Brinicle

When seawater freezes, much of its salt is excluded from the ice crystals and becomes concentrated in pockets and channels of brine within the sea ice. Under suitable conditions, some cold, dense brine drains from the underside of the ice. As the plume descends into seawater near its freezing point, the brine can cool the adjacent water below its local freezing temperature. Ice then forms around the descending plume, producing a hollow, tube-like structure. The continuing supply of brine and the balance of heat and salt transport influence whether the tube grows and how it develops.

Brinicles grow downwards from the underside of sea ice and may extend from centimetres to several metres. They have been reported in both Arctic and Antarctic waters. The tube encloses a flow of brine, rather than being a solid icicle. Although the informal term “ice stalactite” has sometimes been used, researchers distinguish brinicles from ordinary icicles because their growth involves a cold brine plume freezing surrounding seawater.

Laboratory studies have recreated brinicle-like tubes by introducing cold brine into water with a higher freezing point. Experiments allow researchers to vary conditions such as brine composition and flow, then observe the resulting growth and structure. A 2024 study in The Cryosphere used several experimental configurations to investigate tubular ice formation from descending brine flows. A 2025 study in The Journal of Physical Chemistry C found that the salt composition of experimental brines affected brinicle growth, stability and morphology. These results help describe controlled experiments; they do not by themselves establish how often particular forms occur in the ocean.

Brinicles provide a pathway by which salt and cold water can move from sea ice into the ocean, and researchers have considered possible consequences for local mixing and ice desalination. Their distinctive geometry has also prompted work on whether related structures could form beneath the ice-covered oceans of worlds such as Europa or Enceladus. Such extraterrestrial applications remain hypotheses and laboratory analogies, not observations of brinicles on those moons.