The Summary
- This was the Arctic’s second-hottest year on record, according to a new NOAA report.
- The tundra has become a source of emissions, rather than a carbon sink, the authors said.
- The Arctic is heating up far faster than places at lower altitudes as melting ice reflects less radiation back to space.
The Arctic just experienced its second-hottest year on record. And concerningly, the region’s tundra has transitioned from being a sink for carbon to a source of emissions as permafrost melts to release methane.
That will only amplify the amount of heat-trapping gases that enter the atmosphere, paving the way for further warming.
The findings, shared Tuesday in the National Oceanic and Atmospheric Administration’s Arctic report card, show how climate change is scrambling ecosystems and shape-shifting the landscape in the part of the planet where global warming is most intense.
Considered a bellwether region for the effects of climate change, the Arctic is heating up far faster than places at lower altitudes — two to four times as quickly, depending on the baselines scientists use for comparison and which geography they include in assessments. The last nine years in the Arctic have all had the highest average temperatures recorded since 1900.
That dynamic is the result of a phenomenon called Arctic amplification. As the Arctic loses snow cover and sea ice, more dark-colored ocean water and rock emerge. Those dark surfaces reflect less radiation back to space, absorbing heat, instead. In addition, patterns of circulation in the oceans and the atmosphere are increasingly transporting heat toward the Earth’s poles.
Together, that means the Arctic is a fundamentally different place from what it was just 10 years ago, said the lead editor of the new NOAA report, Twila Moon, deputy lead scientist and science communication liaison at the National Snow and Ice Data Center.
“The Arctic is in sort of a new regime, not a new normal, of course, but it’s decidedly different than it was even just a couple of decades ago,” she said.
Overall, the Arctic is becoming a greener landscape with more extreme precipitation and less snow and ice, according to the report. The effects of that transformation are increasingly apparent closer to American homes, as fires in the Arctic send smoke to populated areas and as melting ice raises sea levels, scientists said.
“These issues are not not just staying in the Arctic, right — they’re impacting all of us,” said Brendan Rogers, an associate scientist at Woodwell Climate Research Center, in Woods Hole, Massachusetts, who studies permafrost and contributed to the report.
This year’s report includes a detailed accounting of how the carbon cycle is changing in the Arctic. Scientists have been closely watching what happens when permafrost melts, releasing potent greenhouse gases as it thaws and decomposes.
“The permafrost region contains about twice as much carbon as is in the atmosphere now and about three times as much carbon as in the aboveground biomass of all the world’s forests, so it’s a lot of carbon that’s at stake here,” Rogers said.
He added that permafrost regions have “been carbon sinks for millennia, on average, largely because of cold temperatures and frozen soils.” A carbon sink, by definition, absorbs and captures more carbon dioxide than it releases. But now, Rogers said, such regions have instead become a source of greenhouse gas emissions as they thaw and release that carbon and methane into the atmosphere.
Wildfires are also contributing to Arctic emissions. Last year, wildfires burned more than twice as much area in the region as in any previous year — exceeding the emissions from Canada’s economic activity.
“It’s roughly three times the amount from all other Canadian sectors,” Rogers said of Canada’s total wildfire emissions. “It’s higher than in any other country’s annual emissions except for China, the U.S., India and Russia.”
Wildfire forced the evacuation of Yellowknife, the capital of Canada’s Northwest Territories, last year. About 19,000 people had to flee the city, which is in an area with discontinuous permafrost.
Temperature records are organized by Arctic water year, so the most recent one ran from October 2023 through September 2024. Every September, scientists measure the extent of Arctic sea ice at its seasonal minimum.
This year, sea ice was the sixth-lowest in the 45 years since satellites began measuring; sea ice extents have decreased about 50% since the 1980s. Meanwhile, the Arctic tundra was the second-greenest since records began in 2000, indicating that more shrubs had taken root and expanded into new terrain.
Measurements of Arctic permafrost, which are taken from boreholes drilled below the surface, had higher average temperatures than in all but one previous year.
“There are many metrics in which we’re just seeing this consistently extreme and near extreme,” Moon said.
