The frozen ground just below the Earth’s surface might hold a hidden danger for the planet’s climate. Permafrost teems with microbes that could be able to accelerate global warming under the right conditions.
Scientists have long known that several mechanisms can contribute to global warming, including carbon dioxide emissions from engines and power plants. The melting of the permafrost in northern latitudes is another source of so-called greenhouse gases. What wasn’t so clear before was the mechanism that released carbon dioxide and methane from the frozen tundra.
Researchers at Florida State University conducted a study of how the permafrost works, and found a simple mechanism involving bacteria, that could contribute in a substantial way to climate change.
What happens depends on organic material being available. Availability depends on whether the soil remains frozen or not. In the Arctic, that permafrost is thawing, making more organic material available to those microbes.
Environmental scientist Jeff Canton, of Florida State University, described the process. Frozen soil starts to thaw. The layer of soil collapses into what used to permafrost and becomes saturated with water. Organic matter in the water is now available to be broken down by anaerobic (able to grow in the absence of oxygen) bacteria to produce carbon dioxide and methane, which can lead to global warming.
Using a sample of Arctic permafrost, the international research team studied soil composition, focusing on what would change the ratio of methane to carbon dioxide produced by bacteria present below the surface.
The amount of carbon dioxide is greater, at first, than the amount of methane. Over time, the organic matter changes in composition, in a way that increases methane production much more than carbon dioxide production. Production of both gases increases, but the ratio changes from 10:1 to 1:1, said Dr. Chanton.
The latest study is part of a world-wide collaborative effort involving scientists from Australia, Europe, and North America. The methane in the soil gets released as new plant species, sphagnum moss then sedges start to grow. Methane is 33 times more powerful a greenhouse gas than is carbon dioxide. As the world gets warmer, additional methane would just add to the problem.
Suzanne Hodgkins, doctoral student at Florida State University and lead author of the study, said that we have known about the thawing permafrost. The new study shows that changes in plants growing in the far north could lead to far more greenhouse gases being released into the atmosphere.
The paper was published in Proceedings of the National Academy of Sciences.
Permafrost covers approximately 24 percent of the exposed land in the northern hemisphere, with most being in Siberia, northern Canada, and Alaska. Some alpine permafrost exists further south in the mountains.
Another study on the connection between greenhouse gases and the landscape indicated that deserts could trap more carbon dioxide than previously thought. That study was published April 6 in the online science journal Nature Climate Change.
Now that scientists know how changes in tundra permafrost can release greenhouse gases, the challenge remains to actually do something about it. Knowing that global warming could be accelerated by microbes under the tundra adds another mechanism of climate change to cope with.
By Chester Davis