What Is Red Snow?

of non white snow. Plenty of the Elder was a Roman naturalist who lived from twenty three to seventy nine. In one of his books, he wrote about red tinted snow, which ancient travelers sometimes encountered. His hypothesis was that snow changes color as time goes by, like a rusting piece of iron snow itself. Plenty wrote reddens with old age, and reports of crimson colored snow kept pouring in over the next two millennia. To figure out what's really going on,

we spoke via email with climates scientist Randalls Serveny. He reports people in the dark and Middle Ages were often freaked out by it. A professor at Arizona State University. Serveny dedicated an entire book to weird weather stories in two thousand five, titled Freaks of the Storm. It includes a passage on red snow. As Serveny points out, there Charles Darwin himself once came across white snow in the

Andes Mountains that turned blood red as it thawed. Another important figure who witnessed the tinted precipitation was Sir John Ross, a British naval officer and Arctic explorer. A reddish or pinkish snow isn't just a historical curiosity. It's still being observed. In February, for instance, a puddle of red water that turned out to be melted vermillion snow was found in Glacier National Park. So what's the mechanism behind this? In

some cases, scarlet dust may be a contributing factor. Serveny said. Many of the historic blood snows of Europe are associated with moisture mixing with red Saharan dust that's blown northward into Europe, which then falls out as either red rain or snow. But it turns out that more often than not, red snow is the product of algae and as scientists have learned recently, the stuff is also contributing to climate change.

We've known for some time now that red or pink snow is generally caused by select types of green algae, including these species Clematomons novellis. These life forms live in high altitude snow fields around the world. Although they are technically green in color, the algae produce a red pigment during the warm seasons. Doing so helps protect the organisms from excessive solar radiation. We also spoke with biologist Arwin Edwards, a research fellow at everyst With University in Wales. He said,

I think of the red pigment as a sunscreen. He explained the life cycle of this and related types of alga. During the winter, the organisms go dormant. Once spring arrives, they make their way toward the surface of the snow and then bloom. But in order to grow, the life forms need liquid water in the form of wet snow in order to photosynthesize. This is another reason why the red pigment is so useful. Dark colored objects absorb more

heat than light colored ones. In snowy fields where Clematomonis is present, you'll find dense communities of the microorganisms. A single millimeter that's point zero three inches of snow can contain five hundred thousand of these life forms. So in a large cluster of the algae starts to release red pigment in mass, they darken the snow they're living in. As a result, the snow itself adopts a pinkish look. It also begins to melt. So is this a cause

for concern? In twice sixteen, the journal Nature published a report written under the leadership of Stephanie Lutts, then a scientist at the University of Leeds. Edwards was one of her co authors. After looking at forty samples of the scarlet material from glaciers in Iceland, Norway, Greenland and Sweden,

the researchers reached a harrowing conclusion. Edwards said, our paper is one of the first of several which have identified a five to fift percent acceleration of glacier melting rates as a result of algae on the glacier surface us a biological darkening effect. Put another way, glacial snow melts five to fifteen percent more rapidly when Clementomonus or similar types of algae are present, and that's not good news. University of Bristol glaciologist Alejandra Anisio was a co author

on that Nature paper. Summing up the problem in an email exchange, he said, basically, because of the darker coloration of snow with the presence of the algae, the snow absorbs more of the solar radiation, which increases retention of heat and melting of the snow. The process is not insignificant and must be taken into account if we want to understand how fast glaciers and ice sheets will melt with global warming. Also, there may be a self perpetuating

feedback loop at work here. The red tinted algae melts snow, which enables more of the algae to grow, which leads to even more melted snow, and so on. But let's shift gears for a moment and talk about one of the red snow's weirdest qualities. It's sent People who come across the algae laden snow sometimes report that it has a sweet watermelon like scent. For the record, Edward says he's never detected the odor himself, but that it's probably

the byproduct of those red pigments. Some popular science writers have also advised against eating red snow because it has been reported to cause gastric problems, perhaps due to the algae other decaying material or mineral dusts and snow can come in other colors as well. In January eighteen, Central Kazakhstan received a layer of black tinted snow. This may have been the result of industrial pollution. Additionally, there are

some types of algae that create yellowish snow. Of course, as any third grader or dog owner can tell you, that's not the only way to get yellow snow. Today's episode was written by Mark Mancini and produced by Tyler Clang. For more on this and lots of other rose tinted topics, visit our home planet, how stuff works dot com.