It’s known as brinicle although they also call it ice finger of death. Brinicle is a current or flow of cold brine that is introduced in an ocean with much warmer temperature. They’ve collected photos and recorded videos of it since 1960, but it wasn’t until 2011 that it became popular, when Hugh Miller and Doug Anderson made Frozen Planet, a documentary for BBC One.
What is it exactly?
Let’s think of it as a tube of ice that moves in an ocean of different temperatures. As it’s too low, the “ice tube” progresses without melting and without losing its stability. Indeed, as we saw in the post about cooling beers, when you add salt to water that will freeze, the freezing point will lower a lot more. Now consider brinicle’s situation, where ice meets sea’s salty water. Although water’s temperature is much lower than ice’s, this one increases its mass, it becomes stronger and gains size, becoming a striking icy arm of death that progresses steadily.
But enough talk! Here’s the video to take look at the issue and make it all clear:
Okay, so how is it formed?
The water that carries salt, typical of seas, with low temperatures can reach freezing. However, there are differences in composition regarding normal ice. A sea ice has different properties, it’s spongier and has a higher content of porosity.
During the freezing process, the salt’s forced to come out of the solution. Therefore, the water’s in contact with this first icing will salinize. The cycle starts over again: such water will lower its freezing point (by having salt) and increase its density. From here it’s being created the brine channel.
If the channel comes into contact with the sea, as we have said, it’ll increase in size and be fed by itself. The brinicle flows down, where the temperature is lower. That’s why in the video it looks as an icicle that reaches the floor of the seabed and keeps going.
If you think about it like that, if it feeds itself, it wouldn’t have an end and would go on forever. However, in the brinicle’s recordings in 2011 it’s shown how it’s influenced by depth, temperature and the surrounding water itself.