If You See Pink Snow, This Is What It Means

This pink "watermelon snow" is a striking, bright color reminiscent of sweet summer fruit. But the cause of the snow's color change could lead to problems.

Winter brings icy white snow to the mountains each year, but recently, people have started encountering something out of the ordinary: pink snow. This unusual snow has also earned the nicknames “watermelon snow” and “glacier blood” for its rosy appearance.

While it seems “cute,” scientists are concerned about its potential environmental impact. But what causes snow to turn pink in the first place? Here’s what you need to know.

What does it mean when snow is pink?

When this rosy snow appears, it means blooming green algae called Chlamydomonas nivalis (C. nivalis) is present in the snowpack. According to Smithsonian Magazine, C. nivalis isn’t exclusive to North America. The alga blooms in mountain ranges throughout the world, and scientists have studied the photosynthetic organism for over 100 years. Watermelon snow isn’t some random, inexplicable phenomenon, and it isn’t anything new to scientists—it’s among other natural winter phenomena.

According to Scientific American, C. nivalis reacts to UV rays when exposed to the sun. This green alga requires a natural “sunscreen” to protect its chlorophyll molecules (the molecules necessary for photosynthesis, or how algae harvest light to produce their food). When the green alga is resting (or in its zygote stage), it needs protection and uses its natural carotenoids (UV-absorbing pigments) to stay safe from harsh UV rays. Those pigments cause the pink color in the snow as the C. nivalis algae concentrate on its surface through melting or evaporation.

In simple terms, the baby algae need to stay safe and enlist the help of natural biochemical sunscreen, which makes it appear orange or reddish under a microscope and creates pink snow.

Where is pink snow found?

Researchers and bystanders have commonly seen the pink-hued snow in the Western United States. Some areas where scientists scouted for pink snow in the summer of 2022 include Utah, Montana, Wyoming, Washington and Oregon. According to Wired, it also appears in Alaska.

As the snow begins to melt, the prevalent concern is that the algal blooms contribute to the West’s snowpack melt. Scott Hotaling, a professor in the Watershed Sciences Department at Utah State University, recently told KUER’s Kristine Weller, “There’s a lot of evidence now that shows that these algal blooms contribute rather significantly to overall melt of snowpack around the West.” If the snow melts at higher rates and quicker speeds, it could throw off the delicate balance of natural water supplies and stream temperatures, thus furthering drought in the U.S. West.

For now, researchers are still investigating unanswered questions linked to these algae blooms.

At least if you spot pink snow next time you’re in the mountains, you’ll know it isn’t your eyes playing tricks on you!

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Cianna Garrison
Cianna Garrison is a California-based freelance writer who covers everything from food news to tech to lifestyle. Her work has appeared in Elite Daily, How-To Geek, Review Geek, Truity, and other publications. She received her Bachelor's degree from Arizona State University in 2018. In her free time, she likes to read, write fiction and poetry, and perform in live theater.