Meet The Giant Arctic Jellyfish That Defy Freezing Temperatures

Written by Matthew Russell

Beneath the icy stillness of the Arctic, where sunlight barely filters through thick sea ice, jellyfish are rewriting the rules of survival. For years, scientists assumed these delicate creatures could not withstand the region’s brutal winters. But that assumption shattered when researchers discovered adult Chrysaora melanaster jellyfish drifting under the frozen Chukchi Sea, tentacles trailing through near-freezing water.

The findings stunned marine biologists. Footage captured by Columbia University researchers using underwater vehicles revealed dozens of fully grown jellyfish gliding along the shallow seafloor. Their bells stretched nearly 24 inches across, and their tentacles extended up to 10 feet long. These jellyfish weren’t dormant, dying, or clinging to survival. They were alive and active, defying decades of assumptions about Arctic marine life, Live Science reports.

Arctic jellyfish are surviving the winter in their adult stage.

Life Under Ice Moves Slowly but Surely

To capture this rare glimpse, researchers rode snowmobiles across miles of frozen ocean and drilled through four feet of ice. Cameras dropped into the water below revealed not only jellyfish but a surprising abundance of other life — from algae to crustaceans. What stunned scientists most was that these jellyfish appeared healthy and fully developed, in the medusa stage, not the dormant polyp form previously believed to be their only means of winter survival, according to Columbia Climate School.

The cold helps them. It slows their metabolism, allowing them to conserve energy. And the ice above shields them from turbulent winter storms.

As Columbia biologist Andy Juhl put it, “Life under sea ice is like living in a refrigerator — everything slows down.” This slow-paced existence may help these jellyfish survive for years, not just months as once assumed.

Scientists found jellyfish living under four feet of Arctic ice.

From Arctic Shelters to Antarctic Giants

Jellyfish don’t just surprise us in the north. Thousands of miles south, in the icy waters of Antarctica, researchers aboard the Schmidt Ocean Institute’s expedition recently filmed one of the rarest marine animals ever seen — the ghost jellyfish. This deep-sea giant (*Stygiomedusa gigantea*) spans over three feet wide, with flowing oral arms stretching more than 30 feet. It drifts silently through the dark, catching prey without the aid of tentacles. It was filmed at 1,300 meters depth in a region only accessible because a massive iceberg had recently broken free, the Stewartville Star reports.

Ghost jellies are rarely seen — only 120 sightings have ever been recorded since their discovery in 1899. Their immense size and unusual feeding methods set them apart, but it’s their reproduction that draws perhaps the most curiosity. Unlike most jellyfish, ghost jellies give birth to live young. The juveniles emerge directly from the parent’s mouth after developing inside its bell, a trait called viviparity, according to Live Science.

These jellyfish were once believed to die off each winter.

Adaptation in Every Form

While ghost jellies are deep-sea dwellers, some were filmed at surprisingly shallow depths — just 260 feet in Antarctic waters. Researchers suggest that in polar regions, shifts in sunlight and prey behavior may draw these jellies closer to the surface.

Both Arctic and Antarctic jellyfish species show how adaptable these animals can be. In the Arctic, jellyfish once assumed to vanish in winter now appear to thrive, aided by the very cold that was thought to be their limit. In Antarctica, a creature thought to be relegated to unreachable depths rises when opportunity allows, providing rare glimpses of life in Earth’s most extreme waters.

What unites them isn’t just their beauty or rarity. It’s their resilience — silent drifters shaped by pressure, cold, and darkness, yet still pulsing through the oceans, undeterred.

Ghost jellyfish in Antarctica can grow over 30 feet long.

Climate Change Could Tip the Balance

Despite their resilience, these jellyfish may face new threats. According to Columbia Climate School, arctic species like *C. melanaster* rely on thick sea ice for shelter. As climate change causes rapid ice loss, these jellyfish — and many creatures that depend on sea ice — may see their habitats disappear. At the same time, jellyfish in warmer parts of the world are thriving, even swarming, in response to warming waters and fewer predators.

In the far north, though, it may be the opposite. With less ice, cold-adapted jellies could decline. In the case of these jellyfish, warming may simply mean vanishing.

Still, these discoveries are a reminder of how much we have yet to understand. The creatures beneath the ice and beyond the reach of sunlight continue to defy expectations, reminding us that the ocean — even in its coldest corners — is alive with mystery.