Study Reveals How Thawing Permafrost Increased Carbon Dioxide Levels After the Last Ice Age

Recent research shows that thawing permafrost has played a bigger role in rising carbon dioxide levels than we previously thought. Scientists from the University of Gothenburg discovered that a significant amount of CO₂ released into the atmosphere after the last ice age came from melting permafrost.

Climate shifts between ice ages and warmer periods typically influence CO₂ levels. During ice ages, CO₂ drops, only to increase again in warmer interglacial periods, usually by about 100 parts per million (ppm). Past theories suggested that this rise was mainly due to changes in ocean temperatures, which affect carbon storage. However, new findings indicate that thawing permafrost has also contributed heavily to this increase. Researchers note that thawing land north of the Tropic of Cancer may have contributed to almost half of the rise in atmospheric CO₂ during that time, according to the study published in Science Advances.

Amelie Lindgren, a researcher involved in the study, explains that many ecosystems in these regions released stored carbon when temperatures began to rise post-ice age. During the Ice Age, plants and organic materials froze into the ground, accumulating and trapping carbon. This carbon-rich soil can be found in various regions, including Europe, Asia, and parts of North America, and has remained intact longer due to the cold climate slowing down decomposition.

The team analyzed 21,000 years of pollen samples and climate data to piece together the vegetation history. This snapshot method allows scientists to estimate how much carbon was stored in the soil at various points in time. Around 21,000 years ago, the Earth was colder, with extensive ice coverage. As the climate warmed between 17,000 and 11,000 years ago, much of this permafrost began to thaw, releasing CO₂.

• At the peak of the ice age, CO₂ levels were about 180 ppm.
• By 11,000 years ago, during a warmer period, levels had risen to 270 ppm.

While this natural fluctuation is normal, the current situation is different. Over the past 250 years, human activities have changed the carbon cycle dramatically. The burning of fossil fuels has increased atmospheric CO₂ levels from 280 ppm to around 420 ppm today. This rapid rise poses a serious challenge. Lindgren mentions that, unlike in the past when peatlands helped absorb carbon, today’s rising sea levels limit our options for carbon storage.

The shift towards warmer temperatures has already started affecting permafrost and could lead to further emissions. Understanding the role of permafrost today is crucial as we face the complexities of climate change.

For more details, you can check the research by Amelie Lindgren and colleagues on the Science Advances website.

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