Snow isn’t always white; algae can make it look green, red, or orange, and scientists are trying to understand how and why these colorful patches appear.
JUANA SUMMERS, HOST:
Quick question. What color is snow? If you said white, well, of course, you’re right. But here’s something you might not know. Sometimes snow can look green or orange or red because patches of snow can be home to microscopic algae. NPR’s Nell Greenfieldboyce reports on what scientists learn when they came across one rainbow-colored snowfield in Montana’s Glacier National Park.
NELL GREENFIELDBOYCE, BYLINE: In the Western United States, snow algae most often turns snow pink. People call this watermelon snow. Trinity Hamilton is a biologist at the University of Minnesota. She says, if you were out hiking or skiing and came across this snow algae…
TRINITY HAMILTON: It would look like someone sprayed Gatorade, like a red Gatorade or Kool-Aid out on the snow surface.
GREENFIELDBOYCE: Not too long ago, though, researchers with her lab were in the Rocky Mountains and came across one spot that had not just pink snow but also patches of orange and green. Researcher Pablo Almela says this was a real surprise.
PABLO ALMELA: The thing is, after three years sampling the Rockies was the first time we found in the same snow patch the three different colors. So that’s why it was really shocking. We took the opportunity to study why they were different.
GREENFIELDBOYCE: He says it normally can be hard to directly compare different colors of snow algae from different places since snow and environmental conditions can be so varied. But here, they were all in the same setting. So the researchers collected samples for lab analysis. They also took measurements to check the impact of each color on absorbing light and heat, which can affect snow melting. Almela says he initially thought the three colors might all be the same species of algae, just at different stages of its life cycle, but no.
ALMELA: Different colors were related to different species, different communities of the snow algae blooms.
GREENFIELDBOYCE: And he says compared to the orange and green, the red color increased snow melting the most by far. He says this could help explain why red is more commonly found than other colors.
ALMELA: This color will represent an advantage because they can melt more snow, so they have more liquid water surrounding the cells.
GREENFIELDBOYCE: And the algae cells need liquid water to survive. The findings were recently published in a science journal called New Phytologist. Roman Dial, a researcher who wasn’t part of the team, says he loves these results. He’s with Alaska Pacific University and has been thinking about the colors of snow algae for a long time, ever since he first saw red snow.
ROMAN DIAL: It’s pretty amazing that the snow algae are basically the best color they could be to help produce liquid water in a frozen environment.
GREENFIELDBOYCE: With climate change, there’s now increased interest in how colorful snow algae might speed up glacier melting. Robin Kodner is with Western Washington University. She says there’s so many basic questions about snow algae that still need to be answered.
ROBIN KODNER: Like, how do the algae get there in the first place, and do they reappear in the same place from year to year? And that sort of determines, like, why you might have multiple colors on a single patch. Like, you just need to know how they get there.
GREENFIELDBOYCE: To help figure that out, she recently started something called the Living Snow Project. Volunteers help track snow algae while they’re skiing or hiking in the mountains. Over a thousand samples have been sent in so far.
Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF JOHN LEGEND SONG, “PURPLE SNOWFLAKES”)
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