A bizarre underwater "icicle of death" has been filmed by a BBC crew.


With timelapse cameras, specialists recorded salt water being excluded from the sea ice and sinking.


The temperature of this sinking brine, which was well below 0C, caused the water to freeze in an icy sheath around it.


Where the so-called "brinicle" met the sea bed, a web of ice
formed that froze everything it touched, including sea urchins and
starfish.
The unusual phenomenon was filmed for the first time by
cameramen Hugh Miller and Doug Anderson for the BBC One series Frozen
Planet.





The icy phenomenon is caused by cold, sinking
brine, which is more dense than the rest of the sea water. It forms a
brinicle as it contacts warmer water below the surface.
Mr Miller set up the rig of timelapse equipment to capture
the growing brinicle under the ice at Little Razorback Island, near
Antarctica's Ross Archipelago.
"When we were exploring around that island we came across an
area where there had been three or four [brinicles] previously and there
was one actually happening," Mr Miller told BBC Nature.
The diving specialists noted the temperature and returned to the area as soon as the same conditions were repeated.


"It was a bit of a race against time because no-one really knew how fast they formed," said Mr Miller.


"The one we'd seen a week before was getting longer in front of our eyes... the whole thing only took five, six hours."