It's like something out of a Harry Potter or a Lord of the Rings movie, a death finger of ice that wiggles downward and freezes everything in its path, killing starfish and sea urchins, the deadly finger then weaves its way to the ocean floor.
Now for the first time, using time-lapse cameras, a BBC crew has captured the moment brine from the sea ice sinks, forming a deadly 'brinicle' threatening life on the sea floor with a frosty incantatory fate. The temperature within the sinking brine finger is well below freezing and anything that gets in its path is literally frozen to death. The creeping ice finger was captured by cameramen Hugh Miller and Doug Anderson for the BBC One series Frozen Planet.
An icy sheaf surrounds the finger and anything that is in, or near, its path will meet an icy demise. Cold, sinking brine is more dense than the sea water that surrounds it. The brinicle is formed as it contacts warmer water below the surface. When sea water freezes it forms tiny networks of ice channels within the sea body.
During winter months, temperatures can drop to around -20c but the sea will still be around -2c (30f). The heat flows upwards from the warmer part of the sea to where the cold air is, this then forms new ice from the bottom of the sea bed. The brine then sinks like the "icicle of death", freezing relatively fresh seawater it comes in contact with (and unfortunate sea creatures), writes Dr Mark Brandon, polar oceanographer with The Open University .
The brinicle captured in the video above was recorded at Little Razorback Island, near Antarctica's Ross Archipelago.
Brinicles are found in both the Arctic and the Antarctic, but calm waters are required for them to grow as long as the ones the Frozen Planet team observed.