Arctic Tundra Turns from Carbon Sink to Source, NOAA’s 2024 Report Card Warns

The Arctic tundra, once a carbon sink for millennia, is now releasing significant amounts of carbon dioxide (CO2) and methane (CH4) into the atmosphere, according to NOAA’s 2024 Arctic Report Card. This shift is largely attributed to thawing permafrost and intensifying wildfires, both driven by rising surface air temperatures and increasing greenhouse gas accumulation. 

Permafrost thaw releases vast stores of ancient carbon, broken down by microbial activity into greenhouse gases. This process is compounded by disturbances such as wildfires, which contribute to sudden bursts of CO2 and CH4. In 2024, permafrost temperatures reached record highs at nine of 20 long-term monitoring sites surveyed in Alaska. Over the past four decades, permafrost in Northern Alaska (North Slope) has warmed by 0.3 to 0.7°C per decade, while interior Alaska has experienced smaller but notable increases of 0.02 to 0.3°C per decade. 

Wildfire activity has surged, with burned areas over the past two decades (2004–2023) 28% larger than the 1981–2000 average and 62% higher than the 1971–1990 average. This year, wildfire emissions north of the Arctic Circle were the second highest on record, releasing substantial greenhouse gases and amplifying the warming feedback loop. 

While the Arctic as a whole was carbon neutral from 2001 to 2020, the tundra region has now shifted to a net carbon dioxide source, emitting methane as well. In contrast, the boreal forest continues to act as a carbon sink, absorbing and storing atmospheric carbon. The report highlights that vegetation regrowth following wildfires can re-sequester carbon over decades, but the increasing frequency and severity of fires, combined with long-term ground thaw, are driving sustained carbon emissions across large areas. 

These findings underscore the urgent need for climate action to address the accelerating feedback mechanisms reshaping the Arctic’s carbon balance. The Arctic tundra’s transition to a net carbon source carries profound regional and global consequences, accelerating rapid Arctic ice melt, influencing both global atmospheric and ocean temperatures, weather patterns, and precipitation levels. These changes can escalate food and water insecurity and heighten the risk of infectious diseases by disrupting ecosystems and human livelihoods. Addressing this crisis requires collective action; governments must prioritize the transition away from fossil fuels and invest in renewable energy infrastructure, while private organizations and individuals should adopt more sustainable, resource-efficient lifestyles. Proactive measures to reduce greenhouse gas emissions and adapt to rapid climate shifts are essential for safeguarding human health and well-being, both now and for future generations.

Feature image: Terrestrial ecosystem CO2 fluxes, including direct fire emissions, are depicted for the northern permafrost region (2002–2020 average), with pink and red areas indicating CO2 sources and blue areas representing CO2 sinks. (Data from Virkkala et al., 2024). Credit: NOAA. 

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