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Arctic Tundra: From Carbon Sink to Carbon Source
Context:
The Arctic tundra, traditionally a carbon sink that stores vast amounts of carbon, has now become a source of greenhouse gas emissions due to the combination of rising temperatures and increased wildfires.
Key Highlights:
- This alarming transformation is highlighted in the 2024 Arctic Report Card by the National Oceanic and Atmospheric Administration (NOAA), showing that the Arctic is warming at four times the global rate.
- The Arctic Report Card suggests that it may still be possible to reverse this trend, but only through aggressive reductions in global greenhouse gas emissions. Lower levels of climate change would slow the thawing of permafrost, limiting the amount of carbon released.
- However, this is challenging as global emissions continue to rise, with projections showing a slight increase in CO2 emissions in 2024 compared to the previous year.
- The Global Carbon Project reports that CO2 emissions from burning fossil fuels and land-use changes like deforestation are set to increase.
The Role of Arctic Tundra in Carbon Storage:
- The Arctic tundra has historically been a carbon sink, storing over 1.6 trillion metric tonnes of carbon in its permafrost (soil that remains frozen for at least two years).
- This carbon comes from organic matter, including plants and animals, that decomposes slowly due to the cold climate.
- The cold prevents microbes from breaking down this matter, thus trapping carbon dioxide (CO2) and methane (CH4) — potent greenhouse gases — in the ground.
- This carbon storage has been critical in regulating global atmospheric CO2 levels.
Why the Arctic Tundra Is Emitting More Carbon?
- The Arctic is experiencing unprecedented warming, with 2024 temperatures being the second warmest on record.
- This warming has led to thawing permafrost, which in turn has activated microbes that start to break down the trapped organic matter, releasing CO2 and methane into the atmosphere.
- Wildfires have also become more frequent and intense in the Arctic, further contributing to carbon emissions.
- In 2024, the Arctic saw the second-largest wildfire season on record.
- Wildfire smoke releases carbon into the air while also accelerating the thawing of permafrost, creating a feedback loop where thawing leads to more carbon release, which in turn accelerates climate change.
The feedback loop caused by thawing permafrost and wildfires is alarming because it exacerbates the global warming crisis. Between 2001 and 2020, the Arctic tundra began to emit more carbon than it absorbed for possibly the first time in millennia. This shift from a carbon sink to a carbon source has the potential to accelerate climate change, adding to the atmospheric load of greenhouse gases.
Implications:
- Climate Change: The transition of the Arctic tundra from a carbon sink to a carbon source is a significant concern for climate scientists. It highlights the urgent need to reduce fossil fuel pollution and implement effective mitigation strategies.
- Ecosystem Impact: The changes in the Arctic are forcing plants, wildlife, and Indigenous communities to rapidly adapt to a warmer, wetter, and less predictable environment. Declines in caribou herds and other wildlife are already being observed.
- Global Impact: The increased carbon emissions from the Arctic contribute to the overall rise in atmospheric greenhouse gases, further driving global climate change.
