by Erling Friis-Baastad
For Yukoners, climate change brings a special concern: the ground under our feet shifts as permafrost thaws. This causes highways to heave, land to settle and buildings to buckle. That’s why a team of surficial (or earth-surface) geologists, cartographers and permafrost researchers are mapping current and potential landscape hazards near Yukon communities.
Despite such readily visible havoc, many northerners aren’t sure what permafrost is. “We often think of permafrost as being soil with ice in it, but that’s not encompassing all that could be permafrost,” says hydrologist Bronwyn Benkert of the Northern Climate ExChange, who is the project co-ordinator.
Any ground material frozen for more than two years can be called permafrost, says Benkert. Even “bedrock could be considered permafrost if it’s at a temperature of zero degrees for more than two years,” she adds. In other words, permafrost may be more widely spread and show up in a broader variety of forms than we ever expected. This demands a multifaceted, flexible research approach in a number of disciplines.
While geologists, hydrologists and their students are necessary members of her permafrost teams, local residents also play an essential role, says Benkert. “At the start of a project, we have an open house and invite members of the community to come and tell us about areas of concern - where they’ve seen permafrost melting or where they’re concerned about flooding - so we can incorporate those concerns in the case studies,” she says.
To help maintain that communication over the course of the project, a local resident is often hired to serve as a liaison between the scientists and the community.
“At the end of the project, we have a wrap-up event,” Benkert says. “So when we were done in Burwash, we did a bingo and dinner and then put our maps up and had a conversation about what we found as part of the project.”
The researchers also use data developed on the other side of the border to help them prepare for each study area. SNAP, Scenarios for Alaska Planning, is connected with the University of Alaska Fairbanks, but its research bailiwick includes the Canadian North.
SNAP provides the Yukon project with climate-projection models. “They incorporate them and downsize them to study areas we are interested in,” says Benkert, “so we have two-by-two-kilometre grids for climate parameters, temperature, precipitation, and freeze and thaw dates.” (An attractive, informative website for SNAP can be found at www.snap.uaf.edu/).
The Yukon field research proceeds in several stages and employs a host of techniques. First, a surficial geologist and student field assistants from the Yukon Geological Survey spend two or three weeks in the study area - about 100 square kilometres around a community - mapping landscape features. “They do it at a scale that’s never been done before in these communities,” Benkert says. At 1:25,000, that scale is very detailed.
Next, researchers, including professors and students from the universities of Ottawa and Montreal, employ three different techniques to explore beneath the surface.
First, using ground-penetrating radar, they transmit a signal into the earth, then analyze the patterns with which it bounces back. This allows them to create a permafrost profile.
Another set of researchers employs electrical resistivity tomography, which is similar to the ground-penetrating radar but is effective at greater depths.
A third group then drills permafrost cores and takes those back to the lab for analysis. Predictions about thawing can be made based on the nature of the sediment, including the size and proportion of soil grains, the moisture content and the amount of ice among the grains. The coring allows for a stronger vertical component - an essential second dimension on the map, says Benkert.
Different research regions can yield their own particular variations on the permafrost theme. For instance, near Burwash, in areas affected by forest fires, permafrost degradation has been accelerated. “One of the things that really protects permafrost is the mossy layer that grows on the surface,” Benkert notes. “Where that has been stripped, by construction or fire, the permafrost isn’t as well insulated.”
Meanwhile, on some mountains, especially near Dawson, temperature inversions are frequent, and since temperatures can rise the higher one climbs, inferences made on one mountain might not hold for another. A researcher is assigned to correlate such local anomalies with the overall map.
The fieldwork is undertaken in summer and fall, while winters are spent analyzing core samples and data. “Then we sit around the table, put our heads together and come up with a hazards rating,” says Benkert.
Each unit, or polygon, in a study area is ranked according to current permafrost conditions and hazards, as well as potential changes. The polygons are colour-coded, with red being high risk, yellow medium risk, and green low risk. “If you are a developer or a community that wants to build a new arena, you can take the map and say, ‘We want to be sure we site our arena in an area that’s of low risk of geological hazard or permafrost hazard.’”
However, Benkert adds, if they want to put the arena in an area that the researchers have identified as being medium risk, the proponents would do more site-specific studies and try to incorporate engineering that suits the demands of the site. Even a red, high-risk area isn’t completely off-limits to some forms of construction.
Thanks to community input, university researchers, Yukon Geological Survey personnel, and funding from Aboriginal Affairs and Northern Development Canada, four research projects in Pelly, Mayo, Destruction Bay, and Burwash have been completed since 2010. Faro, Dawson and one as-yet-unnamed community will be completed over the next two years.
Mudslides, road and runway washouts, flooding, sudden new thermokarst ponds and other such headaches are certain to occur in our otherwise uncertain future. The hazard maps will provide a tool so that the territory can meet these infrastructure challenges.
More information is available at www.yukoncollege.yk.ca/research/projects/
This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at www.yukoncollege.yk.ca