Ice might appear inviting for a pick-up hockey game on the lake, but a recent study from York University highlights that appearances can be misleading. Increasingly warm winters are not just impacting how thick the ice gets and when lakes freeze or thaw; they also affect the quality of the ice, rendering it potentially unstable and hazardous. According to researchers, the erratic and heated winter climate is resulting in thinner layers of black ice alongside thicker layers of white ice, which is the more unstable type. The combination of these two can create hazardous skating conditions.
Ice might seem safe for a spontaneous hockey game on the lake, but new research from York University suggests that this is not the case. Warmer winters are influencing not only the thickness and timing of ice formation and melt but also its quality, making the ice possibly unstable and dangerous.
When bodies of water freeze, two main types of ice form: white ice and black ice. White ice appears cloudy like snow and is filled with many air bubbles and small ice crystals, which reduces its overall strength and stability. In contrast, black ice is clear and dense, containing fewer air pockets and larger ice crystals, making it significantly stronger.
“The quality of ice is crucial because it directly impacts how much weight it can safely support for human activities and how much light can penetrate the ice for the aquatic life beneath it,” explains York Professor Sapna Sharma.
Lead author and York Postdoctoral Fellow Joshua Culpepper points out that the unpredictable and warmer winter weather is producing thinner layers of black ice and, at times, a thicker layer of white ice, which is less stable. This combination can result in dangerous settings for skaters, hockey players, snowmobilers, ice fishers, and transport trucks moving across ice.
“We know that, generally, lake ice is forming later in the season and melting sooner, indicating a shorter ice cover duration overall. However, our research focused on how the ice behaves. How is it changing? There might be times when individuals feel safe on the ice, but it could actually be unsuitable because of its insufficient thickness and quality,” states Culpepper.
10 cm is no longer a safe guideline
Simply measuring thickness is not a reliable way to assess safe ice conditions anymore. An excess of white ice paired with insufficient black ice can make the ice too weak to support a person. Researchers refer to this scenario as a hazardous combination.
“For a person to skate or play on the ice, about 10 centimeters (or four inches) of black ice is necessary, but we observe that climate change is resulting in an increase of white ice conditions,” says Sharma, who advises that if you find only a thin layer of black ice, you should double the typical recommended minimum to at least 20 cm.
“Black ice is transparent and lacks slush. It’s important to avoid walking over slushy areas,” Sharma adds, emphasizing that it’s always better to venture onto the ice with others.
In precarious situations
A disregard for ice quality has already resulted in fatalities. For example, six individuals, including some teenagers from Ontario, died within a week last December after falling through thin ice. This was followed by two more deaths in Ontario this February. In Finland, four people lost their lives to weak ice in January and February alone, with an average of 18 casualties per year. In Sweden, 16 people drowned after breaking through ice in 2014, and at least nine did the same in 2021.
A 2020 study led by Sharma revealed widespread drowning incidents across the Northern Hemisphere, with northern Canada experiencing the highest per capita death rates despite being the coldest region.
“The dramatic warming in the Arctic, which is occurring at four times the global average, causes changes in ice conditions not only in southern regions but also in the far north, which one might assume to be permanently icy,” notes Sharma.
“To support a transport truck, approximately 100 centimeters (around 42 inches) of black ice is required. So, traditional benchmarks for safe transport are no longer valid as there is an increasing prevalence of white ice, which has less than half the strength of black ice. Our projections suggest a 95 to 99 percent loss in winter ice road transportation infrastructure unless there are significant improvements in ice safety protocols.”
This shift could threaten remote communities, potentially isolating them and restricting access to essential goods, supplies, and medical services during winter months.
Unusual winter conditions
For this study, Culpepper along with his colleagues had to cease ice measurements in mid-February on Lake Simcoe and in early March on Paint Lake due to dangerously thin ice cover.
Variations in precipitation due to warmer weather are significant contributors to the unsafe ice conditions and unpredictability. Rising temperatures, rainfall, and even snow can affect both the thickness and the strength of lake ice.
Sharma and Culpepper recommend keeping an eye on weather patterns for at least the previous month.
“Lake ice records past weather conditions,” Sharma explains. “All fluctuations are preserved in the ice. If temperatures exceeded 0 degrees Celsius for any period, if there was rainfall, or if conditions were exceptionally sunny, all of this impacts the safety of the ice for human activity. When there are freeze-thaw cycles or temperatures above 0 degrees Celsius, ice becomes weaker and structurally less reliable.”
Effects beneath the surface
The decline in ice quality also disrupts ecosystems underneath as it affects the availability of nutrients for fish, invertebrates, and phytoplankton, which rely on light for photosynthesis. With an increase in white ice, less light penetrates, weakening the overall health of these ecosystems.
Culpepper mentions that their research is among the few to examine the quality of lake ice, and acknowledges the significant changes occurring in that environment. “What surprised me the most was the glaring lack of broad data on ice quality,” he shares. “We attempted to work with the limited data available across the Northern Hemisphere, but finding comprehensive and reliable information was quite difficult.”
He suggests that regular assessments of ice quality, including measuring both black and white ice thickness, across the Northern Hemisphere are essential.
The publication titled “Lake ice quality in a warming world” was released today in the journal Nature Reviews Earth and Environment.
