Arctic tundra is currently emitting more carbon than it absorbs, causing climate change

The frigid Arctic tundra has been absorbing carbon dioxide from the atmosphere for thousands of years, making it an important balancer of Earth’s climate. Currently, as Earth’s temperature rises, it appears to be releasing more heat-trapping gases than it absorbs. This switch could further amplify warming, showing that climate change is not necessarily a gradual process and can accelerate in sudden steps.

The National Oceanic and Atmospheric Administration this week released its annual Arctic Report Card, a compilation of research in the global north. As perhaps the hottest year on record draws to a close, researchers are discovering that the Arctic region is warming four times faster than the rest of the world, with changes in soil, ice, and the plants and animals that live there. I discovered that everything was affected negatively. And we feed those plants to the communities and people on the planet who depend on them.

“This is another sign of what scientists are predicting is the impact of inadequate reductions in fossil fuel pollution,” NOAA Administrator Rick Spinrad said in a statement.

Approximately 4 million people live north of the Arctic Circle. It’s a geopolitical choke point, where shipping is beginning to become more accessible as sea ice recedes, leading to territorial tensions between nations and competition for minerals and oil.

The North Pole is also important for Earth’s climate, as it drives low-latitude ocean and atmospheric currents. This is where scientists can observe discrete changes as average temperatures rise, such as when reflective sea ice turns into open ocean that absorbs sunlight, or when precipitation falls as rain rather than snow. It’s one of the regions.

Now, scientists can add arctic tundra to that list.

In most ecosystems, plants absorb carbon dioxide from the atmosphere. Those plants grow and die, and are eaten by animals that also grow and die. The carbon contained in their carcasses (lignin, cellulose, fatty acids, proteins, etc.) feeds microorganisms, which break down large molecules and return carbon dioxide to the air, completing the carbon cycle.

The tundra, a frozen, treeless arctic biome with long, dark winters and short summers, changes the balance of this cycle. Although it does not have the dense, fast-growing biomass of a tropical rainforest, its vegetation sucks in about 1 billion tons of carbon dioxide per year, equivalent to nearly one-fifth of humanity’s total annual production. I will. Beneath the tundra is permafrost, a layer of soil that remains frozen year-round, repelling microorganisms that would normally decompose plants. As a result, vast amounts of carbon accumulate in Arctic soils, exceeding 1.6 trillion tonnes across the region. This is about twice the amount of carbon in the atmosphere.

But as the average global temperature rises, permafrost becomes less “permanent,” and dormant microbes begin to wake up with appetites and chew up organic matter in the soil. This leads to increased emissions of not only carbon dioxide but also methane, an even more powerful greenhouse gas. Over the years, melting permafrost has changed the carbon balance, reducing absorption and increasing emissions in the Arctic (side note: ice “melts” and permafrost “thaws”). This year, nine of the 20 permafrost monitoring sites reported record high temperatures.

However, it is not always a simple mechanism. “Rising temperatures tend to increase carbon dioxide uptake during the summer months,” Brenden Rogers, a scientist at the Woodwell Climate Research Center who contributed to the Arctic report card, said at a press conference. “However, the net carbon footprint of soil microorganisms also increases in the fall, winter, and spring.”

Another factor that has firmly turned the Arctic tundra from a carbon sink to a carbon source is wildfires. Notably, wildfires have occasionally occurred in the Arctic region in the past, but their frequency and severity have increased in recent years. Looking back over the years from 2001 to 2020, researchers found that fires are a major source of greenhouse gases and an urgent and persistent concern for residents of the Arctic. Last year was the worst wildfire season on record in the Arctic, and this year was the second-highest year for wildfire emissions.

The fires can then create a feedback loop that leads to further thaw of permafrost, causing more terrain to start burning.

If global temperatures drop, the tundra could flip in the opposite direction and become a net sink.

Rogers said there was wide variation in the amount of carbon dioxide absorbed by the region from year to year, indicating short-term factors were at play. However, the results highlight that humans cannot take for granted the traditional biomes that absorb carbon. It’s not just greenhouse gas emissions from burning fossil fuels that cause global warming. It’s also the loss of an important natural system that was used to offset heat-trapping gases. And the effects are already starting to appear.

“We are now together seeing impacts in real time in the Arctic. This is a call to action,” Spinrad said.