Alberta glacial melt about 3 times higher than average during heat wave, glaciologist estimates

The heat wave that scorched most of Western Canada last week accelerated the melting of alpine glaciers, a glaciologist at the University of Alberta told the Calgary Eyeopener on Tuesday.

"It's very concerning," said Jeffrey Kavanaugh, an associate professor of earth and atmospheric sciences.

In the mountains, temperatures cool down about 1 C with every 100 metres of elevation gain — but when record-breaking temperatures swept through the Rockies, even the highest alpine regions couldn't escape it.

Kavanaugh found that from June 25 to July 4, the average temperature, including night temperatures, was 17.4 C at the Bow Summit in Banff National Park. In the past 12 years, the average temperature during the same period at that weather station was 8.5 C.

"A nine or 10 degree abnormality in temperature will cause a lot more melting," said Kavanaugh.

He estimated, based on data from the Agriculture and Forestry Department of Alberta and Environment Canada, that the resulting melt from glaciers during the same 10-day period was about three times higher than normal, compared with the past 12 years.

That "pulse" of meltwater travelled from the Bow Summit to Lake Louise and then to the Bow River in Calgary, where water levels were high and fast several days later.

In other parts of the Rockies, rapid glacial melting caused flooding.

"Please be advised that with the extreme hot weather, river levels are extremely high," officials for Mount Robson Provincial Park in B.C. warned on June 30. On July 1, three hiking trails needed to be closed because of damage from flooding waters.

Important water source disappearing

As accelerated melting causes glaciers to retreat faster, that's bad news for our water supply.

"We rely on glacier flow a lot more than we realize," said Kavanaugh, explaining that when snowmelt, rainfall and snowfall are low, glaciers pick up the slack.

"Our agriculture, our industry, our populations rely quite strongly on these waters to get us through the summer," he said. "And so as we see the glaciers retreating, we're also seeing those sources of water in the summertimes retreat."

It's a point of concern for Calgary, which relies on the Bow River for nearly 60 per cent of its water, according to the city. But it's not just Calgary that is at risk when glaciers disappear; the entire watershed is affected.

"These rivers continue on to Saskatchewan and Manitoba, up to Hudson Bay," said Kavanaugh. "And so all of the communities downstream, all the industry and agriculture downstream, also rely on this water, especially during summer."

Retreating glaciers will cause 'drastic change'

A 2015 study published in Nature Geoscience predicted that 70 per cent of glaciers in Western Canada will be completely gone by 2100 — and that the fastest rate of ice loss, corresponding to higher rates of meltwater to rivers, will happen from 2020 to 2040.

"This is going to be a drastic change," said Kavanaugh. "Right now, I hate to use the word 'enjoying,' but we are enjoying an additional amount of water in the summer because these glaciers are losing their reservoirs, they're retreating.

"It's high times right now for us, but they will not last."

With files from the Calgary Eyeopener.