Smoke from Canada’s wildfires, which have burned vast tracks of forest in B.C. and the Northwest Territories, has been spotted as far away as Portugal.
And its travel is fuelled in part by incredible clouds created by the fires that act like chimneys funnelling smoke and ash as high as 10 to 15 kilometres into the atmosphere.
“The smoke is often injected all the way up into the stratosphere,” says Scott Bachmeier, a meteorologist at the University of Wisconsin-Madison, who tracks the pyrocumulonimbus clouds, or pyroCbs, created by intense boreal wildfires.
Once in the stratosphere, the smoke layers “can easily circle the globe,” says Bachmeier.
He and his colleagues have spotted 10 pyroCbs created by Western Canada’s boreal fires so far this year. He expects to see plenty more as hot, dry conditions continue in much of British Columbia and the Northwest Territories, where more than a million hectares has already gone up in smoke.
The smoke, which has been casting an eerie pale over Yellowknife, can also been seen from space.
“Some plumes appear to have moved south and east into the northern plains of the United States while others can be spotted over the Canadian Maritimes and as far east as Portugal,” NASA reports on its Earth Observatory.
The pyroCbs and their “cauliflowery” clouds rising up out of the fires can also be seen by satellite, which over the years have captured some remarkable images of the clouds exploding into the stratosphere.
Scientists say pyroCbs appear to be more common to fires in Canada, Alaska and Russia, than those in the tropics.
Dense, dry stands of spruce in the boreal forest make for a “pretty volatile mixture,” says Douglas Morton, an earth scientist at NASA, working to get a better read on forests and the fires that can impact everything from greenhouse gas emissions to melting ice sheets.
“It’s a major event in the life of the earth system to have a huge set of fires like what you are seeing in Western Canada,” Morton said in an interview from the Goodard Flight Centre in Maryland. They not only impact the atmosphere, he says, but can alter much solar energy reaches the earth and the distribution of carbon, nitrogen and phosphorus over large areas.
Boreal fires can get incredibly intense and cover tens to hundreds of kilometres as flames jump from the crown of one tree to the next, releasing not just smoke and heat but moisture as the trees burn.
PyroCbs are massive anvil-shaped towers of cloud that resemble thunderclouds. They form when emissions from intense fires rise and begin to cool and condense. Powerful pyroCbs can “punch” right through the boundary of the lower atmosphere, which is about 10 kilometres above the ground, says Mike Flannigan, a specialist in wildland fire at the University of Alberta.
When this happens they inject their smoke and soot into the stratosphere and “it can take years to settle out,” says Flannigan, noting that volcanoes can do the same thing, though on a larger scale.
“You transport everything — the smoke, the greenhouse gases, the black carbon,” NASA’s Morton says of pyroCbs. Black carbon, a major component of soot, from fires is a concern as it can speed melting of glaciers and ice sheets as the dirty specks absorb solar heat.
Bachmeier says scientists have only realized pyroCbs can be a major source of stratospheric pollution in the last 15 years. He and his colleagues from several agencies and universities around the world are now tracking the pyroCbs to find out if they are becoming more common as the climate changes.
“That’s the elusive question that we are trying to answer,” he says. “By beginning to catalogue the pyroCb events, we can start to gather some concrete numbers with which to begin comparing yearly global trends.”
Banner year for wildfires
When the smoke settles, 2014 will likely be another banner year for wildfire in Canada.
“The official report is about 1.1 million hectares burned in the Northwest Territories, but I think it’s closer to 2.5 to 3 million,” says Mike Flannigan, a wildfire expert at the University of Alberta.
He says people are so busy dealing with the fires, which have been burning for weeks in the Northwest Territories, they have yet to map and register the total damage.
July is “prime burning season” in most of Canada’s boreal forest while August tends to be the busiest month for fires in B.C., says Flannigan, who predicts fire could consume four million hectares of Canadian forest this year.
That would be twice the annual national average and close to what burned last year when fires tore across Quebec.
He says Canadian fire managers are becoming more “progressive” and now let fires run their natural course if they don’t threaten communities.
But there are signs climate change is also increasing boreal wildfires, says Flannigan, a former senior research scientist at the Canadian Forest Service.
His work indicates the area burned in Canada has doubled in the last 40 years. And this year’s fires in the Northwest Territories appear to be consistent with changing climate.
A ridge of hot, dry air has been “stalled” over the Northwest Territories for weeks fuelling the fires, he says, and appears to be linked with a weakening of the jet stream in the atmosphere.
The same phenomena — stalled weather systems — have been linked with extreme weather seen around the globe from the rains that caused the unprecedented floods in Saskatchewan and Manitoba in July to the prolonged deep-freeze in much of eastern North American last winter.
“These weather systems just persist and this is consistent with the weakening jet stream theory,” says Flannigan, noting that both weather extremes and forest fires are expected to grow as the climate continues to changes.
“If you think the weather is wacky just wait another 10 years, “says Flannigan. “It is going to get wackier.”