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Covering much of the Arctic tundra is a mass of carbon-rich frozen soil, or permafrost. This permafrost layer sequesters carbon from the atmosphere and stores it under wetlands for tens of thousands of years.
Frozen soil is insulated by a cold, moist blanket of plant litter, moss, and peat. But when that blanket is incinerated by tundra wildfires, the permafrost becomes more susceptible to thaw. Then, as permafrost thaws, ancient carbon is released, which microorganisms in the soil convert into methane. Methane is a powerful greenhouse gas, and its emissions contribute to climate change and the fundamental reshaping of northern latitudes around the world.
the study published last month environmental research lettersThe journal Science found that methane hotspots in the tundra are more likely to be found in areas where wildfires have recently occurred. The study focused on the Yukon-Kuskokwim region, Alaska’s largest delta, an area that has long been known to emit large amounts of methane.
A team of scientists participating in NASA’s ABoVE project (Arctic-Northern Vulnerability Experiment), which studies environmental change in Alaska and western Canada, was curious about the causes of methane hot spots observed in aerial surveys in 2018. Ta. So Elizabeth, the lead author, and Joseph, who was an intern at the time, superimposed maps of those areas with recent fire activity.
Her team found that hotspots are almost 30% more likely to develop in areas that have experienced wildfires in the past 50 years than in unburned areas, and that the likelihood of hotspots occurring increases when water touches the area surrounding the fire. found that it jumps to nearly 90%. Recently burned wetlands with particularly carbon-rich soils had the highest proportion of hotspots. “Fires have an important effect on increasing emissions,” says Yosef.
Merritt Turetsky, an ecologist at the University of Colorado Boulder who was not involved in the study, said the large-scale discovery, which covers about 700 square miles in Alaska, will help complement field measurements. . “There really needs to be a glue between what’s happening on the ground and what we can detect from satellite images,” she says. Aerial surveys help scientists understand the vast tundra. Field surveys are limited there by road networks that tend to avoid wetlands.
The effects of permafrost thaw have spread far beyond the Far North. The effects of wildfires on frozen permafrost drive climate feedback loops. Wildfires release methane, accelerating climate change and causing more frequent and recurring wildfires.
Tundra fires are still relatively rare, but are expected to increase due to rising temperatures and increased lightning activity. Some estimates predict that wildfires in the Yukon-Kuskokwim Delta could quadruple by the end of this century. With no tall trees for flames to climb, tundra fires creep slowly along the ground, smoldering for months, sometimes going underground and reemerging later.
The potential impacts are significant, given the amount of carbon frozen beneath Arctic soil. Arctic permafrost is a vast reservoir that stores an estimated 1.7 trillion tons of carbon. This is more than 50 times the total carbon emitted as fossil fuel emissions worldwide in 2019.
“If we want to have any certainty about our climate future, we all need to invest in these temporary large-scale greenhouse gas emissions,” Turetsky said. There is evidence that the tundra is transforming from a carbon sink to a carbon (and methane) source. “Wildfires certainly don’t help,” she says. “That’s a big deal. It’s a turning point.”