What Are Brinicles and How Do They Form?

Brinicles are underwater icicles of freezing brine that form beneath sea ice and freeze everything they touch on the seafloor. Scientists call them the “finger of death” because these deadly frozen columns can reach temperatures of -20°C (-4°F) while sinking through seawater that’s only -1.9°C (28.6°F).

How Brinicles Form

When sea ice forms on the ocean surface, it expels salt downward into the water below. This creates hypersaline brine that is both extremely dense and extremely cold. The dense brine sinks rapidly through the surrounding seawater, and because it’s so much colder than the ambient water temperature, it freezes the seawater around it as it descends.

This process creates a hollow tube of ice that continues growing downward like an underwater stalactite. The brine inside this frozen tube remains liquid due to its high salt content, even at temperatures that would freeze normal seawater. This allows the brinicle to continue extending toward the seafloor.

The Deadly Impact on Marine Life

When a brinicle reaches the ocean floor, it doesn’t simply stop growing. Instead, the freezing brine spreads outward across the seafloor, creating a pool of ice that engulfs everything in its path. Slow-moving creatures like sea urchins, starfish, and other bottom-dwelling organisms become trapped and frozen alive.

The process happens slowly enough that you can watch it in real time, but fast enough that these creatures cannot escape. The expanding ice essentially creates a frozen wasteland on what was previously a thriving patch of seafloor.

First Footage Captured in 2011

For decades, scientists knew brinicles existed, but no one had ever captured their formation on film. That changed in 2011 when BBC cameras filming for the documentary series “Frozen Planet” successfully recorded a brinicle forming beneath Antarctic sea ice.

The footage stunned scientists because it showed the complete process from formation to seafloor impact. The time-lapse photography revealed just how devastating these underwater icicles can be to marine ecosystems.

Brinicles Beyond Earth

The discovery has implications beyond our planet. Astrobiologists believe that similar phenomena could be occurring on Jupiter’s moon Europa, which harbors a vast ocean beneath its icy surface. If brinicles form in Europa’s hidden seas, they could provide insights into how life might survive or struggle in extraterrestrial oceans.

The extreme conditions that create brinicles on Earth might be even more common on Europa, where the ice layer is much thicker and the underlying ocean may have different salinity levels. Understanding brinicles could help scientists prepare for what they might find when future missions explore Europa’s subsurface ocean.