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The Arctic tundra, a frozen, treeless biome, has historically been a vital carbon sink, absorbing vast amounts of carbon dioxide (CO?) and other greenhouse gases (GHGs). However, recent findings suggest that, for the first time in millennia, this ecosystem is emitting more carbon than it absorbs, a change that could have significant global consequences. This alarming shift was highlighted in the 2024 Arctic Report Card published by the National Oceanic and Atmospheric Administration (NOAA).

The Arctic Tundra’s Role as a Carbon Sink

The Arctic tundra plays a crucial role in regulating the Earth's climate. In typical ecosystems, plants absorb CO? through photosynthesis, and when they die, carbon is either consumed by decomposers or released back into the atmosphere. In contrast, the tundra’s cold environment significantly slows the decomposition process, trapping organic carbon in permafrost—the permanently frozen ground that underpins much of the region.

Over thousands of years, this accumulation of organic matter has resulted in the Arctic storing an estimated 1.6 trillion metric tonnes of carbon. This figure is roughly double the amount of carbon in the entire atmosphere. As such, the tundra has served as a critical carbon sink, helping to mitigate global warming by trapping vast quantities of CO?.

Shifting Dynamics: Emission of Greenhouse Gases

Recent reports indicate a dramatic shift in the Arctic tundra’s role in the carbon cycle. Rising temperatures and increasing wildfire activity have disrupted the tundra’s balance, leading it to transition from a carbon sink to a carbon source.

Impact of Rising Temperatures

The Arctic region is warming at a rate approximately four times faster than the global average. In 2024, Arctic surface air temperatures were recorded as the second-warmest on record since 1900. This rapid warming is causing permafrost to thaw, which in turn activates microbes that break down trapped organic material. As this decomposition accelerates, carbon in the form of CO? and methane (CH?)—a more potent greenhouse gas—are released into the atmosphere.

The experts, explained the process by comparing thawing permafrost to meat left out of the freezer. Similarly, thawing permafrost accelerates the breakdown of trapped carbon.

The Role of Wildfires

In addition to warming temperatures, the Arctic has experienced a surge in wildfires in recent years. 2024 marked the second-highest wildfire season on record in the region, releasing significant amounts of GHGs into the atmosphere. Wildfires exacerbate the thawing of permafrost, creating a feedback loop where increased carbon emissions contribute further to warming, which, in turn, leads to more emissions.

Between 2001 and 2020, these combined factors caused the Arctic tundra to release more carbon than it absorbed, likely for the first time in millennia.

The Global Consequences of Emission

The transition of the Arctic tundra from a carbon sink to a carbon source is alarming, as it represents a significant amplification of global climate change. The release of additional CO? and CH? into the atmosphere further accelerates the greenhouse effect, leading to higher global temperatures. This warming is already having visible consequences around the world, from extreme weather events to rising sea levels.

If the Arctic tundra continues to emit more carbon than it absorbs, it could significantly exacerbate the climate crisis. The report underscores the urgency of addressing global emissions, as reducing greenhouse gases remains the most effective way to prevent further destabilization of this sensitive ecosystem.

Mitigating the Impact: The Path Forward

Despite the alarming trends, the Arctic Report Card suggests that it is still possible to reverse this process. By reducing global GHG emissions, it may be possible to slow the thawing of permafrost and allow the Arctic tundra to regain its role as a carbon sink. Scientists emphasize that mitigating climate change on a global scale is essential to prevent further emissions from the Arctic ecosystem.

Scientists, stressed the importance of emission reductions, stating, “With lower levels of climate change, you get lower levels of emissions from permafrost… That should motivate us all to work towards more aggressive emissions reductions.”

However, current trends suggest that achieving this goal may be challenging. A recent report from the Global Carbon Project indicates that fossil fuel emissions are likely to rise in 2024, with total CO? emissions projected to reach 41.6 billion tonnes, up from 40.6 billion tonnes in 2023.