How do you freeze the world's largest skating rink?

How do you freeze the world's largest skating rink?

That's the question scientists in Ottawa are trying to answer as climate change brings warmer winters to the nation's capital.

Last year, the Rideau Canal Skateway had its shortest season in a decade — only 29 days — and researchers predict that trend will continue as deep freeze cycles continue to shorten.

Researchers from Carleton University are working with the National Capital Commission (NCC) to test some new ideas over the next four years to try to extend the period of time it's safe to skate on the 7.8-kilometre rink.

One of the innovations being tested is the "slush cannon," a machine that shoots water into the air so it falls to the canal as slush, coating the top layer of ice. Researchers hope the machine will act as a catalyst to speed up the freezing process.

NCC facilities manager Bruce Devine told CBC's Ottawa Morning during a recent interview that the machine works best at temperatures below –3 C.

"To open the season, we need to reach 12 inches or 30 centimetres," Devine said "We use [the slush cannon] just to initiate the ice buildup to certain inches — just enough so the ice building team can start walking on it and flood the ice as per our normal practices."

It's still being tested, but Devine said the machine, which is currently stationed near the National Arts Centre, "looks promising" and could eventually help the NCC open the skateway before New Year's Eve.

Researchers will also test a "thermosyphon," which is used to cool down the water below the top layer of ice. The machine draws heat from the water and releases it into the air above.

The hope is that these innovations will help the NCC combat the impacts of climate change on the skateway, allowing people in Ottawa to get out on the ice sooner.