“Zombie fires” destroy forests in the Arctic. Scientists have found that the fires do not disappear completely even in winter, but go underground, where they smolder in peat until spring. With the onset of warm weather, fires flare up with renewed vigor. Where are thermopoints hiding under the snow now in the Siberian taiga? And what else did experts find out during the study of “zombie fires”?
South-west of Yakutia, right-bank part of the Vilyuy river valley, Suntarsky ulus. Local residents found that smoke is coming out from under the snow in 40-degree frost. In this place, as in many other regions of the republic, in the summer forest fires raged.
Horse fire spreads very quickly. Avialesookhrana firefighters and volunteers from among local residents stopped the fire eight kilometers from the village of Kutana. However, it was not possible to completely destroy the fires – in the autumn the fire went underground. In October, smoldering peat bogs were dug in and flooded with tons of water. But it continued to burn in the winter. And this is far from the only thermal point on the map of Yakutia.
In the spring of 2020, NASA specialists noticed a huge thermal anomaly in the north of the republic. The hotspots were precisely in those areas where the worst forest fires blazed last summer. “Residual” or “overwintered” fires are not a new phenomenon, but in winter, under snow, in the Arctic tundra, this has never happened before.
Similar “zombie fires” from space were recorded and in the Suntarsky ulus last autumn – only about a dozen thermopoints.
In the summer of 2021, wildfires were the worst on record. Siberia, Canada, Alaska and even Greenland suffered from them. The smoke reached the North Pole. Most of all, specialists are alarmed by the trend of recent years – winter peat fires are shifting further and further north.
Researchers from the Free University of Amsterdam analyzed satellite data from the forests of Alaska and northern Canada from 2002-2018. They found that most of the winter foci coincide with the summer ones.
During “hibernation” the fire moves slowly, spreading throughout the winter at a distance of 100 to 250 meters. In the spring, usually one and a half to two months after the snow melts, an outbreak occurs. Winter “zombie fire” often burns out the root system and soil under the trees that survived the summer fire – they die and fall closer to summer.
Sometimes an “overwintered” fire turns out to be extremely harmful. For example, in 2008, a fire that woke up burned almost 14,000 hectares in Alaska – more than a third of all forests burned in the state that year. And the fire that broke out in the fall of 2015 survived the winter, with the advent of spring it resumed within its previous boundaries and began to spread further, which is confirmed by satellite images. “Zombie fires” become especially strong when the smoldering fire has gone deep enough into the turf.
Peat is a product of incomplete decomposition of plant mass. The main combustible materials in its composition are carbon (more than half of the total mass) and hydrogen (about 5-6%). In addition, peat contains oxygen atoms bound in chemical molecules. This allows the peat to burn or smolder for a long time without air.
“Given the continuation of climate change, it can also be predicted that this problem will also increase in part of natural bogs, as they will dry out more often, more strongly, and such phenomena will occur on them with a greater probability,” notes the coordinator of the projects of the World Fund Forest Program Wildlife Konstantin Kobyakov.
Flameless combustion is very stable. It can last for years, even in spite of heavy rainfall. Putting out peat fires is very difficult. Water flows through the soil in small channels, leaving patches that continue to smolder. In addition, the outbreaks are located in hard-to-reach northern areas. Sometimes they can only be detected from a satellite, using remote sensing of the Earth.
With fires that now persist even in winter, boreal forests could be transformed from a major sink of carbon dioxide into a source of it.