In a real clash of fire and ice, a massive wildfire in southern Greenland has captured the world’s attention.
At the end of July, a couple of NASA satellites detected hot spots in Greenland that indicated fire, said Mark Ruminski, a team leader for a hazard mapping system of the National Oceanic and Atmospheric Administration. But fires are unexpected in Greenland, so he and his team thought it might be an error in the data.
Then a civilian pilot snapped pictures of a wildfire near Sisimiut, the second-largest city in Greenland. When clouds cleared a few days later, NASA’s Landsat 8 satellite and the European Space Agency’s Sentinel-2 satellites captured photos of the largest of the fires from high above.
Although ice covers nearly all of Greenland, fires do occasionally break out on the ice sheet’s margins. Hearing of the new sightings, Stef Lhermitte, a geoscientist who specializes in remote sensing at Delft University of Technology in the Netherlands, reviewed the past 17 years of data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) satellite and threw together a quick analysis on Twitter to help give context to the situation.
I quickly made an overview of the MODIS active fires since 2000 over Greenland ifo confidence level. Many low confidence fires in the past pic.twitter.com/iEwJfDCz8W
— Stef Lhermitte (@StefLhermitte) August 7, 2017
MODIS data on Greenland fires stretching back to 2000 show spikes in 2015 and 2017:
To wrap up: wildfires have occurred in the past over Greenland but 2017 is exceptional in number of active fire detections by MODIS pic.twitter.com/2HGaVieTEe
— Stef Lhermitte (@StefLhermitte) August 7, 2017
Mark Parrington, an atmospheric chemist who works with the European Union’s Copernicus Earth observation program, also tweeted an analysis of carbon dioxide emissions that indicates spikes of fire activity in 2015, 2016, and 2017.
No Fuel, No Fire
Although the current fire’s cause remains a mystery, peat from thawed permafrost could be its fuel, said Jessica McCarty, a geographer at Miami University in Oxford, Ohio, who specializes in geospatial analysis of wildfires.
Permafrost, or permanently frozen soil, lies under multiple meters of an “active” soil layer that thaws seasonally. But in certain areas, when ice within the thawing permafrost layer melts, it can expose peat, a material that forms after decomposing plants get smashed down for centuries.
The peat is made up of organic matter, most notably carbon, McCarty said. Given how readily it burns, she added, it’s almost like one giant charcoal briquette.
McCarty suspects the fire’s fuel is peat for several reasons. First, the fire isn’t moving, like it would in a forest (not that there are any trees to speak of in this region of Greenland, she noted). In addition, the fire’s smoke is white, indicating damp fuel, like freshly thawed permafrost.
If the fire is being fueled by thawed permafrost, there may be underlying climate change implications, McCarty continued. “The climate change [connection] is that there would be no fires here in Greenland if there were no fuel, and the only way that there’s fuel is if the permafrost is [thawed].”
“Personally, this is very disturbing to me,” McCarty said, because the fire indicates significant permafrost degradation “sooner than [scientists] thought it would happen.” Researchers project significant permafrost loss in Greenland by the end of the century. Not 2017, she said.
In 2011, scientists at the University of Alaska Fairbanks modeled the fate of Greenland’s permafrost under a changing climate. Researchers study permafrost because of its potential to thaw and subsequently release carbon—in the form of methane and carbon dioxide—into the atmosphere. Permafrost makes up about 80% of Greenland’s land that’s not perpetually buried under ice.
The researchers wanted to know how much climate change would contribute to permafrost degradation, which is the decrease in the thickness of the permanently frozen soil. Their models revealed that by the end of the century, parts of Greenland could warm 1.99°C and that the active top layer of soil could extend downward an additional 44 centimeters, meaning that there would be less ice locking in carbon.
“Most of the terrestrial [ice-free] portion of Greenland is at risk of permafrost degradation,” wrote Vladimir Romanovsky, a permafrost researcher at the University of Alaska Fairbanks and a coauthor on the research. Especially in southern Greenland, where the fire currently burns, permafrost degradation has already begun, Romanovsky told Eos.
Natural Versus Unnatural
Southern Greenland is already warmer than the northern region naturally, Romanovsky said, so its permafrost is more vulnerable to begin with. Because the Little Ice Age ended in the past 150–200 years, some warming, and thus degradation, is natural.
Other factors contributing to permafrost degradation include glacial meltwater and human activities like constructing roads and buildings. Rising temperatures from the past 20–30 years of anthropogenic climate change have probably contributed as well. And when the ice in the ancient soils melts, it can expose peat to drier conditions—a perfect recipe for fire, Romanovsky said.
Then, in a feedback loop, “fire itself will add to the problem and accelerate [thawing] of permafrost,” he continued, which will cause more ice in the permafrost to melt and drain away and lead to further drying.
Fire Meets Ice
The fire poses another threat, McCarty said. It could release black carbon, which might fall onto the nearby ice sheet and accelerate its melting. Burning of biomass like peat, among other things, releases black carbon, which is much darker than ice. Black carbon deposited onto ice sheets lowers the ice’s ability to reflect sunlight and boosts its heat absorption, McCarty said, potentially speeding up melting.
As of Tuesday, the wind was blowing smoke from the fire over the ice sheet, McCarty said. She has already started analyzing how much black carbon it might deposit.
Unfortunately, there’s no telling when the fire may end, McCarty said. The longer it burns, the more it exacerbates the black carbon problem. With little to no rain in the forecast, Greenland’s options are limited, she continued. Officials could either attempt to transfer water into extremely remote areas to quench the flames or wait until the year’s first snow, which will most likely fall next month.
—JoAnna Wendel (@JoAnnaScience), Staff Writer