The frigid Arctic tundra has soaked up carbon dioxide from the atmosphere for millennia, an essential balancer for our planet’s climate. Now, as global temperatures rise, it appears to be emitting more heat-trapping gases than it is absorbing. The switch threatens to exacerbate warming and shows that climate change is not always a gradual process, but can accelerate with sudden action.
The National Oceanic and Atmospheric Administration publishes its annual Arctic Report Card This week, pooling research from Planet North. As the warmest year on record comes to an end, researchers have found that the Arctic is warming four times faster than the global rate, with adverse consequences for the soil, ice, plants and animals that live there. Then those plants will eat the communities that depend on them and everyone else on Earth.
It’s another sign of what scientists predict will be the consequences of insufficiently reducing fossil fuel pollution, NOAA Administrator Rick Spinrad said in a statement.
about 4 million people Lives north of the Arctic Circle. It is an important geopolitical choke point that has become more accessible to shipping as sea ice recedes, creating regional tensions between the countries. Race for minerals and oil.
The Arctic is also important for global climate because it drives oceanic and atmospheric currents at low latitudes. It’s a region where scientists can observe discrete changes as average temperatures rise, such as when reflective sea ice opens up, sunlight-absorbing oceans, or when it rains instead of snowing.
Now scientists can add the arctic tundra to that list.
In most ecosystems, plants absorb carbon dioxide from the atmosphere. Those plants grow, die, or are eaten by animals that also grow and die. The carbon in their carcasses — lignin, cellulose, fatty acids, proteins and more — feeds microorganisms that break down larger molecules and release carbon dioxide back into the air, completing the carbon cycle.
Tundra, a frozen treeless arctic biome with long dark winters and short summers, alters the balance of this cycle. Although it doesn’t have the dense, fast-growing biomass of a tropical rainforest, its vegetation almost respires. One billion metric tons of carbon dioxide each yearAbout one-fifth of the total annual production of mankind. Beneath the tundra, permafrost, a layer of soil that remains frozen year-round, keeps microbes at bay that would normally decompose plants. The net result is that Arctic soils store enormous amounts of carbon, 1.6 trillion metric tons across the entire region. This is almost double the amount of carbon in the atmosphere.
However, as average global temperatures rise, permafrost isn’t as “perma” anymore, and once-dormant microbes begin to wake up hungry, chewing up organic matter in the soil. This leads to higher emissions of carbon dioxide as well as methane, a more potent greenhouse gas. Over the years, melting permafrost has shifted the carbon balance to such an extent that The Arctic is absorbing less and emitting more (Sidenote: ice “melts,” permafrost “melts”). This year, nine of the 20 permafrost monitoring sites reported record-high temperatures
However, this is not always a straightforward process. “Warming temperatures tend to increase carbon dioxide uptake in the summer,” he said Brendan RodgersA scientist at the Woodwell Climate Research Center who contributed to the Arctic Report Card, during a press conference. “But they increase net carbon dioxide emissions in soil microbes in fall, winter and spring.”
But another factor turned Arctic tundra from carbon sink to carbon source: wildfires. Notably, wildfires have occasionally ignited in the Arctic in the past, but in recent years, their frequency and intensity have increased. Looking at the years between 2001 and 2020, the researchers found that fires are a key source of greenhouse gases and represent an urgent perennial concern for Arctic residents. Last year was the Arctic’s worst wildfire season on record, and this year was the second largest year for wildfire emissions.
Fires can then create a feedback loop that leads to further thawing of permafrost, burning more of the landscape.
It is possible that the tundra could shift in the other direction, toward a net sink, if global temperatures fall.
Rogers noted that there is year-to-year variability in how much carbon the region absorbs, indicating that there are short-term drivers at work. But the results highlight that humanity cannot take traditional carbon-absorbing biomes for granted. It’s not just greenhouse gas emissions from burning fossil fuels that are driving warming, but also the loss of critical natural systems used to offset heat-trapping gases. And its effects are already beginning to show.
“We’re now seeing the impacts together in real time in the Arctic, and that’s a call to action,” Spinrad said.
