As winters become milder and lake ice less stable, more children and young adults are falling through the ice and fatally drowning, say York University researchers.

A new study, which looked at 4,000 drownings in 10 countries, including Canada, Russia, Finland, Germany, Sweden and the United States, found warming winter air temperatures were a good predictor of the number of drownings. The research examined several decades of data, including 30 years worth for each province and territory in Canada.

For some countries, the number of winter drownings through ice represented 15 to 50 per cent of the total annual number of drownings. Canada had the highest number of winter drownings and the territories, where people use frozen lakes more for their livelihood, such as hunting and fishing, had the highest number of drownings per capita in all of the regions analyzed in 10 countries.

“The time when the risk of drowning is greatest is at the beginning and the end of winter, which also corresponds to the weakest ice, when it is less stable and less thick,” says lead researcher Associate Professor Sapna Sharma of the Faculty of Science, who worked with Postdoctoral Fellows Kevin Blagrave and Simon Watson, former PhD student Tessa Clemens, and an international group of scientists.

“In this study, we also looked at who was drowning, when, and what kind of activities they were doing at the time,” says Sharma. “Almost 50 per cent of drowning victims are children less than nine years old playing on the ice, while the majority of victims drowning while in vehicles, such as snowmobiles, are young adults less than 24 years old.”

The complex nature of changing winters – warming temperatures, rain on snow, and freeze-thaw events – is destabilizing the ice on freshwater lakes and rivers in countries across the Northern Hemisphere.

When winter air temperatures reached between -10C and -5C, drownings rose substantially. Once winter air temperatures closed in on 0C, the number of drowning was up to five times higher than usual. Once air temperatures reached 0C or higher, the number of drownings fell drastically, likely because the ice was visibly unsafe or non-existent.

The researchers gathered drowning records from coroners’ offices, police stations and lifesaving societies around the world, including the Lifesaving Society Canada. They also collected temperature and precipitation data for each month and area for each drowning using the data from the University of East Anglia’s Climatic Research Unit and collected population data from across Canada, Estonia, Germany, Latvia, Finland, Russia and Sweden, for regions of Italy and Japan, and from 14 states in the U.S.

“Because we also examine trends in lake ice over hundreds of years, we know that ice-on is much later in the season and ice-off is much earlier. We are seeing these trends in lakes and rivers across the Northern Hemisphere and we found that the highest number of drowning events correspond to these times of ice-off and ice-on,” says Sharma. “Lake ice is important as we have strong traditions for going out on the ice to skate or ice fish, and for some, it’s important for survival, such as through the construction of ice roads in northern communities that are the only way to get resources in the winter.”

The researchers found, however, that in those countries that have strong regulations about who can go on the ice, when, and for what activity, such as Italy and Germany, they have low incidences of winter drownings. Sharma suggests incorporating winter ice safety in swimming lessons for children.

“The climate is changing and it’s affecting when you can be on the ice safely. Individuals need to take that into account, especially this winter when more individuals will be out enjoying winter ice activities,” says Sharma. “Times have changed, and climate has changed. Winters are among the fastest warming season, especially in Northern countries, and we’re seeing the impacts of that on our lakes, and it’s also contributing to tragedies each winter.”

The paper, “Increased winter drownings in ice-covered regions with warmer winters,” was published Nov. 18 in the journal PLOS One.

Watch a video on the research below.

Precision matters. York University Distinguished Research Professor Eric Hessels, who has conducted the most precise measurement to date of the fine structure of helium and of the hydrogen n=2 Lamb shift to come closest to solving the proton-size puzzle, deals in precision every day. It is his work in the precision measurement field that has earned him the 2020 Canadian Association of Physicists (CAP) Medal for Lifetime Achievement in Physics.

It is the first time in the association’s history, since the award began in 1956, that it has gone to a York Department of Physics and Astronomy professor. The annual medal awards researchers for their distinguished service to physics over an extended time or a recent outstanding achievement. Hessels fits both categories.

“We could not be more delighted or more proud that Dr. Hessels will receive this prestigious honour for his lifetime of dedication to research in physics,” said Faculty of Science Dean Rui Wang. “Dr. Hessels’ work has far-reaching consequences for our understanding of the laws of physics and may help answer some of the unresolved fundamental questions of the universe. His impact at York University and within our faculty has been enormous, as is the imprint his research will leave on the discipline of physics.”

Hessels, renowned for his work in atomic, molecular and optical physics, is a master at developing novel and sophisticated laser and microwave experiments to ascertain the properties of atoms and nuclei, such as the dual charge exchange method and the frequency offset separated oscillatory fields (FOSOF) technique. The first method made antihydrogen atoms cold enough to trap and study, while the FOSOF technique was used to measure the radius of a proton.

“Professor Hessels specializes in precision measurement to test fundamental theories of physics. His work is important in advancing our understanding of nature and how it works,” says the Chair of the Department of Physics and Astronomy, Patrick Hall. “His research group provides invaluable opportunities for graduate and undergraduate students and postdoctoral fellows at York to be involved in cutting-edge science.”

His most recent research involves measuring the electron electric dipole moment using polar molecules frozen into a cryogenic argon solid, which could help explain why there is an abundance of matter, but very little anti-matter in our universe. He is leading a collaboration of 19 physicists and chemists working on this measurement.

“I am very honoured to receive this award,” says Hessels. “I would like to acknowledge the hard work and intelligence of my students and collaborators, as the work being honoured here would not have been possible without them.”

A professor at York since 1992, Hessels has won several prestigious awards over the years, including The John Charles Polanyi Prize, the Herzberg Medal, and the U.S. National Institute of Standards, Technology Precision Measurements Award and two Canada Research Chairs.

Hessels will deliver a plenary medal talk in the coming months, which will be posted to the CAP website.