WEBVTT - What Is Red Snow? 0:00:02.040 --> 0:00:07.040 Welcome to brain stuff from how stuff works, Hey, brain stuff, 0:00:07.080 --> 0:00:11.520 Lauren Vogel bomb here. Normally snow looks white. This is 0:00:11.560 --> 0:00:14.080 because the ice crystals that make up clusters of snow 0:00:14.120 --> 0:00:18.120 reflect and scatter every color frequency in the visible light spectrum. 0:00:18.160 --> 0:00:20.680 So when sunlight bounces off of a snow bank, all 0:00:20.680 --> 0:00:23.920 those colors blend together, giving the snow a white appearance. 0:00:24.520 --> 0:00:27.960 Or at least that's what usually happens. Every so often, 0:00:28.000 --> 0:00:30.560 though mother Nature throws as a curveball with a blanket 0:00:30.600 --> 0:00:33.920 of non white snow. Plenty of the Elder was a 0:00:34.000 --> 0:00:37.000 Roman naturalist who lived from twenty three to seventy nine. 0:00:38.040 --> 0:00:40.520 In one of his books, he wrote about red tinted snow, 0:00:40.800 --> 0:00:44.800 which ancient travelers sometimes encountered. His hypothesis was that snow 0:00:44.880 --> 0:00:47.560 changes color as time goes by, like a rusting piece 0:00:47.600 --> 0:00:51.440 of iron snow itself. Plenty wrote reddens with old age, 0:00:52.760 --> 0:00:55.320 and reports of crimson colored snow kept pouring in over 0:00:55.320 --> 0:00:58.240 the next two millennia. To figure out what's really going on, 0:00:58.360 --> 0:01:01.720 we spoke via email with climates scientist Randalls Serveny. He 0:01:01.800 --> 0:01:04.640 reports people in the dark and Middle Ages were often 0:01:04.640 --> 0:01:07.920 freaked out by it. A professor at Arizona State University. 0:01:08.000 --> 0:01:10.959 Serveny dedicated an entire book to weird weather stories in 0:01:11.000 --> 0:01:14.360 two thousand five, titled Freaks of the Storm. It includes 0:01:14.400 --> 0:01:17.760 a passage on red snow. As Serveny points out, there 0:01:18.000 --> 0:01:20.600 Charles Darwin himself once came across white snow in the 0:01:20.680 --> 0:01:23.839 Andes Mountains that turned blood red as it thawed. Another 0:01:23.880 --> 0:01:27.440 important figure who witnessed the tinted precipitation was Sir John Ross, 0:01:27.480 --> 0:01:31.240 a British naval officer and Arctic explorer. A reddish or 0:01:31.280 --> 0:01:35.120 pinkish snow isn't just a historical curiosity. It's still being observed. 0:01:35.600 --> 0:01:38.800 In February, for instance, a puddle of red water that 0:01:38.920 --> 0:01:42.039 turned out to be melted vermillion snow was found in 0:01:42.080 --> 0:01:46.960 Glacier National Park. So what's the mechanism behind this? In 0:01:47.000 --> 0:01:51.200 some cases, scarlet dust may be a contributing factor. Serveny said. 0:01:51.560 --> 0:01:54.440 Many of the historic blood snows of Europe are associated 0:01:54.480 --> 0:01:57.880 with moisture mixing with red Saharan dust that's blown northward 0:01:57.920 --> 0:02:00.680 into Europe, which then falls out as either red rain 0:02:00.840 --> 0:02:04.000 or snow. But it turns out that more often than not, 0:02:04.520 --> 0:02:08.359 red snow is the product of algae and as scientists 0:02:08.360 --> 0:02:11.880 have learned recently, the stuff is also contributing to climate change. 0:02:12.919 --> 0:02:14.959 We've known for some time now that red or pink 0:02:15.000 --> 0:02:17.920 snow is generally caused by select types of green algae, 0:02:18.000 --> 0:02:22.120 including these species Clematomons novellis. These life forms live in 0:02:22.240 --> 0:02:25.280 high altitude snow fields around the world. Although they are 0:02:25.320 --> 0:02:28.400 technically green in color, the algae produce a red pigment 0:02:28.520 --> 0:02:31.760 during the warm seasons. Doing so helps protect the organisms 0:02:31.760 --> 0:02:36.360 from excessive solar radiation. We also spoke with biologist Arwin Edwards, 0:02:36.400 --> 0:02:40.000 a research fellow at everyst With University in Wales. He said, 0:02:40.360 --> 0:02:43.160 I think of the red pigment as a sunscreen. He 0:02:43.240 --> 0:02:46.560 explained the life cycle of this and related types of alga. 0:02:46.919 --> 0:02:50.120 During the winter, the organisms go dormant. Once spring arrives, 0:02:50.160 --> 0:02:52.120 they make their way toward the surface of the snow 0:02:52.160 --> 0:02:55.160 and then bloom. But in order to grow, the life 0:02:55.160 --> 0:02:57.720 forms need liquid water in the form of wet snow 0:02:57.760 --> 0:03:00.840 in order to photosynthesize. This is another reason why the 0:03:00.880 --> 0:03:04.720 red pigment is so useful. Dark colored objects absorb more 0:03:04.800 --> 0:03:08.240 heat than light colored ones. In snowy fields where Clematomonis 0:03:08.280 --> 0:03:11.560 is present, you'll find dense communities of the microorganisms. A 0:03:11.639 --> 0:03:14.760 single millimeter that's point zero three inches of snow can 0:03:14.800 --> 0:03:18.040 contain five hundred thousand of these life forms. So in 0:03:18.080 --> 0:03:20.400 a large cluster of the algae starts to release red 0:03:20.400 --> 0:03:23.200 pigment in mass, they darken the snow they're living in. 0:03:23.600 --> 0:03:26.360 As a result, the snow itself adopts a pinkish look. 0:03:26.960 --> 0:03:30.800 It also begins to melt. So is this a cause 0:03:30.800 --> 0:03:34.600 for concern? In twice sixteen, the journal Nature published a 0:03:34.639 --> 0:03:37.400 report written under the leadership of Stephanie Lutts, then a 0:03:37.480 --> 0:03:40.440 scientist at the University of Leeds. Edwards was one of 0:03:40.440 --> 0:03:43.200 her co authors. After looking at forty samples of the 0:03:43.200 --> 0:03:47.080 scarlet material from glaciers in Iceland, Norway, Greenland and Sweden, 0:03:47.360 --> 0:03:52.000 the researchers reached a harrowing conclusion. Edwards said, our paper 0:03:52.120 --> 0:03:54.160 is one of the first of several which have identified 0:03:54.200 --> 0:03:57.600 a five to fift percent acceleration of glacier melting rates 0:03:57.760 --> 0:04:00.440 as a result of algae on the glacier surface us 0:04:00.480 --> 0:04:05.160 a biological darkening effect. Put another way, glacial snow melts 0:04:05.240 --> 0:04:08.760 five to fifteen percent more rapidly when Clementomonus or similar 0:04:08.800 --> 0:04:11.880 types of algae are present, and that's not good news. 0:04:12.880 --> 0:04:16.880 University of Bristol glaciologist Alejandra Anisio was a co author 0:04:16.920 --> 0:04:20.520 on that Nature paper. Summing up the problem in an 0:04:20.520 --> 0:04:24.479 email exchange, he said, basically, because of the darker coloration 0:04:24.520 --> 0:04:26.919 of snow with the presence of the algae, the snow 0:04:26.960 --> 0:04:30.279 absorbs more of the solar radiation, which increases retention of 0:04:30.320 --> 0:04:33.240 heat and melting of the snow. The process is not 0:04:33.360 --> 0:04:36.080 insignificant and must be taken into account if we want 0:04:36.120 --> 0:04:38.880 to understand how fast glaciers and ice sheets will melt 0:04:38.960 --> 0:04:42.920 with global warming. Also, there may be a self perpetuating 0:04:42.920 --> 0:04:46.400 feedback loop at work here. The red tinted algae melts snow, 0:04:46.560 --> 0:04:48.960 which enables more of the algae to grow, which leads 0:04:49.000 --> 0:04:53.320 to even more melted snow, and so on. But let's 0:04:53.400 --> 0:04:55.520 shift gears for a moment and talk about one of 0:04:55.560 --> 0:04:59.600 the red snow's weirdest qualities. It's sent People who come 0:04:59.600 --> 0:05:02.480 across the algae laden snow sometimes report that it has 0:05:02.520 --> 0:05:06.279 a sweet watermelon like scent. For the record, Edward says 0:05:06.320 --> 0:05:09.279 he's never detected the odor himself, but that it's probably 0:05:09.320 --> 0:05:12.760 the byproduct of those red pigments. Some popular science writers 0:05:12.800 --> 0:05:15.280 have also advised against eating red snow because it has 0:05:15.320 --> 0:05:18.640 been reported to cause gastric problems, perhaps due to the 0:05:18.720 --> 0:05:23.240 algae other decaying material or mineral dusts and snow can 0:05:23.320 --> 0:05:26.719 come in other colors as well. In January eighteen, Central 0:05:26.800 --> 0:05:30.240 Kazakhstan received a layer of black tinted snow. This may 0:05:30.240 --> 0:05:33.360 have been the result of industrial pollution. Additionally, there are 0:05:33.360 --> 0:05:36.599 some types of algae that create yellowish snow. Of course, 0:05:36.680 --> 0:05:38.960 as any third grader or dog owner can tell you, 0:05:39.240 --> 0:05:47.039 that's not the only way to get yellow snow. Today's 0:05:47.040 --> 0:05:50.000 episode was written by Mark Mancini and produced by Tyler Clang. 0:05:50.360 --> 0:05:52.960 For more on this and lots of other rose tinted topics, 0:05:53.040 --> 0:06:06.719 visit our home planet, how stuff works dot com.