Cameramen for BBC One’s seven-part nature series Frozen Planet captured an interesting phenomenon in the freezing waters at Little Razorback Island, in Antarctica. Using a rig of time-lapse equipment, the crew filmed what looks like an icy finger of death as it extended from the ice sheet and touched the sear floor, freezing everything around it.

This icicle of death is called a brinicle. Dr Mark Brandon at the Open University explains how such a brinicle is formed:

In winter, the air temperature above the sea ice can be below -20C, whereas the sea water is only about -1.9C. Heat flows from the warmer sea up to the very cold air, forming new ice from the bottom. The salt in this newly formed ice is concentrated and pushed into the brine channels. And because it is very cold and salty, it is denser than the water beneath.

The result is the brine sinks in a descending plume. But as this extremely cold brine leaves the sea ice, it freezes the relatively fresh seawater it comes in contact with. This forms a fragile tube of ice around the descending plume, which grows into what has been called a brinicle.

See a brinicle forming in this little excerpt from the Frozen Planet series.

It is the first time that the crew has managed to film a brinicle forming. You can read more about how they captured the footage on the BBC website.

[via +Paul Scott]