Speaker 1: Welcome to brain stuff from how stuff works, Hey, brain stuff,
Speaker 1: Lauren Vogel bomb here. Normally snow looks white. This is
Speaker 1: because the ice crystals that make up clusters of snow
Speaker 1: reflect and scatter every color frequency in the visible light spectrum.
Speaker 1: So when sunlight bounces off of a snow bank, all
Speaker 1: those colors blend together, giving the snow a white appearance.
Speaker 1: Or at least that's what usually happens. Every so often,
Speaker 1: though mother Nature throws as a curveball with a blanket
Speaker 1: of non white snow. Plenty of the Elder was a
Speaker 1: Roman naturalist who lived from twenty three to seventy nine.
Speaker 1: In one of his books, he wrote about red tinted snow,
Speaker 1: which ancient travelers sometimes encountered. His hypothesis was that snow
Speaker 1: changes color as time goes by, like a rusting piece
Speaker 1: of iron snow itself. Plenty wrote reddens with old age,
Speaker 1: and reports of crimson colored snow kept pouring in over
Speaker 1: the next two millennia. To figure out what's really going on,
Speaker 1: we spoke via email with climates scientist Randalls Serveny. He
Speaker 1: reports people in the dark and Middle Ages were often
Speaker 1: freaked out by it. A professor at Arizona State University.
Speaker 1: Serveny dedicated an entire book to weird weather stories in
Speaker 1: two thousand five, titled Freaks of the Storm. It includes
Speaker 1: a passage on red snow. As Serveny points out, there
Speaker 1: Charles Darwin himself once came across white snow in the
Speaker 1: Andes Mountains that turned blood red as it thawed. Another
Speaker 1: important figure who witnessed the tinted precipitation was Sir John Ross,
Speaker 1: a British naval officer and Arctic explorer. A reddish or
Speaker 1: pinkish snow isn't just a historical curiosity. It's still being observed.
Speaker 1: In February, for instance, a puddle of red water that
Speaker 1: turned out to be melted vermillion snow was found in
Speaker 1: Glacier National Park. So what's the mechanism behind this? In
Speaker 1: some cases, scarlet dust may be a contributing factor. Serveny said.
Speaker 1: Many of the historic blood snows of Europe are associated
Speaker 1: with moisture mixing with red Saharan dust that's blown northward
Speaker 1: into Europe, which then falls out as either red rain
Speaker 1: or snow. But it turns out that more often than not,
Speaker 1: red snow is the product of algae and as scientists
Speaker 1: have learned recently, the stuff is also contributing to climate change.
Speaker 1: We've known for some time now that red or pink
Speaker 1: snow is generally caused by select types of green algae,
Speaker 1: including these species Clematomons novellis. These life forms live in
Speaker 1: high altitude snow fields around the world. Although they are
Speaker 1: technically green in color, the algae produce a red pigment
Speaker 1: during the warm seasons. Doing so helps protect the organisms
Speaker 1: from excessive solar radiation. We also spoke with biologist Arwin Edwards,
Speaker 1: a research fellow at everyst With University in Wales. He said,
Speaker 1: I think of the red pigment as a sunscreen. He
Speaker 1: explained the life cycle of this and related types of alga.
Speaker 1: During the winter, the organisms go dormant. Once spring arrives,
Speaker 1: they make their way toward the surface of the snow
Speaker 1: and then bloom. But in order to grow, the life
Speaker 1: forms need liquid water in the form of wet snow
Speaker 1: in order to photosynthesize. This is another reason why the
Speaker 1: red pigment is so useful. Dark colored objects absorb more
Speaker 1: heat than light colored ones. In snowy fields where Clematomonis
Speaker 1: is present, you'll find dense communities of the microorganisms. A
Speaker 1: single millimeter that's point zero three inches of snow can
Speaker 1: contain five hundred thousand of these life forms. So in
Speaker 1: a large cluster of the algae starts to release red
Speaker 1: pigment in mass, they darken the snow they're living in.
Speaker 1: As a result, the snow itself adopts a pinkish look.
Speaker 1: It also begins to melt. So is this a cause
Speaker 1: for concern? In twice sixteen, the journal Nature published a
Speaker 1: report written under the leadership of Stephanie Lutts, then a
Speaker 1: scientist at the University of Leeds. Edwards was one of
Speaker 1: her co authors. After looking at forty samples of the
Speaker 1: scarlet material from glaciers in Iceland, Norway, Greenland and Sweden,
Speaker 1: the researchers reached a harrowing conclusion. Edwards said, our paper
Speaker 1: is one of the first of several which have identified
Speaker 1: a five to fift percent acceleration of glacier melting rates
Speaker 1: as a result of algae on the glacier surface us
Speaker 1: a biological darkening effect. Put another way, glacial snow melts
Speaker 1: five to fifteen percent more rapidly when Clementomonus or similar
Speaker 1: types of algae are present, and that's not good news.
Speaker 1: University of Bristol glaciologist Alejandra Anisio was a co author
Speaker 1: on that Nature paper. Summing up the problem in an
Speaker 1: email exchange, he said, basically, because of the darker coloration
Speaker 1: of snow with the presence of the algae, the snow
Speaker 1: absorbs more of the solar radiation, which increases retention of
Speaker 1: heat and melting of the snow. The process is not
Speaker 1: insignificant and must be taken into account if we want
Speaker 1: to understand how fast glaciers and ice sheets will melt
Speaker 1: with global warming. Also, there may be a self perpetuating
Speaker 1: feedback loop at work here. The red tinted algae melts snow,
Speaker 1: which enables more of the algae to grow, which leads
Speaker 1: to even more melted snow, and so on. But let's
Speaker 1: shift gears for a moment and talk about one of
Speaker 1: the red snow's weirdest qualities. It's sent People who come
Speaker 1: across the algae laden snow sometimes report that it has
Speaker 1: a sweet watermelon like scent. For the record, Edward says
Speaker 1: he's never detected the odor himself, but that it's probably
Speaker 1: the byproduct of those red pigments. Some popular science writers
Speaker 1: have also advised against eating red snow because it has
Speaker 1: been reported to cause gastric problems, perhaps due to the
Speaker 1: algae other decaying material or mineral dusts and snow can
Speaker 1: come in other colors as well. In January eighteen, Central
Speaker 1: Kazakhstan received a layer of black tinted snow. This may
Speaker 1: have been the result of industrial pollution. Additionally, there are
Speaker 1: some types of algae that create yellowish snow. Of course,
Speaker 1: as any third grader or dog owner can tell you,
Speaker 1: that's not the only way to get yellow snow. Today's
Speaker 1: episode was written by Mark Mancini and produced by Tyler Clang.
Speaker 1: For more on this and lots of other rose tinted topics,
Speaker 1: visit our home planet, how stuff works dot com.