What is the zombie fire?

Most wildfires in the north are caused by lightning or man-made fires in the summer, and extinguished by rain and snow in the winter.

Rebecca Schulten, the lead author of the new study, said that some fires “managed to survive the winter through smoldering and a thick organic layer under the snow, then reappear and start a new forest fire in the next season. “

This “zombie fire” in Siberia Made headlines last springAnd was accused of helping to ignite In a record heat wave, the worst wildfire ever in the region.

Although this type of fire is often referred to as a “zombie fire”, scientists often refer to it as a “wintering fire.”

Scholten, a doctoral student at Vrije Universiteit Amsterdam in the Netherlands, said: “This hasn’t really disappeared. “It’s just in a different state. “

Richard Olsen, manager of firefighting operations at the Northwest Territories government, said that fire managers prefer the term “maintain firepower”, which has been used for decades.

Why do they seem to prevail in the north?

Scolten said that this type of fire is closely related to the boreal forest for two reasons:

• There is a thick layer of peat on the ground, which can provide fuel to make the fire smolder across the ground in winter.

• Snow in the northern winter can help protect fires by keeping moisture on top of the soil instead of soaking and extinguishing fires.

Researchers found that overwintering fires smolder in lowland areas, which are full of soil full of organic matter and taller tree cover, which makes the fire very intense.

How do researchers identify and count fires?

Merritt Turetsky, director of the Arctic and Alpine Institute at the University of Colorado Boulder, said that this is a challenging problem because the fire is very remote and therefore still “very mysterious” to us. He conducts wildfire research in northern Canada, but Did not participate in new research.

To spot the zombie fire, Scholten and her colleagues checked daily satellite images from 2002 to 2018. they:

• The location of the fire was compared with the location of the fire a year ago and observations on the ground.

• Check that these fires occur early in the season-overwintering fires tend to occur in the spring, before most storms and lightning start.

• By checking whether lightning strikes are detected in the area, and the location of roads and other infrastructure that may suggest a fire, other causes of the fire can be ruled out.

How big are these fires?

This is what the research is mainly trying to find out.

Sand Weaver Webeck, associate professor of climate and ecosystem change at Vrije Universiteit Amsterdam and the senior author of the new study, said that many news reports sound like almost all burnt areas in Siberia come from zombie fires. She said: “Obviously not true. .” Most fires are still caused by lightning or man-made. But it is not clear how widespread the zombie fire is.

Researchers found that in the Northwest Territories and Alaska, overwintering fires tend to be small and usually don’t contribute much to the total fire activity, with an average of less than one percent of the burned area.

However, they do have the potential to cause a lot of damage. According to the research report, in 2008, a winter fire in Alaska eventually burned 13,700 hectares, accounting for about 38% of the burned area that year.

Could they become more problems of climate change?

Scolten said that although the study did not last long enough to say with certainty, the data suggests that climate change may increase its frequency.

That’s because they tend to occur after hot summers and large and deep fires. “And we know that these events happen more frequently.”

What can the fire manager use this information for?

Scholten hopes that information about the time and location of a fire will make it easier to predict the location of a possible fire and help fire managers find the fire early.

Generally speaking, wildfires are regarded as part of the natural cycle and will burn unless they threaten human life and property.

But Veraverbeke said that given the increasing amount of carbon released into the atmosphere by wildfires, fire managers may consider extinguishing some large fires to prevent carbon emissions, and may wish to target certain types of fires.

He said: “These overwintering fires may be unpredictable because they are predictable.”

Turetsky said that Dutch researchers’ new technology can be used to create surveillance systems to track whether and for how long zombie fires have caused large-scale wildfires that produce large amounts of carbon emissions. She said: “That would be the worst-case scenario.” “Obviously, if it does happen, we want to know this.”

Olsen said fire managers are already monitoring fires, especially in areas where the fire threatened a year ago. But he said the new research provides useful information to help track fires and predict fires based on weather observations.

“Maybe this is something we need to track further to better understand [of] Whether the number, intensity or severity of remaining fires is and in fact is changing,” he said, noting that the new information in the study on the greenhouse gases produced by such fires is also useful for calculations in the area.

Mike Flannigan, professor of wilderness fires at the University of Alberta, said that this new tracking technology can also be used to see how big a zombie fire is in other places, such as Siberia. Flannigan suspects this. The place may cause more damage.