Scientists may know why snow-buried ‘zombie fires’ resurrect in spring

Where there’s smoke, there’s climate change

While there are suspicions that zombie fires stem from surface fire remnants, scientists believe atmospheric warming may cause underground smoldering without a spark, potentially indicating spontaneous combustion due to climate change.

As explained in the study, there are records of these fires dating back to the 1940s.

However, their frequency has increased, which goes hand in hand with accelerated warming.

Mathematical models for “what-if” scenarios

In the research, scientists presented mathematical models they developed for various “what-if” scenarios. It was important to include how temperature and carbon content in peat soils respond to changes in weather and climate.

This is significant because the model also takes into account the heat generated by certain microbes as they break down soil, releasing carbon. This approach yielded two notable findings, as reported by the researchers.

The first showed that microbes can generate so much heat that underground peat can smolder at around 80°C during the winter, ready to combust in the spring. This can happen regardless of the temperatures and without any previous fire.

“We call this new state the hot metastable state of peat soils. In this context, “metastable” means a long burn – the hot state lasts for a long but finite time, up to ten years until the peat burns out,” they explained. 

The second result showed that sudden transitions from the regular cold state to the hot metastable state can be triggered only by realistic climate patterns. That includes summer heatwaves and global warming scenarios.

Most interestingly, the increase in atmospheric temperature must be faster than a certain critical rate to trigger the transition. If the atmospheric temperature increases by the same amount but at a slower rate, the bioactive peat soil remains in the regular cold state and never transitions to the hot metastable state.

Real-world

Researchers currently lack concrete evidence of this phenomenon occurring in the real world, and it has yet to be replicated in a laboratory setting.

“We still do not have proof that this happens in the real world, nor has it been demonstrated in the laboratory – for now, this is a phenomenon seen only in our models,” researchers said.

They suggest that atmospheric temperature itself is not the key critical factor for ‘zombie fires.’ Instead, it is the rate of atmospheric warming that causes long-lasting underground peat combustion.

Weather extremes are concerning in this case due to their impact on the occurrence of this type of fire. As the climate heats up, extreme weather is on the rise, potentially fueling more zombie fires. This worrying trend could trigger a dangerous cycle: massive amounts of carbon released from ancient peat soils could worsen climate change, leading to more fires, even harsher weather, and so forth.

To prevent more zombie fires, the key solution seems to be controlling climate variability, as scientists explained. While policymakers concentrate on high temperatures, it’s also crucial to manage how quickly the climate shifts.

The research was published in The Conversation.