December 2009 - Permafrost and methane - a chilling story
Two separate but connected issues, permafrost and methane, have become a focus of study for many climate change researchers recently.
Scientists from Russia (Siberia), the United States (Alaska), Canada (Arctic) and Scandinavia are coming together to study this confluence as a potentially important factor in global warming.
First some background. Permafrost by definition is any ground that is frozen for more than two years (Scientific American, December 2009, page 71). According to the 2007 report by the Intergovernmental Panel on Climate Change (page 342), this applies to about 24 percent of the land area of the Northern Hemisphere. The depth of this permafrost layer is anywhere from several feet to 2,000 feet. Much of this land contains large amounts of biomass from extensive bogs and tundra laid down over tens of thousands of years and "locked up" in the frozen ground.
Now, let's look at methane. Yes, it is one of those dreaded greenhouse gases (GHGs) we hear so much about. This particular GHG, the methane molecule, contains one carbon atom and four hydrogen atoms bound together. When the connections between these atoms bend and stretch a little, relative to each other, which it is continuously doing all of the time, the molecule is perfectly tuned to absorb infrared radiation, which it does to a powerful extent.
All atoms bound together in all of the different gas molecules in the atmosphere do the same thing. They move back and forth, up and down, rapidly, relative to one another, but most do not absorb infrared energy. They are transparent. But this particular gas, and the other GHGs, is different. Methane is more than 20 times as effective as carbon dioxide (another GHG) in absorbing infrared energy. In this way radiation that would normally be lost to space is trapped in our atmosphere where it is slowly transferred to the land and to the oceans.
The graph below (derived from one reported by NOAA) shows the changes of methane concentration in our atmosphere over the past 400,000-plus years. Now let's just take a minute or so to see what this graph is telling us. The time axis along the bottom shows us that long period of time for which data exists and which was obtained from ice cores in both Greenland and Antarctica. The oldest time is to the left with today on the far right.
The vertical axis on the left side shows the concentration of methane over that period of time. The units of concentration are in parts per billion (ppb). We can see that over that long span of time the concentrations rose to about 800 ppb, during the warm interglacials such as the one we are in now, and then dropped as low as about 300 ppb when the ice sheets and glaciers were at a maximum. Four glacial cycles can be seen. On the far right, we can see the "Current" level of methane, marked by the circle, which is almost 1,800 ppb. The level today is more than twice the level ever seen in the historical record available to us.
Where does all this methane come from? The answer really is many sources. Much of the world's hundreds of millions of livestock such as sheep, goats, camels, cattle, buffalo and horses have a four-chambered stomach. In one of those chambers, called the rumen, anaerobic bacteria in the absence of oxygen break down food (grasses and other plant and cellulosic materials), and in the process generate methane; lots of it according to an EPA report, "Policy Options for Stabilizing Global Climate" (1990). We are talking about many tens of millions of tons of methane released annually from this source alone.
Methane is also released during energy production and drilling, as well as transport, associated with thousands of miles of pipelines. Methane is the primary component of this natural gas and is a fuel used for heating and many industrial processes. Bogs, swamps and rotting vegetation from harvesting of tropical forests also contribute to the total and it is also commonly called swamp gas.
So now let's talk about this convergence of permafrost and methane issue. The fact is that the permafrost is beginning to melt. The Arctic has taken the brunt of global warming in recent decades and now averages 2.2 degrees Fahrenheit higher than a century ago. More than one-third of permafrost in the Arctic regions is within 2 to 3 degrees Fahrenheit of melting as stated in the December 2009 review in Scientific American.
Bore holes have been drilled into the permafrost all over the Arctic, first by Russian scientists and then later by scientists from other countries. The bore holes are fitted with thermal sensors that capture temperature changes with time. The results are clear. There is a steady increase in temperature over the years down to depths of as much as 65 feet. As mentioned earlier, there is an enormous amount of organic matter frozen in this layer. As it begins to melt, anaerobic decomposition occurs and methane is released.
There are some very telling videos on YouTube showing what happens when scientists poke holes in the ice over Arctic lakes, allowing the trapped gas to escape from under the ice. In one of these, the scientist lights a match and watches as a flame 6 to 12 feet tall erupts from the ice hole. The methane that escapes from the thawed pond in summer, and is not easily observed, collects under the ice in winter allowing for scientific study and measurement.
But the methane story does not end here. There is another big potential source of methane and that is in "methane hydrates." There are vast quantities of this gas trapped in ice cages thousands of feet deep, and below the ocean bottoms, where it is held in place by cold temperatures and extreme pressures. Russian scientists have estimated that more than a trillion tons of this gas lies below the Siberian shelf alone under the ocean. In Norway, surveys have recently found big streams of methane gas bubbles seeping from the ocean bottom. Across the Arctic much of this trapped methane would also be vulnerable to a warming ocean and thawing permafrost.
And so the studies continue. Many scientists, from many different disciplines and many countries, are all working towards an understanding of global warming and the factors that could cause large and rapid changes in our climate as we know it.
The scientific career of Raymond N. Johnson, Ph.D., spanned 30 years in research and development as an organic/analytical chemist; he is currently founder and director of the Institute of Climate Studies USA (www.ICSUSA.org). Climate Science is published the first Sunday of every month.
December 2009 - Permafrost and methane - a chilling story