Arctic's Deepest 'Fire Ice' Mounds Reveal a Unique and Vulnerable Ecosystem

Scientists have discovered a unique deep-sea ecosystem thriving on methane and oil seeps at the Freya Hydrate Mounds in the Arctic's Greenland Sea, representing the deepest known gas hydrate cold seep in the region. This ultra-deep habitat reveals surprising ecological connections and raises urgent questions about safeguarding polar regions from resource exploration.

Mateo Rojas

May 30, 2026 · Updated October 4, 2026 · 4 min read

In the frigid, dark waters of the Greenland Sea, scientists have discovered a previously unknown ecosystem thriving at a depth of 3,640 meters. Named the Freya Hydrate Mounds, these geological formations are fueled by seeping methane and crude oil, creating an oasis of life in an extreme environment. The discovery, made on the Molloy Ridge during the Ocean Census Arctic Deep expedition, represents the deepest known gas hydrate cold seeps in the Arctic. These mounds and the resilient communities they support offer a new window into deep-sea biodiversity and raise urgent questions about the future of resource exploration in polar regions.

The findings, detailed in a recent Nature Communications paper, reveal not only a unique habitat but also surprising ecological connections to other deep-sea features. As nations consider the prospect of mining the deep seabed, the existence of such a fragile and interconnected ecosystem highlights the critical need for evidence-based environmental stewardship in one of the planet's last frontiers.

The 'Fire Ice' Phenomenon

The Freya Mounds are built from methane hydrate, a substance often called "fire ice." This solid, ice-like material forms when water molecules trap methane gas under the immense pressure and low temperatures of the deep ocean. While methane seeps and hydrate mounds have been found elsewhere in the Arctic, they typically occur in much shallower waters, from 70 to 800 meters deep. The Freya Mounds, by contrast, were found at an unprecedented depth for this type of feature in the Arctic, comparable to that of nearby high-Arctic hydrothermal vents.

Located on the Molloy Ridge, an ultraslow-spreading mid-ocean ridge, these mounds are not static relics. Observations from the expedition confirmed they are part of an active and evolving system. The mounds are characterized by active methane seepage and crude oil emissions, which serve as the chemical foundation for the life that clusters around them. This discovery challenges previous assumptions about where such ecosystems can exist, extending the known range of these chemosynthetic habitats by approximately 1,770 meters deeper into the Arctic abyss.

The Freya Mounds Ecosystem Model

The Freya Mounds function as a self-contained but interconnected ecosystem, where geology, chemistry, and biology interact to support life in the absence of sunlight. This model explains the key components of this deep-sea oasis and the external factors that influence it.

Geological Foundation: The Mounds

The physical structures are the hydrate mounds themselves, formed by the accumulation of frozen methane. These mounds create a unique seafloor topography, providing a stable substrate for life to colonize. Their various stages of growth and dissociation indicate a dynamic environment, constantly shaped by deep-earth geological processes that release hydrocarbons from below the seabed.

Chemical Fuel: Methane and Oil Seeps

The engine of this ecosystem is the constant release of chemical energy. Active seepage of methane and crude oil from the seafloor provides the fuel for life. Instead of relying on photosynthesis, the organisms here depend on chemosynthesis—a process where microbes convert these chemical compounds into energy. This forms the base of a unique food web in the perpetual darkness of the deep sea.

Biological Community: Chemosynthetic Life

The mounds host resilient chemosynthetic communities, a collection of marine life adapted to this extreme, high-pressure environment. The fauna found at these Arctic cold seeps includes specialized organisms like siboglinid tubeworms and thyasirid clams. These creatures have symbiotic relationships with the microbes that process the methane and other chemicals, allowing them to thrive where other life cannot.

Ecological Connection: A Bridge to Other Habitats

A significant finding is the ecological link between the life at the Freya Mounds and the communities found at deep-sea hydrothermal vents. Researchers noted a substantial overlap in the types of animals present in both habitats, suggesting a previously unrecognized level of connectivity across the Arctic deep sea. This implies that these seemingly isolated oases may function as part of a larger network, crucial for the region's overall biodiversity.

Why the Freya Mounds Matter

The discovery of this ultra-deep ecosystem has significant implications that extend beyond marine biology. It touches on our understanding of Arctic biodiversity, the complexities of climate change, and the intensifying debate over the exploitation of deep-sea resources. The mounds are located in an area increasingly considered for resource exploration, making their study essential for responsible environmental assessments.

According to Jon Copley of the University of Southampton, the unique marine life thriving around these seeps may play a vital role in the biodiversity of the deep Arctic. He emphasized that the observed links between seep and vent ecosystems mean "these isolated habitats must be protected from the impacts of deep-sea mining." The research highlights how vulnerable these extreme habitats could be to human activities.

While the release of methane from the seafloor is a component of global carbon cycling, the researchers note the complexity of its climate impact. In deep waters like the Molloy Ridge, gas bubbles are often coated in a hydrate skin that inhibits their dissolution, and the methane supports local ecosystems rather than directly reaching the atmosphere. Understanding these deep hydrate systems provides a more nuanced perspective on deep carbon cycling and its role in the broader climate context.