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For the 11th year in a row, the Arctic warmed more drastically than the rest of the world, a change that continues to bring cascading consequences to Arctic systems, wildlife, and residents.
The authors of this year’s Arctic Report Card said the consistently extreme climate observations in the Arctic indicate a “new regime”—a rapidly and drastically changing climate much different from that seen in the 20th century. The disruptions spurred by climate change are pushing the Arctic into “uncharted territory,” the report authors wrote.
NOAA releases the Arctic Report Card annually to give an update on the region’s climate and environmental systems. The report was released on 10 December at AGU’s Annual Meeting 2024 in Washington, D.C.
“A new regime is not the same as a new normal,” said Twila Moon, an ice scientist at the National Snow and Ice Data Center and an author of the report.“We’re going to continue to see rapid and large changes in the Arctic…but year after year, we’re seeing extreme or close to extreme events.”
Slushy Seas
One of the first indicators of global climate change is sea ice, said Walter Meier, a sea ice scientist at the National Snow and Ice Data Center and author of the report. In 2024, the September monthly average sea ice extent (the lowest sea ice month of the year) was the sixth lowest on record. Sea ice in the Hudson Bay began to recede roughly a month earlier than normal, and thin ice near the North Pole fractured, revealing open water. “It’s gone from a sheet of ice to a slushy, basically,” Meier said.
Less ice allowed for record Arctic ship traffic on the Northern Sea Route, and a Chinese vessel became the first large container ship to complete a voyage in the Arctic.
A figure shows three sea ice measurements: March total extent, September total extent, and the September extent of multiyear ice. All three measurements and their trend lines steadily decline from 1979 to 2024.
Sea ice extent in the lowest (September) and highest (March) sea ice months has declined steadily since 1979. The September multiyear extent refers to the extent of ice that has survived at least one melt season. Credit: NOAA’s Arctic Report Card 2024
The continued decline in sea ice extent is due to warming air and ocean temperatures—Arctic seas this August were about 2°C–4°C (3.6°F–7.2°F) warmer than the 1991–2020 baseline, and air temperatures were the second warmest on record.
“I suspect we may be on the ledge of another tipping point.”
Meier said that though sea ice minimums have been consistently low since about 2007 and steadily decreasing since the 1980s, he expects to see another precipitous drop within the next few years, as thicker, older ice is now exposed to ever-warmer temperatures. “I suspect we may be on the ledge of another tipping point,” he said.
A recent study published in Nature Communications projected that the first ice-free day in the Arctic could occur before 2030.
Sink to Source
Other evidence of the Arctic’s new climate regime is the transition of parts of the region into sources, rather than sinks, of carbon dioxide—reversing the Arctic’s thousands-of-years history of trapping rather than releasing the world’s atmospheric carbon. That flip is primarily due to warming air temperatures, which are thawing permafrost (perennially frozen soil) and releasing greenhouse gases trapped within. Permafrost temperatures in Alaska this year were the second warmest on record and the warmest ever for 9 of the 20 long-term monitoring stations in the state.
A map of the Arctic shows carbon dioxide fluxes. The proportion of locations that are sources of carbon dioxide compared to sinks increases as latitude increases. Dark red indicates areas with emissions from wildfire.
Many locations in the Arctic are now sources, rather than sinks, of carbon dioxide. Credit: NOAA’s Arctic Report Card 2024, Virkkala et al., 2024, https://doi.org/10.3334/ORNLDAAC/2377
Permafrost thaw “could be a major feedback in the Earth system that contributes to climate warming,” said Brendan Rogers, an Arctic scientist at the Woodwell Climate Research Center and an author of the report.
An increase in the frequency and intensity of Arctic wildfires has also played a role in releasing carbon dioxide.
The shift from a sink to a source is “of global concern” because it complicates efforts to rein in emissions, the authors wrote. The findings on permafrost emissions should “provide extra motivation to be more ambitious about meeting climate targets,” Rogers said.
Climate Confusion
Though long-term averages show clear trends in the Arctic as a whole, regions within the Arctic are experiencing different changes at different rates. This year, some portions of the Canadian Arctic experienced much shorter snow seasons, whereas portions of the Eurasian Arctic saw a longer period of snow.
Regional differences make it challenging to plan for certain weather conditions and disrupt the lives of Arctic residents, the report authors wrote.
Populations of migratory caribou in the Arctic have decreased by about 65% since their populations peaked in the 1990s and 2000s as they struggle to adapt to climate changes and human impact. The decline poses challenges for communities that rely on caribou for food. The report authors wrote that the knowledge of Indigenous hunters will be key to understanding caribou dynamics and other Arctic systems as the region warms.
“The best time to have acted really decisively was probably about 40 years ago,” Rogers said. “But the next best time is now.”
—Grace van Deelen (@GVD__), Staff Writer
Citation: van Deelen, G. (2024), Another hot Arctic year indicates a new climate regime, Eos, 105,https://doi.org/10.1029/2024EO240566. Published on 10 December 2024.
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