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Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of the glacier. During compression, air bubbles are squeezed out, so ice crystals enlarge. This enlargement is responsible for the ice's blue colour.
Small amounts of regular ice appear to be white because of air bubbles inside and also because small quantities of water appear to be colourless. In glaciers, the pressure causes the air bubbles to be squeezed out, increasing the density of the created ice. Water is blue in large quantities, as it absorbs other colours more efficiently than blue. A large piece of compressed ice, or a glacier, similarly appears blue.
The blue color is sometimes wrongly attributed to Rayleigh scattering, which is responsible for the color of the sky. Rather, water ice is blue for the same reason that large quantities of liquid water are blue: it is a result of an overtone of an oxygen–hydrogen (O−H) bond stretch in water, which absorbs light at the red end of the visible spectrum. So, water owes its intrinsic blueness (as seen after > 3 meters of penetration) to selective absorption in the red part of its visible spectrum. The absorbed photons drive vibrational (normally infrared) transitions.
Once blue ice is exposed to warmer air, cracks and fissures appear in surface layers, and break up the large blue crystals of dense, pure ice. Within hours these air filled fissures cloud the surface making the ice appear white. The blue colour will not be seen again until the ice breaks or turns over to expose ice which air could not reach. For example, lucky tourists at
Blue ice is exposed in areas of the
Glaciology of Blue Ice Areas in Antarctica
* {{glaciers Bodies of ice Glaciology
Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of the glacier. During compression, air bubbles are squeezed out, so ice crystals enlarge. This enlargement is responsible for the ice's blue colour.
Small amounts of regular ice appear to be white because of air bubbles inside and also because small quantities of water appear to be colourless. In glaciers, the pressure causes the air bubbles to be squeezed out, increasing the density of the created ice. Water is blue in large quantities, as it absorbs other colours more efficiently than blue. A large piece of compressed ice, or a glacier, similarly appears blue.
The blue color is sometimes wrongly attributed to Rayleigh scattering, which is responsible for the color of the sky. Rather, water ice is blue for the same reason that large quantities of liquid water are blue: it is a result of an overtone of an oxygen–hydrogen (O−H) bond stretch in water, which absorbs light at the red end of the visible spectrum. So, water owes its intrinsic blueness (as seen after > 3 meters of penetration) to selective absorption in the red part of its visible spectrum. The absorbed photons drive vibrational (normally infrared) transitions.
Once blue ice is exposed to warmer air, cracks and fissures appear in surface layers, and break up the large blue crystals of dense, pure ice. Within hours these air filled fissures cloud the surface making the ice appear white. The blue colour will not be seen again until the ice breaks or turns over to expose ice which air could not reach. For example, lucky tourists at Tasman Glacier
Haupapa / Tasman Glacier is the largest glacier in New Zealand, and one of several large glaciers which flow south and east towards the Mackenzie Basin from the Southern Alps in New Zealand's South Island.
Geography
At in length, Tasman Glacie ...
, New Zealand in January 2011 saw an iceberg roll over to reveal startling blue ice, kept from air by staying underwater for months since the iceberg calved.
Antarctic runways
Blue ice is exposed in areas of the Antarctic
The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...
where there is no net addition or subtraction of snow. That is, any snow that falls in that area is counteracted by sublimation
Sublimation or sublimate may refer to:
* ''Sublimation'' (album), by Canvas Solaris, 2004
* Sublimation (phase transition), directly from the solid to the gas phase
* Sublimation (psychology), a mature type of defense mechanism
* Sublimate of mer ...
or other losses. Such areas are known as blue-ice area
A blue-ice area is an ice-covered area of Antarctica where wind-driven snow transport and sublimation result in net mass loss from the ice surface in the absence of melting, forming a blue surface that contrasts with the more common white Anta ...
s. These areas have been used as runways (e.g. Wilkins Runway, Novolazarevskaya, Patriot Hills Base Camp
Patriot Hills Base Camp was a private seasonally occupied camp in Antarctica. It was located in the Heritage Range of the Ellsworth Mountains, next to the Patriot Hills that gave it its name.
The camp was run by the private company Adventure Ne ...
) due to their hard surface, which is suitable for aircraft fitted with wheels rather than skis.
References
External links
Glaciology of Blue Ice Areas in Antarctica
* {{glaciers Bodies of ice Glaciology