A blue iceberg is visible after the ice from above the water melts, causing the smooth portion of ice from below the water to overturn. The rare blue ice is formed from the

compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression *Gas compression *Compression ratio, of a c ...

of pure snow, which then develops into

glacial ice A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

Icebergs An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The ...

may also appear blue due to light refraction and age. Older icebergs reveal vivid hues of green and blue, resulting from a high concentration of color,

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s, and compacted ice. One of the better known blue icebergs rests in the waters off Sermilik fjord near

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

. It is described as an electric blue iceberg and is known to locals as "blue diamond".

Physics of light and color

Blue iceberg in the Ilulissat icefjord - edited

White icebergs

Commonly seen white icebergs generally derive their color from the snow and frost remaining on the surface which results in the uniform reflection of incident

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

. Young glaciers that have not undergone years of compression, may also appear white. Due to the age of the iceberg, there remains a tremendous amount of air and reflective surfaces. The iceberg easily reflects the sun as white light.

Preferential light absorption and age

Blue icebergs develop from older, deep

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

s which have undergone tremendous pressure experienced for hundreds of years. The process releases and eliminates air that was originally caught in the ice by falling snow. Therefore, icebergs that have been formed from older glaciers have little internal air or reflective surfaces. When long

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

light (i.e. red) from the sun hits the iceberg, it is absorbed rather than reflected. The light transmitted or refracted through the ice returns as blue or blue-green. Older glaciers also reflect incident light preferentially at the short wavelength end of the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

(i.e. blue) due to

Rayleigh scattering Rayleigh scattering ( ), named after the 19th-century British physicist Lord Rayleigh (John William Strutt), is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the ...

, much in the same way that makes the sky blue.

Color spectrum and water

Light is absorbed and reflected in water. Visible white light is made up of a spectrum of colors from the rainbow, ranging from red to violet. As the light travels through the water, the waves of light from the red end of the spectrum dissipate (i.e. are absorbed), while those from the blue end, become more prominent.

Underwater divers This is a list of underwater divers whose exploits have made them notable. Underwater divers are people who take part in underwater diving activities – Underwater diving is practiced as part of an occupation, or for recreation, where t ...

have direct experience of these effects. Above the water, all the colors remain visible. As the diver swims deeper

under water The underwater environment is the region below the surface of, and immersed in, liquid water in a natural or artificial feature (called a body of water), such as an ocean, sea, lake, pond, reservoir, river, canal, or aquifer. Some characterist ...

, the colors begin to disappear, starting with red. At an approximate depth of , red is no longer visible to the naked eye. At , yellow looks greenish-blue, because the water has absorbed the yellow light. Finally, all that remains visible to the naked eye, appears as a mutation of blue or green, while the water above the surface filters out the sunlight. As the diver swims deeper into the ocean, he finds that the blue colors start to disappear, to the point where the underwater world deep below the surface, becomes completely black, devoid of any color at all.Graver, Dennis. ''Scuba diving'', 4th ed. Human Kinetics, pp. 31-32, 2010.

RMS ''Titanic''

Since 1912, reports made by witnesses of the RMS ''Titanic'' tragedy have stated that the ship hit a blue iceberg. Following the sinking and subsequent

discovery Discovery may refer to: * Discovery (observation), observing or finding something unknown * Discovery (fiction), a character's learning something unknown * Discovery (law), a process in courts of law relating to evidence Discovery, The Discovery ...

of the ''Titanic'', scientific research and forensic analysis have reconstructed the tragedy to ascertain the reliability of the statements made by the survivors. Reports released in the last decade of the 20th century have shown that a blue iceberg in the north Atlantic would have been easily detected.McCarty, Jennifer Hooper; Foecke, Tim. ''What Really Sank the Titanic: New Forensic Discoveries'', Kensington Publishing Corporation, page 67, 2009. Alternative theories suggest that

pack ice Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.).Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Unlike fast ice, which is "fasten ...

, rather than a blue iceberg, was responsible for sinking the ship.Collins, L.M. ''The Sinking of the Titanic: The Mystery Solved'', Souvenir Press, pp. 16-25, 2003.

Physics of light and color

White icebergs

Preferential light absorption and age

Color spectrum and water

RMS ''Titanic''

References

Further reading