How a Brinicle Works

By: Patrick J. Kiger  | 
brinicle, underwater icicle
The video above features the first time a brinicle formation has been captured on video. BBC

You're probably not ever going to go diving in the waters of the Arctic and Antarctic. But if you ever do, there's a chance that you may come upon one of the more bizarre sights in nature: a brinicle.

Basically, a brinicle — sometimes also called an ice stalactite — is a descending tube that projects downward from floating sea ice on the surface of the ocean. Imagine an icicle hanging on your house's roof gutter, except that a brinicle's length may be measured in feet instead of inches, and instead of rainwater, it's formed from a super-salty saline water solution called brine.


It Starts As Sea Ice Cracks

As an brinicles-and-the-origin-of-life/">article in Technology Review explains, brinicles form because when seawater along the ocean surface freezes to form ice, it exudes a high concentration of salt. That increases the salinity of nearby sea water, which in turn lowers its freezing point, so that it stays liquid even though it's really, really cold. (In a way, this is the opposite of the reverse osmosis process that desalination plants use to turn seawater into drinking water.) Pockets of that brine can get trapped inside the ice pack.

If the sea ice cracks, though, something bizarre can happen to those pockets. The freed brine will leak out and, because it's denser than water, it will sink downward toward the sea floor. On the way down, the super-cold brine will freeze any surrounding water that it comes in contact with. As the water frezes, it forms an icy tube around the brine. Brinicles are incredibly delicate, vulnerable to only the slightest touch. As such, they require relatively calm conditions at sea for them to grow, so they're not all that common.


Oceanographers Paul Dayton and Seelye Martin first observed and described brinicles in the early 1970s, and Martin actually managed to grow simulated brinicles in his Seattle laboratory, according to a 2012 National Geographic article (excerpted here). In 2011, A BBC film crew, which was diving in the waters around Little Razorback Island near Antarctica's Ross Archipelago, actually recorded the formation of a brinicle, which took about five to six hours.


The Danger of Underwater Icicles

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A brinicle forms when heavier-than-water brine freezes the seawater around it.

A brinicle is a surreal, creepy sight — so creepy, in fact, that a British tabloid once described it as "the underwater icicle of death" and warned that it "kills everything in its path." And while that may be a bit hyperbolic, brinicles can indeed be lethal to bottom dwelling sea creatures that wander into the pools of concentrated brine that form beneath them on the ocean floor, according to Andrew Thurber, an assistant professor in ocean ecology and biogeochemistry at Oregon State University.

"I have seen the aftermath in person (the pools of dead animals) and then videos of them actually getting caught," says Thurber via email. "They are a very, very localized problem for animals. They tend to only occur in the shallows, and the species that occur there tend to be both abundant and common. So while small patches of dead animals that result from them, overall they very likely play a minor if any role in the population size of those animals."


Fortunately, they're only a threat to smaller marine life such as sea urchins, and not to bigger animals like seals, whales or humans who happen to go diving at the frigid poles, according to Thurber.

Wrapping Up

The Brine icicle is not only a marvel of the natural world but also a testament to the complex and often unseen interactions within our oceans. These 'icy fingers of death,' as dramatic as they may sound, play a relatively minor role in the broader ecological landscape of the polar regions.

Their formation process, driven by a combination the freezing temperature of the ocean and it's natural brine supply, is a stark reminder of the delicate balance that governs our natural world. While they pose little threat to larger marine animals, their impact on smaller sea creatures highlights the interconnectedness of life and the environment.


Brinicles serve as a fascinating example of nature's ability to create both beauty and peril, a reminder that even in the most remote corners of our planet, there are wonders and mysteries waiting to be explored. As we continue to uncover the secrets of our oceans, brinicles stand as a symbol of the awe-inspiring and sometimes harsh realities of the natural world.