Australia: The Land Where Time Began

A biography of the Australian continent 

Brinicles - Ice Fingers of Death

According to the author¹ ice formed from the freezing of sea water has a tiny network of brine channels within it. The air temperature above the sea ice can drop to less than -20^oC in winter, while the water below the ice is about -1.9^oC, which results in sea ice being formed from the bottom up as heat is transferred from the water to the air above it. As the ice forms the salt is excluded and the very concentrated brine is moved to the brine channels from which it moves down the channels.

As it is very cold and concentrated it sinks in a descending plume to the sea floor. As a result of the brine leaving the sea ice being extremely cold the relatively fresh water around the plume freezes on contact with the plume, forming a fragile ice tube around the descending plume, the result being a "brinicle".

Brinicles are present in the Arctic and the Antarctic, but the conditions have to be relatively calm for them to form as long as the one filmed by the Frozen Planet team.

 Sources & Further reading

1. Dr Mark Brandon, Polar Oceanographer, Open University, UK