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Warming temperatures and increased precipitation in the Canadian High Arctic are mobilizing new pathways for subsurface contaminants to spread from more than 2,500 contaminated sites associated with industrial and military sites across the region.

The pathways are routes for groundwater to discharge to rivers and lakes, a process which the researchers predict will eventually take place year-round. During the Arctic winter, the ground is frozen, and groundwater does not flow. But, during the warmer summer, shallow groundwater is mobilized and may enhance the migration of contaminants. Groundwater discharge is the process by which water moves from underground aquifers to surface lakes or rivers.

Arctic sites underrepresented in permafrost research

The study, published in Hydrological Processes, focused on the BAF-3 radar station on Brevoort Island, Nunavut. The station is one of 21 Cold War-era radar installation sites in northern Canada that are still contaminated by industrial waste. BAF-3 is still in use as part of the North Warning System, a joint Canada-U.S. air defence network.

鈥淭his site is unique in that it鈥檚 one of the few places where we can model changing hydraulic processes that could increase contamination risks in the High Arctic,鈥� said Selsey Stribling, PhD graduate and study co-author. 鈥淲e were very interested by this idea and understanding how groundwater behaves there.鈥�
Groundwater in the High Arctic has been understudied due to extreme costs and logistical challenges.

Groundwater movement creates contaminant pathways 鈥� and increases thaw

Working with supervisor Jeffrey McKenzie, professor in the Department of Earth and Planetary Sciences, Stribling modelled how shallow groundwater flows towards a freshwater lake. The team used SUTRA 4.0, a unique numerical model that simulates both groundwater flow and freeze鈥搕haw processes. Climate predictions from the International Panel on Climate Change were used to simulate short-, medium- and long-term scenarios up to the year 2100.

The results showed that as the active layer of permafrost 鈥� the top layer of soil that freezes and thaws seasonally 鈥� thickens and remains thawed longer, the risk of year-round contaminant transport into freshwater lakes increases. The simulations also showed a feedback loop: increased groundwater movement contributes to further thawing, which in turn accelerates discharge and deepens the active layer. The results demonstrate that the combination of both a warmer and wetter future Arctic further enhances the predicted changes.

Understanding the impact

Given the scale of contamination, the findings have serious implications for fragile northern ecosystems.

鈥淲e have these contaminants that have sat immobile and frozen in the environment for decades. As the active layer thaws and the permafrost degrades, you're creating new groundwater pathways that allow the contaminants to be mobilized and transported by groundwater toward other environments, as well as streams and local water bodies,鈥� Stribling explained.

While they say drinking water sources are closely monitored, the researchers caution that impacts on wildlife and food chains remain a concern.

鈥淭he thought was, 鈥楾hese are frozen, contaminated sites, this stuff isn鈥檛 going anywhere.鈥� But now the Arctic is warming three to five times faster than the rest of the planet,鈥� McKenzie said. 鈥淲ith such an incredible number of contaminated sites becoming more active with climate change, you may have potential year-round mobilization of contamination because of the year-round movement of liquid water.鈥�

Further data required

Remediation is planned for BAF-3, but costs are high and data gaps remain. The researchers say more site-specific data is needed to assess contamination risks and help governments plan cleanup efforts.

They also emphasize that future climate modelling must account for differences between lakes and rivers, which behave differently and should be considered separately.

鈥淲e need to think about ways to identify sites, clean them up and know where they are,鈥� McKenzie said.

About this study

鈥�,鈥� by Selsey Stribling, Pierrick Lamontagne-Hall茅, Dylan Hemmings, Tom MacNeil and Jeffrey McKenzie,聽was published in Hydrological Processes.

The research was funded by , an engineering firm contracted by the Government of Canada.