Brinicle

As seawater freezes in the polar ocean, salt brine concentrates are expelled from the sea ice, creating a downward flow of dense, extremely cold, saline water, with a lower freezing point than the surrounding water.

When this plume comes into contact with the neighboring ocean water, its extremely low temperature causes ice to instantly form around the flow.

As the seawater freezes and salt is forced out of the pure ice crystal lattice, the surrounding water becomes more saline as concentrated brine leaks out.

A brinicle has now been formed, resembling an inverted "chimney" of ice enclosing a downward flow of this supercooled, super salinated water.

The inner wall temperature of the stalactite remains on the salinity-determined freezing curve, so as the stalactite grows and the temperature deficit of the brine goes into the growth of ice, the inner wall melts to dilute and cool the adjacent brine back to its freezing point.

Inside the pipe is extremely cold and saline water produced by the growth of the sea ice above, accumulated through brine channels.

To do so, the supercold brine from the pack ice overhead must continue to flow, the surrounding water must be significantly less saline than the brine, the water cannot be very deep, the overhead sea 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.

Under the right conditions, including favorable ocean floor topography, a brine pool may be created.

[3] 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.

Brinicle formation;
  1. When water freezes, most impurities are expelled from the ice crystals, resulting in the formation of cavities containing salt-water brine, and thus making sea ice very porous.
  2. The surrounding water becomes more saline as concentrated brine leaks out.
  3. The brine-rich water remains liquid, and its increased density causes this water to sink, setting the stage for the creation of a "brinicle".
  4. Its outer edges begin accumulating a layer of ice as the surrounding water, cooled by this jet to below its freezing point, ices up in a tubular or finger shape and becomes self-sustaining.
  5. The down-flowing cold jet continues to grow longer downward, and reach the seafloor.
  6. It will continue to accumulate ice as surrounding water freezes. The brine will travel along the seafloor in a down-slope direction.