Brinicles are hollow icicles that grow downward beneath polar sea ice. As seawater freezes, it expels a stream of extremely cold, concentrated brine. This dense liquid sinks, freezing the surrounding seawater into a tube as it descends. If a brinicle reaches the seabed, the flow can spread across the bottom as an advancing sheet of ice, trapping slow-moving marine animals in its path.
Brinicles
