Ice might seem suitable for a casual hockey game on the lake, but a new study from York University has revealed that appearances can be misleading. Warmer winters are not only impacting how thick ice gets and the timing of freezing and thawing, but they’re also affecting the ice’s quality, making it potentially unsafe. Researchers indicate that the unpredictable and milder winter conditions are leading to thinner layers of black ice, accompanied by thicker layers of white ice, which is unstable. The combination of these factors can create hazardous situations.
Ice might appear safe for a game of pick-up hockey on the lake, but a recent study conducted at York University reveals that this is not the case. Warming winters are affecting not only the thickness and timing of when lakes freeze and thaw, but also the quality of the ice, which can lead to unsafe conditions.
When lakes and rivers freeze, two main types of ice are formed: white ice and black ice. White ice is generally opaque, resembling snow, and contains more air bubbles and smaller ice crystals, reducing its strength and stability. In contrast, black ice is clear and dense, with larger ice crystals and fewer air pockets, making it much stronger.
“The quality of the ice is crucial due to its implications for the weight it can bear for human safety, as well as how much light can penetrate the ice to support life beneath frozen lakes,” explains York Professor Sapna Sharma.
The issue, according to lead author and York Postdoctoral Fellow Joshua Culpepper, is that erratic and warmer winter weather is leading to thinner black ice layers alongside thicker white ice layers, which are not stable. Together, these conditions can pose significant risks for skaters, hockey enthusiasts, snowmobilers, ice fishermen, and those driving on ice.
“We’ve observed that in general, lake ice is forming later in the season and melting earlier, indicating a shorter ice cover period. Our study focused on the nature of the ice itself and how it is changing. There may be times when individuals are on the ice thinking it is safe, but in reality, it may not be thick enough due to changes in quality,” says Culpepper.
10 cm is no longer the safe standard
Simply measuring thickness is not a reliable way to assess ice safety anymore. If there’s too much white ice and not enough black ice, the ice may lack the strength required to support a person’s weight. This scenario is what the researchers deem a “dangerous combination.”
“To skate or play on the ice, it typically requires about 10 centimeters or four inches of black ice. However, our findings suggest that climate change is leading to a prevalence of white ice conditions,” Sharma advises. She recommends that if there’s only a thin layer of black ice, individuals should double the usual thickness requirement to at least 20 cm.
“Black ice is clear and free of slush; you should avoid slushy areas,” Sharma warns, emphasizing that it’s always safer to go out on the ice with a companion or group.
Walking on thin ice
The disregard for the quality of ice is already resulting in tragic incidents. Last December in Canada, six individuals, including several teenagers in Ontario, tragically drowned after falling through thin ice. Two more fatalities occurred in Ontario in February. In Finland, four people died in similar circumstances during January and February, with an annual average of about 18 deaths. Sweden reported 16 drownings due to ice falls in 2014 and at least nine in 2021, for instance.
A 2020 study led by Sharma revealed extensive drowning incidents across the Northern Hemisphere, with a surprising number of drownings per capita occurring in northern Canada despite its cold climate.
This is attributed to rapid changes in the Arctic, which is warming four times quicker than other regions of the planet. Hence, changes in ice conditions are being felt in both southern and far northern areas, traditionally recognized as extremely cold and icy places, according to Sharma.
For transport trucks, about 100 cm or roughly 42 inches of black ice is necessary. Unfortunately, these benchmarks for transporting goods are becoming less accurate due to increased amounts of white ice, which is about half as strong as black ice. The prediction suggests a potential 95 to 99 percent loss of infrastructural support for winter ice road transportation, unless significant ice safety adaptations are implemented.
This could place remote communities at risk of being isolated and unable to obtain food, essential supplies, and medicines in winter months.
Unexpected winter weather patterns
In conducting this study, Culpepper and his co-authors were forced to halt ice measurements in mid-February on Lake Simcoe and early March on Paint Lake because the ice was dangerously thin.
Changes in precipitation due to unusually warm weather are a significant contributor to unsafe ice conditions and unpredictability. Warmer temperatures mixed with rainfall and even snow can significantly impact the structure and thickness of lake ice.
Sharma and Culpepper advise checking weather reports from the past month.
“Lake ice remembers,” says Sharma. “All fluctuations in weather are retained within the ice. If temperatures rise above 0°C for even a short time, or there are rains or unusually sunny conditions, those can affect the ice’s safety for human use. Variations of freeze and thaw cycles or temperatures above freezing weaken the ice and lead to a decrease in structural stability.”
Life beneath the ice
Declining ice quality is also having an impact on aquatic life, limiting nutrients available for fish and invertebrates, as well as phytoplankton, which require light for photosynthesis. Increased white ice hampers light penetration, adversely affecting the health of these ecosystems.
However, as Culpepper highlights, their study is among the few examining lake ice quality, which is changing dramatically. “What struck me initially was the surprising lack of comprehensive data on ice quality,” he remarks. “We had to sift through the available information and found it challenging to gather reliable data regarding ice conditions across the Northern Hemisphere.”
He emphasizes the necessity for ongoing measurements of ice quality, including thickness assessments of both black and white ice throughout the Northern Hemisphere.
The paper titled Lake ice quality in a warming world was published today in the journal Nature Reviews Earth and Environment.
