When including the impact of increased wildfire activity, the Arctic tundra region has shifted from storing carbon in the soil to becoming a carbon dioxide source. NOAA

Foreboding environmental milestones abounded again this year in the Arctic, where experts say dramatic climate shifts are fundamentally altering the ecosystem and how it operates. One recent turning point for the region involves its carbon footprint: Where conditions in the Arctic historically worked to reduce global emissions, they're now actively contributing to them.

That's a major transition that could reap consequences on human, plant and animal life far beyond Earth's northernmost arena, warned a cohort of scientists whose research appears in the National Oceanic and Atmospheric Administration's 2024 Arctic Report Card, published Tuesday. The report is an annual assessment of the polar environment, which in recent years has become a stark alert signal marked by unprecedented and ominous observations all linked to rising temperatures from human-caused climate change.

A focus of the latest Arctic evaluation was the effects of warmer weather and wildfires on the tundra, a far-northern biome that's typically known for extreme cold, little precipitation and a layer of permanently frozen soil, called permafrost, covering the land. Those traits collectively made the Arctic an important carbon sink for millennia, meaning the region essentially helped reduce carbon dioxide emissions worldwide by absorbing more carbon than it emitted into the atmosphere.

That has mainly been due to carbon uptake from plants, which regulate atmospheric levels of the molecule through photosynthesis, and a storage process in the permafrost, which traps carbon dioxide in the ground. But warming air temperatures in the Arctic are breaking down permafrost across the tundra, in some cases, severely. The Arctic report, for example, showed Alaskan permafrost temperatures in 2024 were the second-warmest ever recorded. That causes the soil to heat up and thaw, its carbon repositories decompose along with it.

Research included in NOAA's Arctic report shows carbon once stored in the tundra's permafrost is actually being released into the atmosphere. In parts of the region, it's happening at a rate that outweighs the carbon sink and instead creates a net increase in greenhouse gas emissions — something of particular concern to climate scientists at a time when pollution from fossil fuel production has already reached a record high.

The same fossil fuels overwhelming the atmosphere and prompting ongoing admonition from top weather and climate officials at the United Nations are fueling the emissions in the Arctic, said Rich Spinrad, the administrator of NOAA, in a statement on the new report's findings.

"Our observations now show that the Arctic tundra, which is experiencing warming and increased wildfire, is now emitting more carbon than it stores, which will worsen climate change impacts," Spinrad said. "This is yet one more sign, predicted by scientists, of the consequences of inadequately reducing fossil fuel pollution."

Wildfires in the Arctic have been raging at rates never seen before, and that alone drives up carbon emissions. Researchers suggest 2024 had the second-highest annual volume of wildfire emissions north of the Arctic Circle on record. Coupled with the release of carbon dioxide and methane gas from permafrost stores, they say net emissions could continue to increase in the place that climate change is heating up faster than anywhere else on the planet.

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