The world’s largest ice skating rink is 5 miles long—but its very existence is threatened by climate change

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“Better catch up, Dad,” my daughter said as she and her brother skated into the night.

We were at the start of the Rideau Canal Skateway, part of a United Nations World Heritage Site cutting through the heart of the Canadian capital.

At 7.8 kilometers, or roughly 5 miles from end to end, the skateway is the world’s largest ice rink and one whose very existence is threatened by climate change. But on our recent visit, as the wind chill dropped to 3 degrees Fahrenheit, the ice was cold and fast.

More than 1 million people skated on the Rideau Canal Skateway in Ottawa, Ontario, this winter. [Photo: Phil McKenna/Inside Climate News]

The free public rink has attracted millions of tourists since the city began maintaining it as a skateway in 1971.

In the early years, visitors could typically count on a skating season that lasted from late December through February or early March. Recently, however, the season has been shrinking. Two years ago, in the winter of 2022-23, the skateway didn’t open at all. This year, ice on the canal bounced back, with one of its longest seasons in recent memory.

“The cold that we’ve had, it’s fantastic,” said Bruce Devine, the senior manager for facilities and programs for Canada’s National Capital Commission, which oversees the skateway. “We’re back to where we were three years ago.”

This year’s season, which hosted more than 1.1 million skaters from January 11 until it officially closed on March 10, may be an anomaly. Winters in the Ottawa region will be five weeks shorter by 2050 if global greenhouse gas emissions continue unabated, according to a report the NCC and the City of Ottawa commissioned in 2020. 

Perhaps even worse for the skateway: There would be 35% fewer “very cold” days, days below minus 10 degrees Celsius (14 degrees Fahrenheit). Water, of course, freezes at 32 degrees Fahrenheit, but intense cold of 14 degrees or below is needed for significant ice formation.

In 2022, the NCC launched a four-year study of the canal and its ice with researchers from Carleton University in Ottawa. Their aim is to figure out how to keep the skateway “open and thriving” as winters become more unpredictable.

Much of the research focuses on getting a baseline understanding of the ice and how it varies across the canal. Researchers use ice augers to drill into it, measure its thickness and collect core samples to assess its quality.

They also employ ground penetrating radar that they pull across the ice on a sled, a weather station that sits on top of the ice and sensors that are either suspended in the water column or embedded into the ice to collect a wealth of data on conditions across the skateway.

“We’re then able to . . . use that information to model the predictions of ice growth based on current weather patterns or historical weather patterns,” said Shawn Kenny, a professor in the Department of Civil and Environmental Engineering at Carleton University.

The researchers are also looking at how they can create ideal conditions for ice to grow, especially early in the season when the days are shorter and the sun is lower on the horizon. 

“Slush canons,” similar to the snow cannons used by ski resorts, can help in the early stages of ice formation. The canons spray semi-frozen water onto the canal to help crystallize a thick layer of ice on the surface.

Once an initial ice layer has formed, NCC staff use pumps to draw water from beneath the ice and discharge it on the surface. Though not a new approach, the technique speeds ice formation by exposing the water directly to cold air rather than through a layer of ice, which acts as insulation against the cold. 

Kenny and colleagues are also testing “snow bots,” lightweight, 3D-printed semiautonomous robots that can clear snow from the canal when the ice is still too thin for heavier snow-removal equipment to operate safely. If left uncleared, the snow that accumulates on the ice can further insulate the water beneath the ice and inhibit its growth.

The 2022-23 season, when the canal failed to open, had 160% more snow than the average winter. All that additional snow impeded ice formation, Kenny said.

Still, efforts the researchers are employing to enhance ice formation have their limits.

“If it’s warm, you won’t grow ice,” Kenny said.

A Provocative Idea for Rideau Canal’s Ice 

In April 2023, on the heels of the first winter in more than half a century that the skateway failed to open, a Canadian refrigeration expert floated a provocative idea.

Why not use heat pumps to pull heat from the waters of the Rideau Canal and push it into surrounding buildings, creating a thermal network that would simultaneously cool the skateway while heating surrounding homes or federal office buildings?

The idea was pitched in a blog post by Wayne Borrowman, the director of research and development for CIMCO Refrigeration, a Canadian company that claims to have built more than half of the world’s ice rinks.

Typically, indoor ice rinks vent large volumes of waste heat in the form of steam as they circulate refrigerants to draw heat out of the concrete pads beneath the ice. Some 20 years ago, CIMCO started installing new refrigeration systems that use heat pumps—a system of heat exchangers, pumps, and compressors—to harvest the waste heat. The company then used it to provide space heating to locker rooms, concession areas, and other parts of the building.

In 2019, the company deployed the concept at an outdoor ice rink in North Vancouver. Waste heat captured from the rink heats nearby buildings, the equivalent of 43 homes in all.

The nearly 5-mile-long Rideau Canal Skateway cuts through the heart of Ottawa and is part of a United Nations World Heritage Site. [Photo: Phil McKenna/Inside Climate News]

Borrowman estimated the Rideau Canal Skateway is about the size of 60 ice rinks. The canal could serve as a heat source for thousands of homes without the need to burn fossil fuels and would help cool the skateway as an added benefit, he said.

A project of such scale “may sound crazy to some, but I’ve spent my whole career involved with the design and installation of large cooling systems and I can assure you from an engineering perspective it is possible,” he wrote in 2023.

Neither CIMCO nor Borrowman have gone further with the proposal, something he recently described as a “thought experiment” driven in part by national pride.

“This is something that in our Canadian capital is a world-class event,” he said. “Where else can you skate down a canal right in the middle of a city in wintertime?”

Ice skating on canals was once a national pastime in the Netherlands, but in a warming world such activities are now largely a thing of the past. Elfstedentocht, a winter skating tour and race across the northern province of Friesland that used to draw thousands of participants hasn’t happened since 1997 due to a lack of ice.

Kenny, of Carleton University, said the thermal network Borrowman proposed is theoretically possible. But the cost for such a system, including the installation of hundreds of miles of refrigeration pipes running along the bottom and potentially sides of the canal, would likely be prohibitively expensive.

Similar cost concerns were raised about the skateway itself for more than half a century before its opening in 1971.

Kenny also noted that the canal is popular for boating in the summertime, something that could make any refrigeration pipes along the bottom of the canal prone to damage from anchor strikes.

Another option may be a more limited application of heat pumps for the most difficult to freeze sections of the skateway.

Stormwater pipes that empty into the northernmost portion of the Rideau Canal dump water that is up to 50 degrees Fahrenheit, or about 10 degrees warmer than the winter temperature of water in the canal. NCC has added pipes to divert the stormwater discharge further from the start of the skateway in recent years, but the area remains one of the last sections of the canal to freeze.

“You could install mechanical equipment such as plate and frame heat exchangers and use heat pumps to bring down that temperature so that at least you don’t have that issue of preventing the ice formation of that specific region,” said Connor Dacquay, president of EcoFease, a company based in Canada that distributes software for managing thermal energy networks. 

Dacquay said such a system would be similar to the False Creek Neighbourhood Energy Utility in Vancouver that uses waste heat captured from sewage to provide space heating and hot water to nearby buildings.

Dacquay said the system could potentially tie into an existing district energy system already operating in downtown Ottawa, which provides heating and cooling to federal buildings including Canada’s Parliament and Supreme Court.

The system could also run in reverse in the summertime, drawing heat out of buildings to cool them, while discharging the waste heat into the canal, Dacquay said.

Cole Van De Ven, an assistant professor in environmental engineering at Carleton University, said the intermittent flow rate of the stormwater runoff into the canal could make such a heat recovery system challenging from a financial standpoint. Federal and municipal permitting issues could also pose a challenge, Van De Ven said.

Installing rain gardens that slow down and reduce stormwater runoff may be a less costly solution. Such an approach would have an added benefit of removing salt, which also impedes ice formation, from the stormwater, Van De Ven added.

Skating Through Ottawa 

Visiting Ottawa during a late February cold snap, the thought of anything being too warm was hard to imagine. Despite redundant layers of insulation, including snow pants, jackets, hats, gloves, neck warmers, and thermal underwear, we still couldn’t keep out the cold. 

Initially, the frigid temperatures were manageable as a healthy tailwind and our own adrenaline propelled us south along the skateway. We glided beneath bridges, around bends, and past rest stops as kilometer markers on the side of the canal seemed to fly by.

The canal itself, the entirety of which stretches 125 miles from Ottawa to Kingston, Ontario, opened in 1832 to provide an alternative trade route for ships in what was then the British colony of Upper Canada. Prior to the canal’s opening, British ships used the St. Lawrence River, which bordered New York state and was vulnerable to attack.

Now, as U.S. President Donald Trump prepared to place tariffs on Canadian imports and mused about Canada becoming the 51st state, Canadians were again considering alternative trade routes—in the form of new oil and gas pipelines that would bypass the United States but would also fuel further warming.

Food vendors, skate rental shops, and changing rooms are stationed along the canal. [Photo: Phil McKenna/Inside Climate News]

Nearing the halfway point of the skateway, we stopped at a food truck parked on the ice. It sold a mix of Asian street food and poutine, a Canadian staple of French fries and melted cheese slathered in gravy. 

We ate quickly inside a heated changing room, determined to continue on our way. But by the time we got back outside, our bodies had cooled.

“To be totally honest, my feet are getting kind of cold,” my son said, voicing what each of us knew to be true but didn’t want to admit. 

It was time to turn around and head back to our hotel, content to know that at least for now, on a canal in Ottawa, winter persists.

—By Phil McKenna, Inside Climate News

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This article originally appeared on Inside Climate News. It is republished with permission. Sign up for its newsletter here.

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