The importance of water in its various forms (solid, liquid and gas) within the atmosphere cannot be underestimated, as it plays a vital role in the interdependence between the water cycle and life on Earth. When it rains or snows, our immediate assumption is that the water is colorless and that the snow, intact and pristine, has a white hue. Consequently, we tend to believe that ice, being a different manifestation of the liquid element, will also lack color or appear white, without contemplating alternative possibilities. However, Does the ice color exist? What color is it really?
In this article we are going to tell you everything you need to know about the ice color and their characteristics.
Ice formation
At a pressure of one atmosphere, pure water has the ability to freeze at 0°C. However, unlike most substances, when water freezes, it actually expands in volume, resulting in a decrease in density. This unique characteristic plays a crucial role in preventing the complete freezing of Earth's polar oceans. Ice formed from frozen water instead of sinking, which causes its accumulation over time and its spread to other bodies of water. This phenomenon has important implications for life as we currently understand it, making it unsustainable under such conditions.
It is well known that the Sun emits white light, which is actually a combination of several colors. This can be observed by passing a beam of light through a glass prism or by witnessing a rainbow, both of which result from the phenomena of refraction, reflection and dispersion. When sunlight passes through raindrops, it undergoes bending and separation, creating a distinct sequence of colors. This sequence begins with red on the outermost side and progresses through the orange, yellow, green, blue, indigo and finally violet towards the center, forming a continuous gradient of colors.
Differences between snow color and ice color
Sometimes, the snowy peaks acquire a reddish or intense brown tint, the result of the interaction of the snow with clay condensation nuclei or sandstones of a similar shade. However, it is typical for this weather phenomenon to display a white appearance, due to its exceptional ability to reflect sunlight (approximately 70% to 90% of incoming solar radiation). This high reflectivity is the result of the numerous reflections that occur within air bubbles trapped in the snow, concentrated in a thin layer near the surface of the snowpack.
If the water were to freeze completely without impurities, transparent ice would be obtained, something rare in nature. However, during the freezing process, air bubbles become trapped within the ice, acting as prisms that create numerous reflections and disperse the colors of the visible spectrum, ultimately giving the ice its white appearance. The intensity of whiteness is directly proportional to the amount of reflection that occurs, which correlates with the amount of air bubbles presentThis white hue plays a crucial role in regulating the Earth's temperature by effectively reflecting sunlight, contributing significantly to the albedo of the planet.
The reflective capacity of this coloration is important in regulating the Earth's temperature by contributing significantly to albedo, which measures the amount of solar radiation reflected back into space. Albedo is a key factor in influencing global climate and its evolution. The reduction of albedo during certain seasons at the poles is one of the factors that contribute to the phenomenon of human-induced global warming.
Places where the ice is not white
So far, the elements have been pretty predictable: colorless water, clear ice, and predominantly white snow. However, what happens when we encounter substantial icing?
In situations such as those found in ice packs, areas of perpetual ice or glaciers, the accumulation of fallen snow leads to more compacted ice, resulting in the compression of the air trapped inside and allows greater absorption of sunlight by the frozen mass.
When there are no bubbles, light has the ability to travel deeper into the ice, gradually being absorbed as it moves deeper. Sunlight is made up of various colors with different wavelengths, with red having the longest wavelength and blue the shortest. Different colors have different levels of penetration: red is easily absorbed by ice and blue can reach greater depths. Consequently, as a ray of white light goes deeper into the ice, it gradually loses colors and finally leaves only the blue hue in the frozen mass.
green ice
We have already seen that the color of ice, in general, depends on how light interacts with it. Pure ice, without impurities or air bubbles, is actually blue. This is because water absorbs longer wavelength colors (reds and yellows) more and shorter wavelength colors (blues and greens) less. However, green ice has unique characteristics that give it its distinctive color.
There are several reasons why ice may appear green:
- Presence of algae and other organisms: In some polar regions, especially Antarctica, the ice may contain small algae that have green pigments. These algae become trapped in the ice during its formation, giving the ice a greenish hue.
- Mineral impurities: Another explanation is the presence of mineral impurities in the ice. When seawater freezes, it can trap particles of iron oxides and other minerals that can have a greenish hue. These impurities are distributed within the ice, and when light passes through it, these particles can reflect and scatter light in a way that makes the ice appear green.
- Structure and density of ice: The way ice is formed and structured can also influence its color. Ice that is compressed and densified, removing air bubbles, can allow for different light transmission which, combined with other impurities, can result in a green color.
