Like their undead namesakes, these so-called “zombie fires” are tough to kill.
Fed by fuel-rich soils in the Northern Hemisphere and subsisting on the meager oxygen available beneath the snow, zombie fires can smolder for months, long after flames above ground have been extinguished.
And sometimes, fires that have burned all winter long can ignite new blazes the following year after the snow has melted.
Sander Veraverbeke, an associate professor at Vrije Universiteit Amsterdam, first suspected this phenomenon was sparking wildfires several years ago. Scanning satellite images for an earlier study that examined the role of lightning in triggering Arctic fires, Veraverbeke said he noticed new fires were igniting near land that had burned the previous year.
“I saw that on the edges of the fire scars from the year before, flames were popping up again in spring and new forest fires were starting on the edge. And to me, that was really intriguing,” he said.
Veraverbeke said that local fire managers confirmed that they too had observed fires that seemed to survive the winter.
Still, it was unclear how widespread these zombie fires were — and whether they were becoming more frequent.
In a new study published Wednesday in the journal Nature, lead author Rebecca Scholten of Vrije Universiteit Amsterdam, along with Veraverbeke and other co-authors, attempt to answer these questions.