In some mountains, the thick white mass of snow can sometimes be covered with red spots, giving the impression of a real crime scene at high altitude. This natural phenomenon, whether it is meteorological or biological, is in fact a very negative sign of the health status of the glaciers involved.
Mountain hiking can hold surprises on some rocky slopes. In recent years, hikers have taken pictures of pink, red, or orange snow on glaciers in particular in the Alpsmultiplied. The so-called “red snow”, “glacier blood” or even “snow melonmelon It is actually an increasingly common sight. In the past, mountaineers thought it was just sediment mineralsmineralsTo some extent The sand coming from the desert is regularly blown by the windYou reach the tops of the mountains.
“Live” red snow in motion
But then scientists discovered that this snow blood was actually alive. These are microscopic algae, Chlamydomonas nivalis The most common, or Ancylonema nordenskioeldiiwhich has freezing temperatures.
This little plant organism is packed with a carotenoid, the same red pigment that colours TomatoesTomatoesand maple leaves toAutumnAutumn. This type of algae is also known for coloring some lakes and streams red or pink when conditions are high Weather reportWeather report enough.
These algae do not appear suddenly It is present in some glaciers Throughout the year. during his rest periodwinterwinterIt is simply invisible. But once spring comes, the algae are able to move with the water from the glaciers to reach the height that suits them: between 3,000 and 3,700 meters in general, but some classifyclassify They also appear at an altitude of less than 2,000 metres. In contact with strong rays sunsunRed pigment is activated to protect algae from burning: the colorthe color It finally works as a sunscreen.
Algae feed on the minerals in the ground, and when the snow begins to fall again in large quantities and the sun goes down at the end of summer, the algae again enters a period of rest, loses its colors and is buried in the snow.
A large amount of red snow is considered a bad sign
Even if the appearance of these algae is normal, the meltingmelting highlighted snow Global WarmingGlobal Warming It seems to make it more and more visible: the more snow melts, the more seasonseason The lower the winter, the higher the algae infestation. This red snow has the effect of reducing albedo, with up to 13% less reflectance. Like the the heatthe heat It is absorbed, and not redirected into the sky, and the melting of snow and glaciers accelerates. Thus warming increases the amount of red algae present, and the more algae spread, the greater the snow melt.
the ” icy blood Very common in the Sierra Nevada mountains of California, Greenland and Antarctica, but also in the Italian Alps, as in Glacier Priscina. Just as tomato juice is able to stain clothes permanently, “ice blood” can leave indelible marks on hikers’ trousers. If everyone knows that you shouldn’t eat snow in the mountains, then you should take less risk of swallowing red snow: seaweed is a powerful laxative. On the other hand, red snow is consumed without worry by some worms, primary objectsprimary objectsAnd arthropods;arthropods;.