Ice stalactite
Encyclopedia
An ice stalactite forms beneath sea ice
when a flow of extremely cold, saline water is introduced to an area of ocean
water, being the undersea equivalent of a stalactite
or icicle
.
Known since the 1960s, the generally accepted model of their formation was proposed by the US oceanographer Seelye Martin in 1974. The formation of a brinicle was first filmed in 2011 by producer Kathryn Jeffs and cameramen Hugh Miller and Doug Anderson
for the BBC series Frozen Planet.
A brinicle can, under the proper conditions, reach down to the seafloor. To do so, the flow of supercold brine from the icepack overhead must continue, the surrounding water must be significantly less saline than the brine, the water cannot be very deep, the overhead ice pack must be still, and currents in the area must be minimal or still. If the surrounding water is too saline, its freezing point will be too low to create a significant amount of ice around the brine plume. If the water is too deep, the brinicle is likely to break free under its own weight before reaching the seafloor. If the icepack is mobile or currents too strong, strain will break the brinicle.
Under the right conditions, including favorable ocean floor topography, a brine pool
may be created. However, unlike brine pools created by cold seeps
, brinicle brine pools are likely to be very transient as the brine supply will eventually cease.
On reaching the seafloor, it will continue to accumulate ice as surrounding water freezes. The brine will travel along the seafloor in a down-slope direction until it reaches the lowest possible point, where it will pool. Any bottom-dwelling sea creatures, such as starfish or sea urchins
can be caught in this expanding web of ice and be trapped, ultimately freezing to death.
produces marked changes in the composition of the unfrozen water. When water freezes, most impurities are forced out of solution; even ice from seawater is relatively fresh compared with the seawater it is formed from. As a result of forcing the impurities out, sea ice
is very porous and spongelike, quite different from the solid ice produced when fresh water freezes.
As the seawater freezes and salt is forced out, the surrounding water becomes more saline. This lowers its freezing temperature and increases its density. The lower freezing temperature means that the surrounding water does not freeze to the ice immediately, and the higher density means that it sinks. Thus tiny tunnels called brine channels are created all through the ice as this supersaline, supercooled water sinks away from the frozen pure water. The stage is now set for the creation of a brinicle.
As this supercooled saline water reaches unfrozen seawater below the ice, it will cause the creation of additional ice. If the brine channels are relatively evenly distributed, the ice pack grows downward evenly. However, if brine channels are concentrated in one small area, the downward flow of the cold water, now so saline that it cannot freeze at its normal freezing point, begins to interact with unfrozen seawater as a flow. Just as hot air from a fire rises as a plume, this cold water descends as a plume. Its outer edges begin to accumulate a layer of ice as the surrounding water, cooled by this jet to below its freezing point, ices up. This is a brinicle: a "chimney" of ice that contains a flow of this supercold, supersaline water.
When the brinicle becomes thick enough, it becomes self-sustaining. As ice accumulates around the down-flowing cold jet, it forms an insulating layer that prevents the cold, saline water from diffusing and warming. As a result, the ice jacket surrounding the jet grows downward with the flow. It is like an icicle turned inside-out; rather than cold air freezing liquid water into layers, down-rushing cold water is freezing the surrounding water, enabling it to descend even deeper. As it does, it creates more ice, and the brinicle grows longer.
A brinicle is limited in size by the depth of the water, the growth of the ice fueling its flow, and the surrounding water itself. In 2011, brinicle formation was filmed for the first time.
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
when a flow of extremely cold, saline water is introduced to an area of ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
water, being the undersea equivalent of a stalactite
Stalactite
A stalactite , "to drip", and meaning "that which drips") is a type of speleothem that hangs from the ceiling of limestone caves. It is a type of dripstone...
or icicle
Icicle
An icicle is a spike of ice formed when water dripping or falling from an object freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source , and the resulting melted water runs off into an area where the ambient temperature is below the freezing...
.
Known since the 1960s, the generally accepted model of their formation was proposed by the US oceanographer Seelye Martin in 1974. The formation of a brinicle was first filmed in 2011 by producer Kathryn Jeffs and cameramen Hugh Miller and Doug Anderson
Doug Anderson (photographer)
Doug Anderson is a Scottish wildlife photographer.- Early life :Anderson was born in Glasgow. His father Stan was a civil engineer and his mother Anne, an artist. He discovered photography and the sea at a young age. During annual trips to the family home in Lamlash, on the Isle of Arran,...
for the BBC series Frozen Planet.
Structure
At the time of its creation, a brinicle resembles a hollow pipe of ice reaching down from an ice sheet. Inside the pipe is the supercold, supersaline water being produced by the growth of the ice above, accumulated through brine channels. At first, a brinicle is very fragile; its walls are thin and it is largely the constant flow of brine that sustains its growth. However, as ice accumulates and becomes thicker, the brinicle becomes more stable.A brinicle can, under the proper conditions, reach down to the seafloor. To do so, the flow of supercold brine from the icepack overhead must continue, the surrounding water must be significantly less saline than the brine, the water cannot be very deep, the overhead ice pack must be still, and currents in the area must be minimal or still. If the surrounding water is too saline, its freezing point will be too low to create a significant amount of ice around the brine plume. If the water is too deep, the brinicle is likely to break free under its own weight before reaching the seafloor. If the icepack is mobile or currents too strong, strain will break the brinicle.
Under the right conditions, including favorable ocean floor topography, a brine pool
Brine pool
Brine pools are large areas of brine on the ocean basin. These pools are bodies of water that have a salinity three to five times greater than the surrounding ocean. For deep-sea brine pools, the source of the salt is the dissolution of large salt deposits through salt tectonics...
may be created. However, unlike brine pools created by cold seeps
Cold seep
A cold seep is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool...
, brinicle brine pools are likely to be very transient as the brine supply will eventually cease.
On reaching the seafloor, it will continue to accumulate ice as surrounding water freezes. The brine will travel along the seafloor in a down-slope direction until it reaches the lowest possible point, where it will pool. Any bottom-dwelling sea creatures, such as starfish or sea urchins
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
can be caught in this expanding web of ice and be trapped, ultimately freezing to death.
Formation
The formation of ice from salt waterSalt water
Salt water or saltwater may refer to:* Saline water, water containing salts* Brine, with salt* Brackish water, water that is saltier than fresh water, but not as salty as seawater* Seawater, water from oceans or seas...
produces marked changes in the composition of the unfrozen water. When water freezes, most impurities are forced out of solution; even ice from seawater is relatively fresh compared with the seawater it is formed from. As a result of forcing the impurities out, sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
is very porous and spongelike, quite different from the solid ice produced when fresh water freezes.
As the seawater freezes and salt is forced out, the surrounding water becomes more saline. This lowers its freezing temperature and increases its density. The lower freezing temperature means that the surrounding water does not freeze to the ice immediately, and the higher density means that it sinks. Thus tiny tunnels called brine channels are created all through the ice as this supersaline, supercooled water sinks away from the frozen pure water. The stage is now set for the creation of a brinicle.
As this supercooled saline water reaches unfrozen seawater below the ice, it will cause the creation of additional ice. If the brine channels are relatively evenly distributed, the ice pack grows downward evenly. However, if brine channels are concentrated in one small area, the downward flow of the cold water, now so saline that it cannot freeze at its normal freezing point, begins to interact with unfrozen seawater as a flow. Just as hot air from a fire rises as a plume, this cold water descends as a plume. Its outer edges begin to accumulate a layer of ice as the surrounding water, cooled by this jet to below its freezing point, ices up. This is a brinicle: a "chimney" of ice that contains a flow of this supercold, supersaline water.
When the brinicle becomes thick enough, it becomes self-sustaining. As ice accumulates around the down-flowing cold jet, it forms an insulating layer that prevents the cold, saline water from diffusing and warming. As a result, the ice jacket surrounding the jet grows downward with the flow. It is like an icicle turned inside-out; rather than cold air freezing liquid water into layers, down-rushing cold water is freezing the surrounding water, enabling it to descend even deeper. As it does, it creates more ice, and the brinicle grows longer.
A brinicle is limited in size by the depth of the water, the growth of the ice fueling its flow, and the surrounding water itself. In 2011, brinicle formation was filmed for the first time.
External links
- Video Footage – Attenborough-narrated timelapse of brinicle formation
- 'Brinicle' ice finger of death
- Attenborough's polar trip: The tech that made Frozen Planet possible