Permafrost, the thick layer of soil that remains frozen throughout the year, currently holds a large amount of carbon. If the permafrost thaws, it will release the stored carbon, which could contribute to further warming. This is not new news.
What is new is the idea that high latitude areas will become a carbon source rather than a carbon sink. The 2007 assessment report from the Intergovernmental Panel on Climate Change suggested that the thawed permafrost would allow for greater vegetation in polar regions, leading to carbon uptake. But a recent study published in the Proceedings of the National Academy of Sciences contradicts that assertion.
The authors of that study–Charles Koven, of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a team of scientists from France, Canada, and the United Kingdom–used a model that took into account how carbon behaves in different layers of the ground.
But unlike earlier models, the new model includes detailed processes of how carbon accumulates in high-latitude soil over millennia, and how it’s released as permafrost thaws. Because it includes these processes, the model begins with much more carbon in the soil than previous models. It also better represents the carbon’s vulnerability to decomposition as the soil warms.
New models lead to updated forecasts on what is likely to happen to Earth’s climate. But this isn’t the final word. Even the latest and greatest models can be refined to make ever-better forecasts of the future.
Koven adds that there are large uncertainties in the model that need to be addressed, such as the role of nitrogen feedbacks, which affect plant growth. And he says that more research is needed to better understand the processes that cause carbon to be released in permanently frozen, seasonally frozen, and thawed soil layers.
The quest to forecast the future continues.
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