Warming temperatures and increased precipitation in the High Arctic are creating new pathways for groundwater, mobilizing contaminants that have been locked in frozen soil for decades. As the permafrost thaws, this newly mobile groundwater is beginning to transport industrial and military waste into freshwater lakes and rivers, posing a significant threat to the region’s fragile ecosystems. This process, driven by climate change, is predicted to accelerate, with groundwater eventually flowing year-round, fundamentally altering the Arctic’s hydrological systems.
Beyond the risk of contamination, the surge in Arctic groundwater is also releasing vast quantities of carbon into the ocean. Research reveals that this subterranean flow, though small in volume compared to rivers, carries a disproportionately large amount of organic carbon and nitrogen, contributing to ocean acidification and potentially turning Arctic coastal waters into a new source of atmospheric carbon. This hidden flux of greenhouse gases represents a previously underestimated factor in climate change models and highlights the complex, cascading effects of thawing permafrost on a global scale.
Thawing Ground Unlocks New Pathways
The Arctic’s warming, occurring at a rate twice the global average, is degrading the permafrost that underpins the region. This thawing of what was once permanently frozen ground is creating and expanding subsurface pathways for water to move. The active layer of permafrost—the top layer of soil that freezes and thaws seasonally—is thickening and remaining thawed for longer periods. This transformation is turning previously impermeable permafrost into new coastal and submarine aquifers, a change that scientists are observing in real-time. As Bayani Cardenas, a professor at the Jackson School of Geosciences, noted, “The Arctic coast is changing in front of our eyes.” This fundamental shift means that systems once dominated by surface water are transitioning to groundwater-dominated systems, a change with profound impacts on the entire hydrological cycle of the Arctic. This allows not only for the increased flow of water but also for the transport of anything contained within the soil.
Contaminant Mobilization and Spread
Across the Canadian High Arctic, more than 2,500 contaminated sites, legacies of past industrial and military activities, are scattered across the landscape. For decades, the contaminants at these sites have been largely immobile, trapped within the frozen ground. However, the new groundwater pathways created by thawing permafrost are now mobilizing these hazardous materials. According to Selsey Stribling, a co-author of a recent McGill University study, “We 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.” While drinking water sources are being monitored, the potential impacts on wildlife and the broader food chain remain a significant concern.
A Self-Perpetuating Cycle
The relationship between groundwater and permafrost thaw is not a simple one-way street; it’s a feedback loop. Research simulations have shown that the increased movement of groundwater itself contributes to further thawing of the permafrost. This, in turn, accelerates the discharge of groundwater and deepens the active layer, creating a self-perpetuating cycle that could lead to more rapid environmental changes than previously predicted. A future Arctic that is both warmer and wetter will further enhance these predicted changes, leading to even greater groundwater flow and contaminant spread.
A Hidden Surge of Carbon into the Ocean
While the threat of legacy contaminants is a major concern, the thawing Arctic landscape is also releasing enormous amounts of organic carbon into the ocean through groundwater. Researchers studying the Beaufort Sea coastline found that groundwater is releasing an estimated 230 tons of organic carbon per day during the summer months. This amount is surprisingly high, on par with the total carbon released by all the rivers in the area during the same period, despite the groundwater making up only a small fraction of the total water discharge.
The Scale of the Carbon Release
Cansu Demir, who led the research while at the UT Jackson School of Geosciences, described the findings as showing “humongous amounts of organic carbon and carbon dioxide released via fresh groundwater discharge in summer.” The permafrost acts as a vast subterranean reservoir of organic material. As it thaws and becomes part of the groundwater flow, the water picks up this carbon and transports it to the coast. This process is so significant that it has the potential to alter the carbon balance of Arctic coastal waters. Demir suggests that as the flow of submarine groundwater increases, the outflow of carbon from the shore to the sea could effectively make the ocean’s surface a net source of carbon to the atmosphere.
Ecological Consequences for Arctic Ecosystems
The massive influx of carbon and nitrogen from groundwater into the Arctic Ocean is expected to have significant ecological consequences. One of the primary concerns is ocean acidification. The increased carbon content can lower the pH of the water, making it more acidic. This change in ocean chemistry can harm marine organisms, particularly those that build shells or skeletons, such as crustaceans, clams, and snails. These creatures, which form the base of many marine food webs, could become increasingly vulnerable as acidification intensifies. The delicate balance of the Arctic’s coastal ecosystems, already under stress from warming water temperatures and sea ice loss, now faces an additional threat from the changing chemistry of the water itself. The full impact on wildlife and food chains remains an area of urgent research.
Modeling Future Scenarios
Understanding and predicting the behavior of Arctic groundwater is a significant challenge due to the extreme costs and logistical difficulties of conducting research in the region. To overcome these obstacles, scientists are increasingly turning to sophisticated computer models. In a recent study, researchers used a unique numerical model called SUTRA 4.0, which can simulate both groundwater flow and the complex processes of freezing and thawing. By applying climate predictions from the Intergovernmental Panel on Climate Change, the research team was able to model short-, medium-, and long-term scenarios, extending to the year 2100. This study, which focused on the BAF-3 radar station on Brevoort Island, Nunavut, provided crucial insights into how groundwater flow toward a freshwater lake would change under different climate scenarios. The results confirmed that as the active layer thickens, the risk of year-round contaminant transport into freshwater bodies increases significantly, highlighting the power of such models to forecast future environmental risks in this remote and critical part of the world.
