Deepest Gas Hydrate Cold Seep ever discovered in the Arctic: international research team unveils Freya Hydrate Mounds at 3,640 m Depth.  

A multinational scientific team led by UiT has uncovered the deepest known gas hydrate cold seep on the planet.  The discovery was made during the Ocean Census Arctic Deep – EXTREME24 expedition and reveals a previously unknown ecosystem thriving at 3,640 metres on the Molloy Ridge in the Greenland Sea. The groundbreaking findings regarding the Freya Hydrate Mounds, which hold scientific significance and implications for Arctic governance and sustainable development, have recently been published in Nature Communications.  

The recently documented Freya Hydrate Mounds hosts active methane seepage, crude oil emissions, and resilient chemosynthetic communities. These findings significantly expand the known depth limit for gas hydrate outcrops by nearly 1,800 meters and highlight unexpected biological connections between deep-sea seeps and hydrothermal vents in the Arctic region. 

“This discovery rewrites the playbook for Arctic deep-sea ecosystems and carbon cycling,” said Giuliana Panieri, Professor at UiT and now Director of CNR-ISP, and Chief Scientist of the expedition, together with Alex Rogers.  “We found an ultra-deep system that is both geologically dynamic and biologically rich, with implications for biodiversity, climate processes, and future stewardship of the High North.” 

"There are likely to be more very deep gas hydrate cold seeps like the Freya mounds awaiting discovery in the region, and the marine life that thrives around them may be critical in contributing to the biodiversity of the deep Arctic" said Jon Copley of the University of Southampton, UK, who led the biogeographic analysis of the new discovery. "The links that we have found between life at this seep and hydrothermal vents in the Arctic indicate that these island-like habitats on the ocean floor will need to be protected from any future impacts of deep-sea mining in the region."   

Key Finding on Freya Hydrate Mounds  

The discovery regarding the deepest hydrate deposits has revealed important insights into the Arctic's geological and ecological dynamics. These deposits, at a staggering depth of 3,640 meters, greatly surpass the typical occurrences found at depths of less than 2,000 meters. Such findings challenge our previous understanding of hydrate formation, offering an opportunity to further explore these environments. 

Additionally, the observation of methane gas flares rising more than 3,300 meters through the water column is particularly significant. These flares are among the tallest ever recorded globally, underscoring the unique geological processes occurring in this region; moreover, thermogenic gas and crude oil sourced from Miocene-aged sediments indicate a complex history of deep geological fluid migrations that reflect the intricate interactions between geological formations over time. 

The ecological aspect of these findings is equally fascinating. The presence of chemosynthetic communities, dominated by specialised organisms such as siboglinid and maldanid tubeworms, snails, and amphipods, highlights the unique adaptations of life forms in this extreme environment. Furthermore, the substantial overlap of these faunal communities with those near hydrothermal vents suggests a previously unrecognised level of ecological connectivity across deep-sea habitats in the Arctic. Moreover, the hydrate mounds observed in various stages of growth and dissociation reveal that this ecosystem is not static but rather active and evolving.  

A New Perspective on Deep Carbon Cycling 

Understanding the new findings about the role of hydrate systems within broader environmental contexts could also have implications for climate change discussions, particularly concerning methane release and its effects on global warming. 

In this regard, the Freya mounds represent an ultra-deep natural laboratory for studying methane behaviour in the water column and the potential impacts of warmer waters in the Fram Strait. The hydrate structures appear to form, destabilise, and collapse over time— a dynamic sequence documented on the seafloor using advanced ROV imaging technology. 

“These are not static deposits,” Panieri added. “They are living geological features, responding to tectonics, deep heat flow, and environmental change.” 

Implications for Arctic governance and sustainable development 

In conclusion, these findings collectively offer a detailed narrative about the dynamic interplay between geology and biology in the Arctic deep-sea environment. They call for intensified research efforts to explore and understand the complexities of these habitats, their evolutionary significance, and their response to both natural and anthropogenic changes. 

However, the most significant aspect is that the discovery occurs at a time of increased international attention on the Arctic Ocean. These ultra-deep ecosystems are located in areas that are increasingly being considered for resource exploration, underscoring the importance of evidence-based environmental assessments. 

“Understanding these unique habitats is essential for safeguarding biodiversity and supporting responsible decision-making in polar regions,” Panieri noted. 

About the Expedition 

The Ocean Census Arctic Deep – EXTREME24 expedition (https://oceancensus.org/expeditions/arctic-deep/) is led by the Arctic University of Norway and brought together leading experts in geology, biology, and geochemistry. It is part of the EXTREME Project (https://uit.no/project/extremes), which leads interdisciplinary research on extreme environments in the Arctic and beyond. High-resolution imagery and ROV samples support the scientific analyses in the upcoming publication on the Freya hydrate mounds. 

The Nippon Foundation-Nekton Ocean Census is the largest global programme to discover ocean life. During the Arctic expedition and workshop at UiT in 2024, it sampled and analysed the specialised ecosystems adapted to life in the Arctic Deep Sea. 

ROV Aurora, operated by REV Ocean, conducted the deep dives that produced the high-resolution imagery and sampling central to these findings, offering rare access to one of the deepest cold seep systems known.