International scientists aboard the Schmidt Ocean Institute’s R/V Falkor (too) discovered a biodiverse deep-sea ecosystem in the Bellingshausen Sea after the A-84 iceberg broke away from the George VI Ice Shelf on January 13, 2025. The 510-square-kilometre iceberg’s departure exposed a seafloor that had been concealed under 150-metre-thick ice for centuries, revealing species including giant phantom jellies and octopuses at depths of 1,300 metres.
A-84 Iceberg Calving Reveals Hidden Antarctic Ecosystem
The departure of iceberg A-84, which the Schmidt Ocean Institute describes as roughly the size of Chicago, provided a rare window into a previously inaccessible underwater world. Using the remotely operated vehicle (ROV) SuBastian, researchers conducted an eight-day survey of the seabed. They found a vibrant community of marine life flourishing in total darkness.
Expedition scientist Dr. Patricia Esquete stated that the team didn’t expect to find such a thriving ecosystem. Based on the size of the animals observed, Esquete noted that these communities may have existed there for decades or even hundreds of years.
The ROV documented a wide array of species, including:
- Giant phantom jellies: Jellyfish growing up to one metre wide with oral arms exceeding 10 metres.
- Deep-sea predators: Octopuses (one filmed at 1,150 metres) and squid.
- Benthic life: Huge sea spiders, icefish, brittle stars, and solitary hydroids.
- Structural organisms: Large sponges and clusters of anemones.
Did you know? While its main body is relatively small, its ribbon-like oral arms can stretch over 10 metres to capture prey in the dark Antarctic waters.
The Mystery of Nutrient Survival Beneath Ice Shelves
The discovery challenges existing understandings of how life survives in total isolation from sunlight. According to the research team, deep-sea communities usually rely on organic material sinking from the ocean surface. However, this specific region was entombed beneath thick ice for centuries, blocking that primary food source.
Researchers now hypothesize that ocean currents may be transporting essential nutrients into the area, sustaining the biodiverse population despite the lack of surface contact. The team suspects they may have discovered several species entirely new to science.
Predicting Sea Level Rise via Geological Clues
Beyond biological discovery, the mission focused on the geological impact of the retreating ice sheet. Sasha Montelli, an expedition scientist, stated that ice loss from the Antarctic Ice Sheet is a major contributor to global sea level rise. Montelli noted that this work provides the longer-term context needed to improve projections of future change and inform actionable policies.
To gather this data, the team deployed autonomous underwater gliders. Preliminary findings indicate a significant influx of meltwater from the retreating ice shelf, which appears to be linked to heightened biological productivity in the region.
Challenger 150 and the Future of Deep-Sea Exploration
This expedition is part of Challenger 150, a global deep-sea research initiative endorsed by UNESCO. Dr. Jyotika Virmani, executive director of the Schmidt Ocean Institute, described the timing of the A-84 calving as a “serendipitous moment” that allowed scientists to witness an untouched part of the world.
The mission’s findings contrast with previous assumptions about the sterility of sub-shelf environments. By comparing the biological productivity of the newly exposed seabed with areas that lost ice cover years ago—such as the southeastern end of the Ronne Entrance—scientists can better track how ecosystems react to ice loss.
Frequently Asked Questions
How big was the A-84 iceberg?
It measured 510 square kilometres, which is approximately the size of Chicago.
How did the animals survive without sunlight?
Scientists hypothesize that ocean currents transport the necessary nutrients to sustain life in the absence of sinking organic matter from the surface.
What technology was used to film the seafloor?
The team used the ROV SuBastian for deep-sea imaging and autonomous underwater gliders to measure water chemistry.
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