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Red Ice! This is not an illusion	By Stefan Anitei, Science Editor 15th of January 2007, 13:52 GMT Adjust text size:


Ice may be colorless, but glaciers are not transparent. In fact, most glaciers reflect light, that's why they appear as white. Sometimes ice and snow appear blue, due to the absorption of red and yellow light (reflecting only the blue spectrum) (photo center). The ice absorption spectrum is similar to that of the liquid water, but the hydrogen bonding in solid state causes a shift to lower energy, which translates into a greener color. In areas with volcanic activity, volcanic ash from eruptions may turn ice in a glacier to different shades of gray (in Iceland, for example) (photo bellow). But if you walk on the ice shelf on the Antarctic or the Arctic, you will surely be very amazed by the reddish color of the ice, very similar to raspberry syrup. (photo above) Is this because of blood left by a dinning polar bear? No, no, the color stretches over large areas and � there are no polar bear in the Antarctic area. In fact, this visual phenomenon occurs only in spring. During this period, the surface of the ice starts melting. On the melted water dissolved nutrients can accumulate brought by water flows across the top of the glaciers. If we put red ice under the microscope, we will visualize millions of � tiny spherical algae! They bloom on the melted water, taking advantage of longer days and stronger sunshine. The dominant species are red algae, but among them there are also green and blue-green algae. This is a very short-lived phenomenon, and when melting advances, the algae will flow down to the sea with the water they live in. Sometimes, these algae put a distinctly red, green or blue-green color in the top of the icebergs. Till now scientists identified about 300 species associated with the "red glaciers" phenomenon, living in such harsh and cold conditions. They make photosynthesis and some use atmospheric nitrogen. The red color is given by red protective carotenoid chemicals that the alga produces against high concentrations of visible and ultra violet light reflected by the snow and ice surfaces, which can be destructive. Such algae are also found in high mountain glaciers. When you walk across red ice, the footprints you leave are even redder as the algae are concentrated when the snow is crushed, and sometimes a slight smell of fresh watermelon accompanies the phenomena. During the frozen winters of the polar zones, the algae remain in a cyst phase, covered by a resistant membrane. The algae can pass over a century in a cyst phase just to revive when the conditions are right.

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