Freshwater lakes around the globe are experiencing shorter freezing periods due to climate change, significantly impacting human safety, water quality, biodiversity, and the cycling of nutrients on a global scale. This information comes from a recent review conducted by an international team of researchers led by Stephanie Hampton from Carnegie Science.
A comprehensive analysis was carried out by scientists from the United States, Canada, and Sweden, marking a crucial call for more research on freshwater ecology in winter. This study is published in Science.
There are millions of freshwater lakes globally, most of which typically freeze in the winter. The researchers’ thorough review reveals a substantial change in the duration of lake ice over the past 25 years, with ice meltdowns commencing at least a month earlier than in previous centuries.
“The time that lakes are completely frozen has shortened by 31 days over the last 165 years, and many lakes that once froze every winter are now completely ice-free some years,” states Hampton. “This has significant consequences for communities globally that rely on these lakes for drinking water, recreation, fishing, and ice-road travel, in addition to their spiritual and cultural significance.”
Hampton, who serves as the Deputy Director of Carnegie Science’s Biosphere Sciences and Engineering division, is a freshwater ecologist with 18 years of experience studying microscopic plankton in Siberia’s Lake Baikal. Over the last ten years, she has expanded her focus to examine global trends concerning lake ice amid rising temperatures.
The team’s findings illustrate the ecological damage caused by reduced ice cover, affecting everything from the health of individual lakes to the intricate balance of processes that make up the Earth System.
The researchers emphasize that ecologists worldwide must begin studying lakes in winter, a season often overlooked due to safety and logistical challenges, to truly comprehend the extensive risks associated with ice loss. Their paper outlines crucial research areas that have significant implications for both human and environmental health.
According to Hampton and her collaborators, the reduced duration of ice and rising temperatures have a negative impact on biogeochemical processes and microbial activity in lakes, increasing the likelihood of water quality issues. For instance, warmer waters can lead to toxic cyanobacteria blooms, posing risks to both fish and humans. Additionally, these blooms can deplete oxygen levels, releasing trapped metals from lake sediment and introducing further concerns for water purity.
Changes in ice duration also threaten the diversity of lake ecosystems. Temperature fluctuations may benefit invasive species adapted to warmer conditions while harming cold-water fish and other organisms.
The researchers highlight the need for further investigation into how the diminishing ice cover on lakes influences the global carbon cycle. Evidence suggests that ice cover helps lakes capture carbon from the atmosphere, while warmer waters can amplify the release of greenhouse gases like methane and nitrous oxide.
Moreover, ice loss can lead to heightened evaporation of lake water, potentially decreasing freshwater access for nearby communities over time, and may also make these areas susceptible to more severe snowfall and erosion. More research is necessary to understand how lakes contribute to the water cycle in a warming climate.
“It’s increasingly clear that many lakes are freezing later and melting earlier, or experiencing both,” asserts Hampton. “Over a billion individuals live close to lakes that freeze, and these phenomena are altering how people use these resources. By analyzing our current understanding of how these changes affect lake ecosystems and surrounding communities, we have identified essential subjects that require deeper exploration. Gaining insight into the complexity and range of these threats is crucial for developing effective response strategies.”
While researchers like Hampton have studied the ecology of lakes in the Northern Hemisphere and at high elevations for many years, the investigation of lakes during winter is a relatively new area of research. Hampton and her peers are leading efforts to establish safe research methodologies for investigating iced-over conditions. Earlier this year, she and her team organized a “winter school” at Wisconsin’s Trout Lake, where early-career researchers learned how to safely collect samples from frozen water bodies.
“Looking forward, we must invest in a deeper understanding of the vital roles that lake ice plays in maintaining the health of our planet and supporting the communities that rely on these lakes,” concludes Hampton.
The Science paper’s co-authors include Ryan McClure from Carnegie Science, Stephen Powers from Baylor University, Hilary Dugan from the University of Wisconsin, Lesley Knoll from Miami University of Ohio, Bailey McMeans from the University of Toronto, Michael Meyer from the U.S. Geological Survey, Catherine O’Reilly from Illinois State University, Ted Ozersky from the University of Minnesota, Sapna Sharma from York University, David Barrett from the University of Calgary, Sudeep Chandra from the University of Nevada, Joachim Jansen and Gesa Weyhenmeyer from Uppsala University, Milla Rautio from the Université du Québec, and Xiao Yang from Southern Methodist University.
