The Rocky Mountains conjure up images of gray, rugged peaks with white peaks. But in the upper reaches of the rugged mountain landscapes, a pinker hue often blooms.
Watermelon snow, also called glacial blood, is caused by algae that gives the snow a surprising red color.
The algae bloom in summer and form on the snowfields left behind on glaciers, frozen lakes, rugged peaks and icy valleys in the upper reaches of mountain areas.
The darker the snow, the faster it melts – and new research is shedding light on the threat snow algae poses to the shrinking glaciers of northwestern North America.
Snow algae researcher Lynne Quarmby, lead author of a study recently published in Science Advances, said the findings serve as a warning about our changing climate.
“We don’t really need more canaries in this mine, but they are another canaries in the mine,” said Quarmby, a professor of molecular biology and biochemistry at Simon Fraser University.
“The loss of the algae is just an indication that we are losing snowpack and glaciers, and these will impact our lives and the lives of many other organisms.”
The study mapped the presence of snow algae on mountains in Alberta, British Columbia and northern Canada, along with the states of Alaska, Idaho, Montana and Washington.
The researchers developed a machine learning program to analyze more than 6,100 satellite images of glaciers captured between 2019 and 2022.
The research found that the red-pigmented algae blooms contribute to the melting of glaciers. However, global warming poses a much greater threat to mountain glaciers and to the surprisingly complex microscopic ecosystems that allow snow algae to colonize them.
“We started this research to look at the impact of climate change on these flowers and their impact on climate change,” says Quarmby.
“And I think the impact of climate change on them is clear and dramatic.”
A red survival mechanism
Supported by a vast ecosystem of bacteria and fungi, snow algae thrive when water and nutrients are released from melting snow.
The phenomenon is the result of flowering of Chlamydomonas nivalis, which thrives at temperatures around freezing. The flowers rely on photosynthesis and act as carbon sinks, absorbing carbon dioxide from the atmosphere.
Although closely related to the blue-green algae commonly found 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 a red tint,” she said. “It’s called watermelon snow because it resembles the color of watermelon.”
A hiker holds a handful of watermelon snow, caused by snow algae. A new study examines the presence of the flowers on glaciers in North America. (Rick Bowmer/Associated Press)
The flowers darken the surface of the summer snow fields, making them less reflective of the sun, causing the snow cover and ice under the blooms to melt more quickly.
The red pigment creates a “positive feedback loop,” Quarmby said: the algae feed on water released by the added heat.
The darker shade also acts as a “shade umbrella,” protecting the algae from sun damage, she said.
Quarmby and fellow SFU researcher Casey Engstrom wanted to draw a large-scale map of the microscopic ecosystems.
They found that between 2019 and 2022, red snow covered more than 4,214 square kilometers of glacier landscape, equivalent to 4.5 percent of the total study area.
The researchers estimate that the red snow provided an average of three centimeters of meltwater per season.
“The effect of [the algae] It’s observable, it’s real,” Quarmby said. “But of all the things we have to worry about that amplify climate change, it’s not something we have to worry about.”
Snow algae was found on 4,552 of the 8,700 glaciers examined.
Some had just a spot, but many had huge flowers. For example, in 2020, algae covered nearly two-thirds of the surface of Alberta’s Bow Glacier in the Wapta Icefield.
Glaciers along the Pacific Northwest coast are usually teeming with algae, but during the 2020 heat dome, the ice melted so quickly that the blooms didn’t have a chance to develop.
Quarmby said as the snow starts to disappear with rising temperatures, the algae will disappear too. It will mean the loss of a valuable ecosystem that scientists are only beginning to understand.
“For me, it’s still a small sadness that we’re losing it. When you see these things under the microscope, they’re spectacular. Even just seeing them in the landscape, it’s awe-inspiring.”
A hiker walks through the pink snow at Tony Grove Lake, near Logan, Utah, on Wednesday, June 28, 2023. (Rick Bowmer/Associated Press)
Scott Hotaling, a Utah State University ecologist who studies biodiversity in cold and high-altitude environments, said the scope of the research is impressive. Hotaling was not involved in the SFU investigation.
By relying on satellite images, the researchers could study glaciers that were previously inaccessible to science and collect data on a large scale, he said.
Hotaling said the work provides an important basis for the impact of snow algae on retreating glaciers.
“As the snow cover decreases, these blooms will become more and more concentrated and smaller and smaller.
“The melting properties of that snow algae will become increasingly important. When there is only a small amount of snow left, everything that affects it matters more.”