The Arctic tundra was a carbon sink. Now it contributes to global emissions

The Arctic tundra is now emitting more carbon dioxide than it absorbs, according to the latest Arctic Report Card released by the US National Oceanic and Atmospheric Administration (NOAA). The annual assessment reveals that warming temperatures and increased wildfires have shifted the Arctic from a carbon sink to a net source of greenhouse gas emissions.

"Our observations now show that the Arctic tundra, which is experiencing warming and increased wildfire activity, now emits more carbon than it stores, which will worsen the impacts of climate change," NOAA Administrator Rick Spinrad stated.

The report highlights that the period from October 2023 to September 2024 was the second-warmest for the Arctic region since 1900, emphasizing numerous changes affecting both ecosystems and human communities.

The thawing permafrost is a significant factor in this shift. When permafrost thaws, carbon that has been stored in the frozen soil is decomposed by microbes, leading to the release of carbon dioxide and methane into the atmosphere. The melting permafrost also activates microbes in the soil, leading to the decomposition of trapped carbon into greenhouse gases, including carbon dioxide and methane.

Wildfires have become more frequent and intense in the Arctic due to climate change. According to NOAA's report, wildfires in the Arctic have increased in burned area, intensity, and associated carbon emissions, playing a central role in the tundra's transition to a net carbon source. "By burning vegetation and soil organic matter, tundra fires release carbon dioxide into the atmosphere and add pulses of greenhouse gases while accelerating the long-term thawing of permafrost," stated the report.

Brendan Rogers, a scientist at the Woodwell Climate Research Center who contributed to the Arctic Report Card, said emissions from the region are likely to continue as the climate warms. "The more we can do to lower the overall temperature changes globally, the better we're going to be able to deal with permafrost emissions," Rogers said. He emphasized that there is still time to slow the thaw.

Climate scientists express deep concern over the implications of this shift. Brenda Ekwurzel, a climate scientist at the Union of Concerned Scientists, called it "an alarming warning sign." "These combined changes are contributing to worsening wildfires and thawing permafrost to an extent so historic that it caused the Arctic to be a net carbon source after millennia serving as a net carbon storage region," she said.

Wildfires have been particularly devastating. In recent decades, tundra fires have continued to increase, with 2023 marking a record year for wildfire emissions, particularly in permafrost areas. "The fires emitted nearly 400 million tons of carbon—more than two-and-a-half times the emissions from all other sectors in Canada combined," according to Brendan Rogers.

The warming Arctic has dual effects, adversely impacting soil, ice, plants, animals, and communities that rely on them, with consequences extending far beyond the region. The warming in the Arctic directly influences global sea-level rise, weather patterns, and wildlife migrations, all driven primarily by burning fossil fuels.

Permafrost in the Arctic has stored enormous amounts of carbon dioxide for millennia, holding more than twice as much as is currently in the atmosphere, contributing to the Arctic's role as a carbon sink. As permafrost thaws, its carbon repositories decompose, releasing carbon into the atmosphere. This creates a continuous feedback loop that could become a potentially massive source of greenhouse gas emissions contributing to climate change.

Wildlife in the Arctic is also being impacted by these changes. Summer heat is disrupting the movements and survival of tundra caribou. One main reason for the decline in tundra caribou is that they are often eating less, and changes to winter snow and ice conditions are also affecting them. "Hotter summers have led to more mosquitoes in the Arctic," the report noted. "The mosquitoes can become so annoying that the caribou focus on avoiding them at the expense of eating."

Sue Natali, a scientist at the Woodwell Climate Research Center in Massachusetts, underscored the importance of reducing greenhouse gas emissions and continuing climate change research. "This is not an issue of what party you support. This is something that impacts everyone," she stated.

This article was written in collaboration with generative AI company Alchemiq