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Abrupt permafrost thaw releases more CO2 than expected

Recent research has shed light on a pressing environmental issue: the impact of abrupt permafrost thaw, known as thermokarst, on carbon dioxide (CO2) emissions from soil.

A significant finding from the study is that soil CO2 emissions are more sensitive to climate warming in areas where permafrost has collapsed than in regions where it remains intact.

Exploring the depths of permafrost carbon

Permafrost regions, particularly those at high latitudes and altitudes, store about half of all below-ground organic carbon.

These areas are crucial in maintaining the balance of our climate system. However, with rising global temperatures, permafrost is thawing rapidly.

Thermokarst, the sudden collapse of permafrost due to melting ice within the soil, affects roughly 20% of the northern permafrost region.

This type of thaw can drastically alter the land’s morphology and the properties of the soil, potentially leading to significant changes in ecosystem carbon cycling.

Climate warming and soil CO2 flux

Both thermokarst and non-thermokarst areas are experiencing ongoing warming, yet the effects on soil CO2 flux in these regions are markedly different.

This discrepancy has prompted a group of researchers led by Professor YANG Yuanhe from the Institute of Botany of the Chinese Academy of Sciences to delve deeper into the phenomenon.

Through field and laboratory studies, the team discovered that the warming-induced increase in soil CO2 release was approximately 5.5 times higher in thermokarst areas compared to adjacent non-thermokarst regions.

The mechanisms of soil CO2 release

The team employed multiple scientific techniques, including soil physicochemical analyses, solid-state 13C nuclear magnetic resonance, and metagenomic sequencing. The researchers identified over 30 potential factors influencing the warming effects on soil carbon release.

They found that the greater response in thermokarst areas is primarily due to the lower quality of soil substrates and a higher abundance of microbial genes related to the decomposition of organic carbon.

Further analysis involved incubating soils from six additional thermokarst-affected sites along a 550-km permafrost transect.

Results from these experiments showed that thermokarst formation significantly increases the temperature sensitivity of soil carbon release, suggesting a stronger response of soil CO2 to warming in these landscapes.

Broader study implications

Professor YANG highlighted the broader significance of these findings: “As a preliminary exploration of its global importance, extrapolating the warming response of soil CO2 flux to all upland thermokarst regions in the Northern Hemisphere, there could be an additional 0.4 Pg C year-1 of soil carbon release.”

This amount represents about a quarter of the projected permafrost soil carbon losses by the end of the 21st century.

Consequently, these insights are vital for accurately projecting future trajectories of permafrost carbon-climate feedback.

Understanding how thermokarst influences CO2 emissions can help scientists and policymakers develop more effective strategies to address the challenges posed by climate change.

Permafrost dynamics and global warming

The study provides compelling evidence that soil CO2 loss becomes stronger upon abrupt permafrost thaw. This means that thermokarst areas are significantly more vulnerable to climate-induced increases in soil CO2 emissions than their non-collapsed counterparts.

The research is critical for enhancing our understanding of permafrost dynamics and their impact on global warming, paving the way for more informed environmental decision-making in the face of climate change.

Impacts of permafrost thaw and CO2 release

Permafrost thaw can lead to significant changes in an ecosystem, affecting the plants and animals adapted to permafrost environments. In addition, the infrastructure built on permafrost, like roads and buildings, faces increased risk of damage as the once-stable ground becomes unstable.

Moreover, permafrost contains vast amounts of organic carbon that have been frozen for millennia. When permafrost thaws, this carbon is exposed to bacteria and fungi that convert it into carbon dioxide and methane, potent greenhouse gases that further contribute to global warming.

This creates a feedback loop where warming leads to more thawing, which leads to more emissions, which leads to further warming.

The process and impacts of permafrost thaw are being intensely studied as they present critical challenges not only to local communities but also to global efforts in managing climate change impacts and maintaining sustainability.

The study is published in the journal Nature Geoscience.


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