There’s nothing quite like seeing the iconic milky blue-green waters of Peyto Lake for the first time.
Those colours truly take your breath away.
Like many glacier-fed lakes in the Rockies, Peyto is a natural gem that locals and tourists flock to see.
The rare colour has always been reminiscent of a bright turquoise stone, but that’s slowly changing.
While the lake’s colour naturally fluctuates throughout the year, Peyto’s colour is slowly being altered permanently.
In time, it loses its cloudy, almost supernatural-looking blue-green for a deeper, clear sapphire colour.
Specific conditions cause the lake’s traditional colour.
While still beautiful, it won’t stand out quite the same way – and scientists have identified the culprit responsible for the loss.
Essentially, over millions of years, pressure from the surrounding glaciers grinds rock sediment into fine dust. When the glaciers melt each spring, the runoff flows a ton of these tiny particulates into the lake’s waters.
This rock sediment is commonly known as Glacier Milk or Glacial Flour.
When light hits these floating particles, it refracts off them – rather than passing straight through the water. This gives the lakes of the Rockies their distinct bright, creamy hue.
The freezing temperatures of the lakes from glacier water also discourage algae and bacteria growth, keeping them “cleaner” than interior lakes.
But Glacier Milk can’t exist without glaciers; unfortunately, glaciers in the Canadian Rockies are dying. Peyto Glacier is one of these dying glaciers, feeding Peyto Lake.
Peyto Glacier has shrunk by around 70 percent over the last half-century, a dramatic change highlighted in satellite imagery from NASA.
It’s expected to be almost entirely gone in a single lifetime.
As Peyto Glacier shrinks due to warming temperatures, there’s less runoff, and less glacier milk goes into Peyto Lake, so the colour changes.
This is not the only Albertan glacial lake experiencing this.
While the colour changes in Peyto Lake are subtle, other lakes like Curator Lake or Geraldine Lakes in Jasper National Park have already experienced an almost total loss of their original turquoise glow.
This happens rapidly. A lake can shift and become dark and clear in just a few years.
Janet Fischer, a biology professor with her husband, Mark Olson, who has studied and documented lake colour in the Canadian Rockies for 18 years, told CBC it’s a bit tough to watch in real-time. “I find these lakes beautiful in all their stages, but there is a sadness when you have spent your life’s work documenting a change that humans have accelerated,” she said.
“The lakes will still be beautiful. But they’ll be different.”
Watch the amazing film Losing Blue below which is a cinematic poem about losing the otherworldly blues of ancient mountain lakes, now fading due to climate change.
