It also provides more fuel to burn; dried plants above ground ignite more readily than permafrost, which is made from frozen dirt or sand or gravel mixed with dead plants.
After analyzing satellite and aircraft imagery going back to the 1950s, scientists calculated that thermokarst formation has accelerated by 60 per cent since then.
“If you follow those pits over years to decades, they start to grow and keep growing and getting larger and larger and larger over time.
These typically trap a layer of snow on the ground; the snow insulates the earth by bouncing the sun’s energy back into space.
That’s allowing vegetation to dry out more easily and giving it more opportunities to ignite during increasingly frequent lightning storms. Hotter temperatures due to climate change already trigger the thawing that creates thermokarst, the way an ice cube might melt slowly on your countertop.
To make matters worse, the wildfire darkens the ground by charring it, so it will now heat up even more quickly in the sun.
Permafrost is basically a refrigerator for organic matter — and if it warms and thaws, microbes start to proliferate within it, just as they would on your food if you unplugged your fridge.
So a landscape that was once fairly dry, with carbon locked in the ground, is now much more actively belching emissions.
“Presently, most studies — especially modelling works — are focused on gradual permafrost thaw, which releases carbon from ground surface,” says Chen.
Across the Arctic, hotter temperatures are already pockmarking landscapes with thermokarst pits, but climate change is also changing the wildfire “regime,” or the way that blazes start and behave.