For decades, companies exploring for oil and gas in the Arctic's remote southern reaches have disposed of their drilling waste in the cheapest and most convenient way possible: by digging massive pits to hold the waste and then capping them with frozen permafrost. And for decades, the waste harmlessly sat in the frozen tombs.
Then climate change, which scientists say is caused by burning fossil fuels, set in, causing the permafrost to begin melting.
In the Mackenzie Delta region of Canada's Northwest Territories, scientists have discovered unusually high salt levels in some freshwater lakes, and the salinity could be transfiguring the foundation of the local food web. In a study published this month in the journal PLOS ONE, researchers say this is being caused by leakages from the frozen waste pits, known as "sumps."
Joshua Thienpont, lead author of the paper while he was a Ph.D. student at Queen's University in Kingston, Ontario, said the study should cause companies drilling for oil in areas with rapidly thawing permafrost to reconsider using sumps for waste storage.
"We need to be cognizant of the fact that these sumps are not really a permanent containment mechanism in an area of warm permafrost," said Thienpont, who is now a postdoctoral fellow at Brock University in St. Catharines, Ontario.
Salt in fresh water
Thienpont and his colleagues looked at 101 lakes in the Mackenzie Delta, some near drilling sumps, some near areas of major permafrost thaw -- confusingly known as "slumps" -- and some near neither. Most of the sumps had been built in 1970s.
After examining the water chemistry from the lakes, the researchers found "clear evidence" of elevated levels of salt in as many as 15 of 20 freshwater lakes with sumps nearby.
"You're in a very low chloride area, a very low salt area, and what came out quite clear was that chloride was coming out," said John Smol, a paleoecologist at Queen's and Thienpont's Ph.D. supervisor.
Smol said it was important to differentiate between changes in water chemistry that might have been a result of sump leakage or a result of natural permafrost thawing. But he said they found relatively normal salt levels in the lakes near permafrost slumps, compared with those lakes near waste sumps.
Smol also said the researchers were unsure whether other chemicals were also leaking into the lakes from the sumps. Pretty much all drilling waste includes potassium chloride to help keep equipment from freezing, but other substances in the waste can vary from company to company, and the specific chemicals are the proprietary knowledge of the company, Smol said.
"Different companies probably used different compounds," he added. "The common thread should've been chloride, and that came out. It's elevated."
Thienpont and his team also began assessing the impacts of the leaks on the local ecosystem. The team took sediment samples from the lakes, which contained remnants of fossilized water fleas.
By examining the fossilized water fleas, they were able to reconstruct when the fleas were alive and what their biological characteristics were. And according to Smol, they discovered that salt-loving water fleas came to dominate the flea population shortly after sumps were built near the various lakes.
Smol said they're unsure what the ecological impact of the shift could be, and they haven't confirmed any other major ecological changes, but he said it's still a worrying observation.
"Invertebrates are not insignificant," he said. "They're part of a food chain."
Thienpont said he'll investigate other biological communities in the sediments to assess whether there have been other ecological impacts.
"This is the first snapshot of what's going on," he said.
Drilling boom on the horizon
With the old sumps becoming an ever-riskier waste disposal solution as Arctic permafrost thaws, the region is about to experience a major uptick in oil and gas exploration and drilling.
And although the sumps Thienpont and his colleagues examined were built decades ago, seven sumps were constructed between January 2009 and June 2011, according to Northwest Territories government records viewed by the Vancouver Sun.
Northwest Territories government officials also estimate that energy companies have committed to spending $637 million to explore the area.
Petroleum giant ConocoPhillips Co. is developing a $16 billion natural gas project in the Mackenzie Delta, featuring a 743-mile pipeline system along the Mackenzie Valley, which the company hopes will transport about 800 million cubic feet per day of natural gas over the 24- to 30-year life of the project.
The region could hold as much as 64 billion cubic feet of natural gas, Smol said, and sumps remain the recommended method of waste disposal under federal guidelines for drilling in the Arctic.
"This is going to be a major area for hydrocarbon development," Smol said.
"We're not saying, 'No development,' but we're saying, 'Be cautious,'" he added. "There's enough evidence here that you should be very cautious."