The Rocky Mountains conjure up images of gray rugged peaks surrounded by white. But the upper reaches of harsh mountain landscapes often bloom with a pinker hue.
Watermelon snow, also known as glacier blood, is caused by algae that turns snow a surprising shade of red.
Algae bloom in summer and occur in snowfields above glaciers, frozen lakes, rugged peaks, and icy valleys in the upper mountainous terrain.
The darker the snow, the faster it melts, and new research sheds light on the threat snow algae pose to shrinking glaciers in northwestern North America.
Snow algae researcher Lynne Quarmby, lead author of a study recently published in the journal Science Advances, said the findings serve as a warning about our changing climate.
“We don’t need any more canaries in this mine, but they are just another canary in the mine,” said Quarmby, a professor of molecular biology and biochemistry at Simon Fraser University.
“The loss of algae is an indication that we are losing snowpack and glaciers, and these will affect our survival and the survival of many other organisms.”
The study mapped the presence of snow moss in the mountains of Alaska, Idaho, Montana and Washington state, as well as Alberta, British Columbia and northern Canada.
Researchers developed a machine learning program to analyze more than 6,100 satellite images of glaciers taken between 2019 and 2022.
The study found that red-pigmented algal blooms contribute to glacier melting. But global warming poses a much greater threat to mountain glaciers and the surprisingly complex microscopic ecosystems that allow snow algae to colonize them.
“We started this study to examine the impact of climate change on these flowers and their impact on climate change,” Quarmby said.
“And I think the impact of climate change on them is clear and dramatic.”
A red survival mechanism
Supported by a broad ecosystem of bacteria and fungi, snow algae thrive when water and nutrients are released from melting snow.
This phenomenon is a consequence of flowering. Chlamydomonas nivalis, It develops at temperatures close to freezing point. Flowers that rely on photosynthesis act as carbon sinks, absorbing carbon dioxide from the atmosphere.
Closely related to the blue-green algae often seen in lakes, snow algae have a red pigment that allows them to survive in harsh mountain conditions.
“The red pigment means that when they bloom, they give the snow this red tint,” he said. “It’s called watermelon snow because it resembles the color of a watermelon.”
A hiker holds a handful of watermelon snow caused by snow algae. A new study examines the presence of blooms on glaciers in North America. (Rick Bowmer/Associated Press)
The blooms darken the surface of summer snow-covered areas, making them less reflective to the sun and causing the snowpack and ice beneath the bloom to melt more quickly.
Quarmby said the red pigment creates a “positive feedback loop”: The algae feed on water released by the added heat.
The dark hue also acts as a “shade umbrella” that protects the algae from sun damage, he said.
Quarmby and SFU researcher Casey Engstrom set out to draw a large-scale map of microscopic ecosystems.
They found that between 2019 and 2022, red snow covered 4,214 square kilometers of glacier area, accounting for 4.5 percent of the total study area.
Researchers estimate that red snow contributes an average of three centimeters of snow meltwater per season.
“Effect [the algae] “It’s real, it’s real,” Quarmby said. “But of all the things we need to worry about that are increasing climate change, that’s not the one we need to worry about.”
Snow algae was found on 4,552 of the 8,700 glaciers examined.
Some had only one patch, but most had large flowers. For example, in 2020, algae covered almost two-thirds of the surface area of Alberta’s Bow Glacier in the Wapta Ice Field.
Glaciers along the Pacific Northwest are often full of algae, but during 2020’s heat dome, the ice melted so quickly that the blooms didn’t have a chance to develop.
Quarmby said that as the snow begins to disappear due to rising temperatures, the algae will also disappear. This would mean the loss of a valuable ecosystem that scientists are just beginning to understand.
“For me, it’s just another little sadness that we’re losing it. If you see these things under a microscope, they’re magnificent. Even if you just see them in the landscape, they’re awe-inspiring.”
A hiker walks through pink-colored snow at Tony Grove Lake near Logan, Utah, on Wednesday, June 28, 2023. (Rick Bowmer/Associated Press)
Utah State University ecologist Scott Hotaling, who studies biodiversity in cold, high-altitude environments, said the scope of the research was impressive. Hotaling was not involved in the SFU study.
He said that based on satellite images, researchers were able to examine glaciers that were previously inaccessible to science and collect data on a very large scale.
Hotaling said the study provides an important basis for the impact of snow algae on retreating glaciers.
“As the snowpack decreases, these blooms will become increasingly denser and smaller and smaller.
“The melting properties of snow algae will become increasingly important. When there is only a small amount of snow left, anything that affects this is more important.”