Fade to Blue: Mountain Lakes Lose Unique Color Due to Climate Change, Study Finds

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The distinctive milky turquoise color of mountain lakes follows the path of the glaciers that feed them, according to new research.

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“Many of the turquoise glacial lakes in the Canadian Rockies are clearing up,” said Rolf Vinebrooke, who studies these lakes at the University of Alberta. “They are turning more of the blue color that people consider normal lakes.”

The delicate, translucent celadon that says “alpine” to mountain lovers everywhere comes from meltwater from glaciers. Even small glaciers are huge rivers of ice that can pulverize rock into fine particles like flour, and it is those particles that stain lakes.

“Sunlight is reflected off these white particles,” said Vinebrooke, who published his finding in the latest State of the Mountains report for the Alpine Club of Canada. “Due to the scattering of light when it hits these particles, the lake turns turquoise.”

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However, glaciers have been badly affected by climate change. And not just the big ones.

“Between the 1970s and 1990s, when no one was talking about global warming, many of these smaller glaciers had already melted and disappeared.”

Vinebrooke took archival photographs of many lakes taken in the middle of the last century and compared them to modern images. Even in the black and white of the previous photographs, the change was evident.

The researchers then took sediment cores from the bottom of the lakes. Sediment cores reveal the history of a lake much like the growth layers in a tree trunk.

“We were looking for clear blue mountain lakes,” Vinebrooks said. “We found them, then we realized when we took these sediment cores that had only been a light blue color for the last two decades.

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“We found many lakes that are now clear, but only a few decades ago they were turquoise. His little glacier had melted. “

The color change did not happen everywhere, but it did happen frequently. It also seems to have happened fairly quickly.

“In the span of a few years, it changes and the lake clears,” Vinebrooke said.

He said it’s happening right now in places like Geraldine Lakes, a series of alpine lakes in Jasper National Park.

“We have several lines of evidence that show all of that quite convincingly.”

Vinebrooke said that a clear blue lake admits much more sunlight in the depths than a cloudy lake with glacial flour. That is likely to bring a very different local ecology, he said.

“The potential for that lake to be more productive increases because there is more microscopic growth of algae in those lakes.”

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But there are winners and losers.

Organisms adapted to the low light of milky waters are unlikely to survive what would be a severe new glow of ultraviolet radiation for them. The problem is especially acute due to the speed of the transition.

“If you remove that sunscreen, some organisms may not be able to tolerate that increased ultraviolet radiation. It doesn’t give organisms time to adapt. “

Vinebrooke suspects that some lakes, at least temporarily, may be “biologically impoverished,” especially since many are remote and in austere environments.

Ultimately, he said, it is one more example of climate change already working to alter familiar touchstones.

“Capture the here and now effects of global warming.”