At a depth of approximately 11,942 feet (3,640 meters) below the surface of the Greenland Sea, methane is constantly leaking from the seafloor. Along the Molloy Ridge, gas bubbles rise through the water, oil seeps from buried sediments, and swarms of animals gather in complete darkness, feeding on chemicals instead of sunlight.
This site, known as Freya's Hydrate Mounds, lies deeper than any previously recorded cold gas hydrate seep. Footage from remotely operated vehicles shows methane and oil seeping from the seafloor, surrounded by dense communities of animals living without sunlight. Described in Natural communicationsThe find pushes known hydrate systems nearly 5,905 feet (about 1,800 meters) deeper than expected and links the seepage to life commonly found in Arctic hydrothermal vents.
“This discovery rewrites the rules of behavior in Arctic deep-sea ecosystems and the carbon cycle,” said Juliana Panieri, the expedition's chief scientist, in her report. press release. “We have discovered an ultra-deep system that is both geologically dynamic and biologically rich, with implications for biodiversity, climate processes and the future management of the High North.”
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A deep-sea system that's still changing
Various fauna have been discovered in the Hydrate Mounds of Freyja.
(UIT/Ocean Census/REV Ocean/CC BY-ND)
What sets Freyja's hydrate mounds apart is not only their depth, but also their obvious activity. Images of the seafloor show mounds in varying states—some intact, others collapsing—suggesting the system is constantly changing rather than frozen in place.
Chemical evidence helps explain what drives these changes. The methane released at the site originated deep underground, rather than being produced by microbes on the seafloor. The crude oil samples point to a source that is millions of years old, indicating that liquids moved slowly upward through the Earth's crust over long periods of time. This sustained movement appears to both create and destabilize hydrate mounds.
One of the clearest signs of this activity is how far the methane travels. Gas plumes were seen rising more than 10,826 feet (about 3,300 meters) through the water—some of the highest ever recorded—carrying carbon from the depths of the seafloor to the ocean above.
“These are not static deposits,” Panieri said. “They are living geological formations that respond to tectonics, deep heat flows and environmental changes.”
What Freya's Hydrate Mounds Could Mean for the Future of the Arctic
Biology aside, Freya's hydrate mounds offer scientists a rare opportunity to understand how methane behaves at extreme depths. The site provides ultra-deep landing to study how gas moves from buried geological sources to the ocean, particularly in the Fram Strait, where changing ocean conditions can affect the stability of hydrates. Observations from the seafloor show that hydrate structures form, destabilize, and collapse over time, highlighting the dynamic role these systems play in the Arctic carbon cycle.
The same conditions that allow methane to escape from the seafloor also sustain life. At this site, researchers documented chemosynthetic communities living alongside active seeps—an unusual combination at this depth. When the team compared these communities to those found elsewhere in the Arctic, they found a marked overlap with animals living near hydrothermal vents. According to the researchers, these similarities suggest that ultra-deep cold vents may contribute to the biodiversity of the deep Arctic.
“There are likely to be more very deep, cold gas hydrate seeps in this region, such as the Freya Mounds, waiting to be discovered, and the marine life that thrives around them may be critical to the contribution to the biodiversity of the deep Arctic,” John Copley, who led the biogeographic analysis, said in a press release.
“The connections we found between life in this place and hydrothermal vents in the Arctic indicate that these island habitats on the ocean floor will need to be protected from any future impacts of deep-sea mining in the region,” Copley concluded.
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