Posted on May 3, 2022 31
The answer to the question of what color Antarctic ice is seems obvious. But is it true?
The vast expanses of Antarctica... When you talk about them, you immediately picture in your mind a colorless landscape. The snow is white, so is the ice, well, maybe blue-white.
Antarctic ice is not necessarily white. They can be blue, blue, yellowish, green and even black. The color of the ice depends on many factors. The origin of the ice, its age, chemical and mineral impurities, and traces of biological activity all contribute to this.
In addition, the color of the ice very depends on how it is illuminated. In the early morning, at noon and at sunset, the light can be quite different. And if clouds color the sunlight pink, purple, scarlet and other shades of the spectrum, the ice also takes on very interesting shades.
The Antarctic ice sheet covers 98% of Antarctica. It is the largest accumulation of ice on Earth - in fact, it contains about 61% of all freshwater on Earth. Antarctic ice is both continental and marine in origin. Continental ice often contains mineral impurities. It is stronger than sea ice because it is completely fresh. Whereas sea ice is formed with sea water, which means it can contain traces of marine organisms.
If you see transparent ice in Antarctica, it has most likely recently formed from seawater. It is barely visible on the surface of the sea. It may look like dried out “snowy mush” or just a thick layer of frozen fresh water.
Yes, the same color one expects to see in Antarctica. But why is the ice white? The fact is that during the freezing of the ice, there may be a lot of tiny air bubbles in it. These air bubbles scatter sunlight. And that’s why ice appears completely white to us.
This color is typical of glaciers that are hundreds or even thousands of years old. You can’t get this color quickly. Glaciers are constantly growing in size, covered with new and new layers of snow. And under the growing weight of the glacier, air bubbles shrink and then partially dissolve. As a result, the ice becomes clearer. However, the oxygen it contains absorbs all colors except blue.
Green and yellow
If ice is formed from seawater, it often captures the impurities it contains as well. Green and yellow shades can be produced if the water has had many flecks of phytoplankton, which is what tiny algae is called. Also, with seawater can freeze cells and other microorganisms, and sometimes rock dust, rich in minerals.
Black icebergs that have formed from the base of a glacier can be black. But sometimes it can turn over, and then that “littered” side is above the surface of the water. An iceberg can be so muddy that it is easy to confuse it with a rock.
And then there are “black” icebergs of another type. They are formed from very firm and dense ice, the oldest ice compared to the others. This ice is completely transparent and in a dark sea looks black and hardly noticeable. That’s why sailors call such icebergs black - not only because of the color but also because they are the most dangerous to ships.
This type of ice forms on glaciers that often melt and then freeze again. And as a result, the ice becomes layered, like a Napoleon pie. Layers of such ice have different densities and contain different amounts of air bubbles, which also vary in size. If such an iceberg breaks apart, its fragments can be turned any way they want. So, the layers of such ice will not be arranged only horizontally.
Antarctica is a very unusual and fascinating place, which does not look like a colorless white desert, as we imagine it.