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Antarctic Methane: A New Factor in the Climate Equation

Climate scientists have long fretted about the hundreds of billions of tons of methane frozen under the floor of the Arctic Ocean. If the water warms enough, some of that methane could escape. Nobody knows how soon or how quickly such a release might happen, but since methane is a far more potent heat-trapping gas than the more familiar carbon dioxide, it could add to the temperature increase already under way thanks largely to human emissions from fossil fuel burning. 

But frozen Arctic methane turns out to be just the tip of the iceberg, so to speak. According to a paper released Wednesday in Nature, there could be just as much methane trapped on the opposite side of the planet, under Antarctica’s vast ice sheets.

Icebergs form on ice sheets in Antarctica.
Credit: NASA

“It’s very hard to say what the effect would be if it were released,” said lead author Jemma Wadham, of the University of Bristol, in an interview. “And it’s hard to say when it might happen, and where. But there is potential for a release, for sure.”

Wadham and her colleagues didn’t actually detect the Antarctic methane directly. What they did do was to prove that the frozen continent has all the right conditions in place to make methane deposits a very likely bet.

The first link in their chain of reasoning is the fact that Antarctica was largely ice-free millions of years ago, sporting lush forests that eventually decomposed to form soil rich in organic matter. Parts of West Antarctica were open water, where marine life created similarly rich sediments at the bottom of the sea — sediments that are up to eight miles thick in some places, with thousands of feet of ice on top of them. 

In principle, bacteria should have decomposed some of these vast storehouses of organic matter into methane. The methane should bubble up to the undersides of the ice sheets. Once there, the freezing cold and high pressure of the overlying ice should have transformed them into deposits known as methane hydrates, the same formations scientists know are trapped on the continental shelves of the Arctic Ocean.

What scientists didn’t know was whether this bacterial decomposition actually happened, even if the textbooks said it should. So Wadham and her co-authors took soil samples from the margins of glaciers in both Antarctica and Greenland. “We spent a couple of years chain-sawing out sediments frozen into the bottom of the ice,” she said, adding with a connoisseur’s judgment, “They were very nicely preserved.”

Antarctica.
Credit: NASA.

They hauled the samples back to the lab and allowed them to thaw under carefully controlled, oxygen-deprived conditions where oxygen-hating, methane-belching bacteria known as methanogens could do their work — assuming they were there. And sure enough, the soil began producing methane.

The same thing should presumably be happening underneath Antarctica’s ice, where heat percolating from the depths of the Earth have prevented sediments from ever having frozen. 

“You have perfect conditions, and the ice has been there for 30 million years,” Wadham said, “so there’s been plenty of time for methane to build up.”

It takes a combination of cold and pressure to turn methane into methane hydrates, and if either one of these conditions is relaxed, the methane can escape. In the Arctic, it’s the loss of cold scientists worry about as the seawater overlying methane-rich sediments continues to warm

In the Antarctic, Wadham said, “it’s the drop in pressure that would come if the ice sheets get thinner.” It’s not happening yet, but that could change if the temperature of waters surrounding the Antarctic continent continues to rise.

Wadham emphasized that the threat remains theoretical at this point. Not only is it unclear whether Antarctica’s ice sheets might get substantially thinner, or when it could happen, but nobody has proven that methane hydrate deposits lie below them. The new study simply provides one strong link in a chain that is still being forged.

It’s clear, however, that the forging process needs to continue. “We need people to drill to the bottom of the ice sheets to find out what’s actually going on,” Wadham said.  

Comments

By Jack Burton (Two Harbors, MN, 55616)
on August 29th, 2012

I thought that the Russian Academy of Science announced many months back that they have detected giant methane plumes rising from the waters off of Eastern Siberia. They said in the past plumes existed there but were only meters across in width. Last year they discovered many plumes, too many to count in such vast seas, that were no kilometers across in width.
This Russian scientific organization has long taken a weak position on human induced global warming, being that Russia’s main export commodity is fossil fuel in the form of gas and oil.
In any case, they now claimed to be shocked by the sudden increase in the size of the methane plumes and the large expanse of waters that they exist in. It takes a lot to SHOCK people who are used to fossil fuel being their main income source! So yes, I don’t know why scientists speculate that maybe the methane will begin to be released, It already is! And as usual the press is missing in action. No doubt bought off by the fossil fuel industry advertisers.
My take on this is “The feed back loops are already in full swing”. It is just that everyone who knows it has been intimidated into being very circumspect about going too public. When even the Russians are announcing publicly that they are shocked and the USA media is silent, that tells you the US media has been “gotten to”.
We are in deep trouble, and silence is all we get. Look at Greenland’s melting! Look at arctic sea ice melting, look at world glacial melting! The arctic feedback of open dark sea water replacing reflective ice and the methane down below beginning to spew forth is about all the evidence I need.
It might just be time to panic. What will it take to wake up the bought off US media?

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By Bill Carpenter (Tawas City, MI 48763)
on August 30th, 2012

I’m with you, Jack. I think the shelling the press gets from mentioning even the possibilities probably helps keep them down.  But that can be an excuse, too.  There is plenty of evidence emerging, month after month.

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By Alan Vallis (New Zealand)
on August 30th, 2012

@ Jack Burton,

You are absolutely correct Jack, it’s beyond astonishing that this potentially catastrophic situation is being ignored by the mainstream media.

http://www.dailymail.co.uk/sciencetech/article-2073686/Fountains-methane-1-000m-erupt-Arctic-ice—greenhouse-gas-30-times-potent-carbon-dioxide.html

http://thinkprogress.org/climate/2010/03/04/205600/science-nsf-tundra-permafrost-methane-east-siberian-arctic-shelf-venting/?mobile=nc

Climate change, the demand for exponential economic growth, peak everything, the dysfunctional monetary system, the failure of party politics and the control of media and politicians by big business are inextricably interlinked. Add to that the abject failure of the western world’s educational system and you have a recipe for Armageddon.

The 99% have the power but are too stupid, apathetic and misguided to use it.

“Do you not know, my son, with how little wisdom the world is governed?”
Axel Gustafsson Oxenstierna af Södermöre

“We have the best government that money can buy.”
Mark Twain

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By William Hughes-Games (Waipara New Zealand 7447)
on August 30th, 2012

Methane is also released from coal, shale and liquid hydrocarbon deposits.  This carbon is usually incorporated into the biosphere as it is released.  With the land covered by an ice sheet, it would accumulate until the ice melts.
http://mtkass.blogspot.co.nz/2011/09/continental-glacier-meltdown.html

Reply to this comment

By Larry Oliver a/k/a @tweetingdonal
on August 30th, 2012

Just a follow up comment to some of the earlier comments. This discussion is about methane deposits in and around the Antarctic, formed under very old ice.

Borrowing a comment from the folks at Real Climate: “Methane is like the radical wing of the carbon cycle, in today’s atmosphere a stronger greenhouse gas per molecule than CO2, and an atmospheric concentration that can change more quickly than CO2 can.”

Methane seeps have been noted in the Arctic in many places for years, and yes, there is a real reason to be concerned about methane’s contribution to the carbon gases cycling around. It is shorter lived, but very effective while it’s around, about 20 times more potent as a heat “trapping” gas than carbon dioxide. Being less stable, it just doesn’t stay present as methane as long as carbon dioxide can.

Rather than panic over somewhat theoretical methane that could exit one day in Antarctica, let’s amp up some attention to the melting that IS happening and measurable in the Arctic, with multiple disastrous effects already. You’ve already cited what few mentions there have been in the media about this, find a way to support the work of people like the International Arctic Research Center and Professor Sharkova who’s work you were citing ( http://www.iarc.uaf.edu/people/nshakhov )

Panic is a waste of energy. Find a way to help get the word out.

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By Richard Lawson (Churchill, N Somerset, UK BS25 5NT)
on September 5th, 2012

How much would these deposits, if released, add to the existing methane content of the atmosphere? And how long would it take for the new addition to be neutralised through oxidation? In other words, what is the estimated contribution of these methane deposits to future global warming?

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By Gerald Spezio (Willits, CA)
on October 14th, 2012

It is almost one full year since Semelitov discovered the 1000 meter diameter methane plumes in the arctic.
Lemonick’s article here is one very few articles to date even mentioning the plumes in mass media.
Of course, Semelitov & Shakova have more data about the plumes, especially their probable increase, but WE ARE NOT SEEING IT!
THIS IS CAUSE FOR ALARM.

Reply to this comment

By Ian Wallace (Sheffield, United Kingdom, S7 1PF)
on June 18th, 2013

Here in South Yorkshire we used to have a system of very cheap public transport. We paid for it collectively through the rates, which were therefore quite high, but most people saved far more on fares than they spent on the rates so most people liked it very much. The result was that car usage (and associated emissions) were greatly reduced. Many people observed that it would have been cheaper to make all public transport free, rather than continue with all the costs of ticketing.
I have just heard on the World Service that mass demonstrations are taking place in Brazil against the rising costs (to pay for a football tournament) of public transport.
Making all public transport free (and very, very good) would have benefits far beyond the cost of travelling.

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