What the decline of mountain snow cover means for Canada

The Prairies Climate Change Project is a joint initiative between CBC Edmonton and CBC Saskatchewan that focuses on weather and our changing climate. Meteorologist Christy Climenhaga brings her expert voice to the conversation to help explain weather phenomena and climate change and how they impact everyday life.

This winter brought a healthy snowpack to many mountain peaks in North America. 

California experienced record snow, at times burying communities and ski hills and in Canada, skiers and snowboarders enjoyed the powder this season, with British Columbia experiencing a flush of late-season snow putting snowpacks right around normal.

But despite this snowy winter in the mountains, climate change is taking its toll on our slopes.

So how is our mountain snow changing, what can we expect going forward, and what does that mean for our water supply?

Global trends in snow

Claudia Notarnicola is a researcher with Eurac, a private research centre based in Italy. She has studied how mountain snowpacks across the globe have changed over the past 40 years. 

Notarnicola said that in her research, which examined mountain snow cover between 1982 and 2020, there were wild swings in snow year-to-year, but a clear long-term trend.

"There is a general decrease, but the variability is very high," she said when talking about snow cover of global mountain ranges. 

Notarnicola's research shows a decrease of around 3.6 per cent in yearly snow cover, and an average drop in 15 days for snow cover duration globally. 

Though North America showed high variability, with pockets of increased snowfall at lower elevations, the overall picture is dominated by snow cover decline and a delayed start in the season with an earlier spring melt. 

"There is a correlation between snow coverage and snow coverage duration, but I'd say the duration seems to be more affected," she said.

But the decline goes beyond the past 40 years. 

Snow in the Canadian Rockies

John Pomeroy, Canada Research Chair in water resources and climate change at the University of Saskatchewan, says the snow-cover period in the Canadian Rockies has declined by anywhere from four to six weeks since the early 1970s.

This decline is in part due to faster snow melts in the spring and warmer falls, but is also affected by lower snowpack levels. 

While snowpacks are harder to keep track of accurately as they require in-person surveying, Pomery says that in the regions he has studied, there are noticeable trends, including in the Kananaskis Valley. 

"Our higher elevation snowpacks were holding, and even our middle elevation snowpacks were holding. But at the lowest valley bottom, we do have much less snow than we used to," he said. 

That stability at high elevations is thanks in part to Canada's colder climate, which is different from what is experienced in the United States or the Alps, according to Pomeroy.

"[There] the higher elevations are affected by climate warming in terms of melting the snow, earlier or causing less snow over the winter, but we haven't seen that at all in the Canadian Rockies yet."

And with shorter winters set to continue, Pomeroy says the ripple effects will become more pronounced in Alberta's mountains. 

"We see shorter and shorter snow seasons and less than half of the current snowpack in the valley bottoms going forward, virtually none in some years," he said. 

"In the middle elevations we see a fairly large drop in snowpack dropping to about half, but at the highest elevations there's a shorter snow season, but the peak snowpack is about the same."

Implications downstream

Despite more stability on the Canadian Rockies' highest peaks, our shifts in mountain snow will have an effect on those relying on that water. 

Pomeroy says the eastern slopes are critical for water supply for cities, irrigation, hydroelectric power and for the ecosystem. 

Going forward Pomeroy says shorter seasons will mean a shift in timing for prairie river flows from the peak in June to late in April or even early May. 

Those rivers will also face a lot of variability, with higher streamflows in the winter and early spring with lower stream flows without glacier support in the hot and dry summers.

"The snowpack acted as a reliable reservoir to hold water and release it even in the hot dry years and the glacier is very much the same feature," he said.

"As we lose glaciers and lose some of our low elevation snowpack, we lose the dampening of stream flow that we've had and the reliability that it will always peak in the spring and drop off in the summer."

"We have quite a few decades of very serious problems ahead of us no matter what we do and we're going to have to manage our waters very sensibly to achieve any kind of water sustainability," he said. 

Pomeroy said that this management can include using water more efficiently and storing water that flushes into the system earlier to use during irrigation later on.

Our planet is changing. So is our journalism. This story is part of a CBC News initiative entitled "Our Changing Planet" to show and explain the effects of climate change. Keep up with the latest news on our Climate and Environment page.