Climate change is reshaping lake ecosystems across the northern hemisphere. New research shows that the impacts will be most severe in the Arctic, disrupting lake productivity.
Led by scientists from USA, Canada and Norway, a newly published study uses models of sunlight, ice, and snow to reveal how warming winters are disrupting lake productivity.
Lake scientists have long overlooked the ice-covered season, leaving major data gaps on how winter conditions shape lake ecosystems, and on possible impacts of change.
“The ecology of ice-covered lakes is a bit of a black box for lake scientists. For a long time, we assumed that nothing interesting happened under the ice,” explains lead author Ted Ozersky, University of Minnesota Duluth.
But as climate change shortens winters, knowledge about how lakes function under the ice have become urgent. Ice thickness, snow depth, and timing of freeze and thaw all determine how much light reaches the water, and with it the potential for photosynthesis and food web activity.
Shifts in Productivity and Food Webs
The study shows that high-latitude lakes, from northern Norway to the Canadian Arctic, are far more sensitive to winter changes than lakes farther south. At 75°N, for example, more than half of the year’s solar radiation arrives while lakes are still ice-covered. Even small shifts in ice duration or transparency can therefore trigger large ecological impacts.
“In northern Norway and in other Arctic regions, many lakes are still frozen well into the midnight sun period. In these Arctic lakes, under-ice primary production can contribute substantially to food webs and could be threatened by predicted increases in snow cover. On the other hand, less ice during continuous daylight could create favorable conditions for more open-water productivity,” says co-author Amanda Poste, Norwegian Institute for Nature Research (NINA)
As warming continues, this mismatch could narrow. More overlap between light and warmth may boost biological productivity but also reshape predator–prey relationships and the timing of food web events.
A Global Effort to Understand Frozen Lakes
“Many researchers who are starting to study frozen lakes focus on just one region. By collaborating with scientists across the northern hemisphere, from Minnesota to Québec to the high Arctic, we were able to identify this large-scale pattern,” concludes Ozersky.
The findings offer a new framework for predicting how climate change will affect lakes worldwide. The authors are now working with dozens of international partners to expand winter lake monitoring in order to understand and address future trends.
Amanda Poste and Eva Leu will follow up these questions as Norwegian partners in a recently funded Nordforsk-project, led by Milla Rautio titled: Arctic freshwater food systems: Influence of warming winters and increased snow cover (FROST, running from 2025-2029).