When winter descends on the Great Lakes, the surface transforms into a mosaic of frozen expanses, drifting ice sheets, and glittering shorelines. For centuries, these icy landscapes have been shaped primarily by the atmosphere: frigid winds, plunging temperatures, snow, and the dimming winter sun. But new research reveals that the unseen world beneath the surface—the steady, powerful pulses of groundwater seeping upward—may be just as influential in shaping how ice forms, melts, and holds together along the coasts of Lakes Michigan and Huron.
These two lakes, which together form one of the largest freshwater systems on Earth, are not just vast reservoirs of water; they are dynamic systems intricately connected to the land and aquifers that feed them. Scientists are now discovering that groundwater may carry enough heat to disrupt the balance of ice, particularly along the lake margins where humans and ecosystems interact most.
The Hidden Warmth Rising from Below
When we think about ice stability on lakes, we often picture surface-driven processes: cold air freezing water, sunshine melting snow, or wind pushing ice floes around. Yet beneath the surface, groundwater flows upward through sediments and lakebeds, carrying with it a subtle but persistent store of heat.
Saeed Memari of the Colorado School of Mines and his colleagues recently tackled this overlooked factor by integrating groundwater discharge into sophisticated hydrodynamic and ice models. Published in Water Resources Research, their study highlights how the upward seepage of groundwater—even when weak—can act like a hidden heating element. Over time, this persistent input of warmer water delays ice formation, thins existing ice, and in some cases accelerates melting.
What may sound like a gentle background process has profound implications. The study shows that the heat carried by groundwater is not evenly distributed. It clusters near shorelines, where aquifers feed into the lakes, making these areas more vulnerable to destabilized ice. This is especially important because shorelines are where human communities, critical infrastructure, and fragile ecosystems meet the frozen water surface.
Modeling Ice in a New Light
To explore these dynamics, Memari’s team tested a range of groundwater flux scenarios. At low intensities, the impact was subtle—ice formed, but a bit later and thinner than expected. With stronger fluxes, however, the changes became dramatic. Moderate groundwater flow disrupted thermal layers within the lake, making it harder for ice to stabilize. At extreme intensities, ice near the shores was not only delayed but destabilized altogether, with melting encroaching further inland and earlier in the season.
The results paint a picture of ice that is more fragile and more complex than traditional climate models suggest. In the deep centers of the lakes, the effect is buffered by sheer volume, but along coasts and shallow zones, groundwater emerges as a quiet but powerful adversary to stable ice cover.
Spatial and Seasonal Nuances
Not all groundwater is created equal, and the study emphasizes that its influence depends heavily on both space and time. Some areas of the shoreline receive much stronger groundwater pulses than others, leading to localized patches of thinning or early melt even when the rest of the lake surface remains frozen.
Seasonal timing also matters. In summer, when the surface water is already warm, groundwater adds little to the heat balance. But in winter, when surface layers are frigid, the upward seep of relatively warmer groundwater creates a stronger contrast, amplifying its destabilizing influence on ice. Over weeks and months, this small but steady effect can reshape entire sections of shoreline ice.
Climate Change and a Shifting Balance
In a warming world, the role of groundwater may become even more significant. Rising groundwater temperatures, shifting precipitation patterns, and changing aquifer recharge rates all have the potential to amplify groundwater fluxes into the Great Lakes. What was once a subtle background process may, under climate pressure, grow into a dominant driver of winter ice loss.
This has consequences far beyond the frozen surface. Ice cover in the Great Lakes influences everything from fish spawning and shoreline erosion to winter shipping routes and water quality. Thinner, less predictable ice could alter ecosystems, threaten coastal infrastructure, and weaken one of the region’s natural buffers against storm-driven waves.
Unanswered Questions Beneath the Surface
While the study sheds light on groundwater’s role, it also opens new questions. How common are the extreme flux pulses modeled in the simulations? What specific geological conditions allow such intense groundwater flows to occur? Aquifer connectivity, sediment permeability, and subsurface layering all matter, but much of this hidden world remains unmapped.
Direct measurements—such as under-ice discharge monitoring, detailed temperature profiling near lakebeds, and long-term ice thickness tracking—will be critical to confirm the scenarios proposed by models. Until then, groundwater remains a partly invisible player in the ice-climate story of the Great Lakes.
Why the Subsurface Matters
The idea that subtle groundwater warming can undermine something as vast as Great Lakes ice might feel counterintuitive. But the study’s central lesson is powerful: in large, complex systems, even quiet, background processes can accumulate into transformative forces. Just as a trickle of water can carve canyons over millennia, persistent subsurface heat can erode winter’s icy grip on freshwater lakes.
By integrating groundwater dynamics into climate and hydrodynamic models, scientists are not only improving predictions of ice behavior but also reminding us that nature’s systems are deeply interconnected. No component, no matter how hidden, can be safely ignored.
A Fragile Future for Great Lakes Ice
As winters in the Great Lakes region grow shorter and warmer, the surface ice we often take for granted may become increasingly fragile. The frozen shorelines that once seemed eternal are, in fact, the result of delicate balances between air, water, and ground. Groundwater flux—quiet, unseen, yet powerful—may prove to be one of the most important variables shaping the icy future of Lakes Michigan and Huron.
The research underscores a simple but profound truth: climate change is not just about the atmosphere. It is also about the unseen depths beneath our feet, the groundwater that flows silently through rock and soil before rising into the world’s greatest lakes. In this hidden exchange between earth and water lies a story of ice, resilience, and vulnerability—one that will shape the future of winter itself.
More information: Saeed Memari et al, Quantifying the Impact of Groundwater on Ice Formation in the Great Lakes, Water Resources Research (2025). DOI: 10.1029/2025wr040581.
