Permafrost Thawing Determined by Water in Soil: New Discovery for Climate Models

First Posted: Jul 29, 2013 09:28 AM EDT

In the far northern reaches of our planet, permafrost keeps the Arctic tundra hard and frozen almost year-round. This icy layer gives the ground stability, keeping it from slumping downward and sinking. Yet this permafrost also serves another purpose; it traps greenhouses gases such as carbon dioxide and methane. Now, scientists have found that thawing permafrost is releasing substantial amounts of carbon dioxide into the atmosphere and that water content in the soil is crucial when it comes to predicting this thawing.

Thawing permafrost isn't a new finding. Scientists have been well aware of the effects associated with the phenomenon for years. In fact, research in Greenland has found that permafrost thaws at a rate of about 1 centimeter per year. Yet actually predicting the rate of this thawing is another matter entirely. In addition, the rate at which carbon dioxide is released from permafrost is also poorly documented and is one of the most important uncertainties of current climate models.

In order to examine this phenomenon a bit closer, researchers carried out measurements over a 12-year period. They also analyzed water content in the soil that they studied. In the end, they found that future water content in the soil will be a decisive factor when it comes to predicting the effects of permafrost thawing.

"From a climate change perspective, it makes a huge difference whether it takes 10 or 100 years to release, e.g., half the permafrost carbon pool," said Bo Elberling, one of the researchers, in a news release. "We have demonstrated that the supply of oxygen in connection with drainage or drying is essential for a rapid release of carbon dioxide into the atmosphere."

If permafrost remains saturated after thawing, the carbon decomposition rate will be very slow. In fact, the release of carbon dioxide will take place over several hundred years in addition to methane that is being produced in water logged conditions. This, in particular, has important implications when it comes to developing climate models.

The new study is important to climate scientists currently developing models that reveal exactly how much carbon will be released into our atmosphere in the future. It reveals exactly how water content can play a huge role in the release of this carbon, either helping to speed up or slow down the process.

The findings are published in the journal Nature Climate Change.

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