evenly over the earth to blocking all sunlight from reaching the earth's surface.

35 gigatons is only 3 times the world annual production of CO2. Can you explain to us how such a minuscule amount of material could immediately cool the earth's surface to absolute zero?

Curious minds want to know.

"Unless my numbers are way off 2500 gigatons is less than .01 percent of the weight of the atmosphere." - UnKnown
Vendicar_Decarian
3 / 5 (2) Nov 14, 2011
"It just may be that the planet's natural proccesses are too big for us to control" - BumperTard

Since we are the perturbative force producing the warming your initial premise has already been falsified.

You no Edgimacation Muchlie?

Vendicar_Decarian
3 / 5 (2) Nov 14, 2011

Wouldn't that kill ever living thing in and on the ocean sediment being dredged?

"It seems that dredging with an "air lift" pump would lift the silt containing the hydrates toward shallower depths." - JohnWTard