China's Fendouzhe Reaches 5,277 Meters Beneath Arctic Ice in First Exploration of Eastern Gakkel Ridge

A descent into an Arctic frontier

China's Fendouzhe submersible reached 5,277 meters beneath Arctic pack ice during a 98-day expedition that completed 43 dives and brought scientists face to face with the eastern Gakkel Ridge for the first time. Operating from the research vessel Tan Suo San Hao, the team explored a remote underwater volcanic mountain chain stretching between Greenland and Siberia, collecting samples and recording seafloor features previously known through the blurred outlines of earlier maps.

The voyage lasted roughly three months, with 56 days spent operating in the Arctic Ocean and nearly 2,000 nautical miles traveled through waters covered by ice. Its central achievement was reaching the eastern ridge in a submersible carrying people, then bringing them safely back through a surface where shifting ice could block their exit.

Xiaoxia Huang, a marine geophysicist at the Institute of Deep-sea Science and Engineering and the expedition's chief scientist, described the eastern section as the last piece of the puzzle in Arctic geological research. She also spoke about the opportunity to observe this environment herself.

"It's really a privilege to have such an opportunity to study the deep sea in person," said Huang.

The Gakkel Ridge belongs to the global mid-ocean ridge system, where tectonic plates pull apart and new ocean crust forms. Its exceptionally slow spreading creates unusual geological conditions and makes it a valuable place to investigate how volcanic activity, seawater and living organisms interact in an environment of darkness, cold and intense pressure.

Earlier expeditions had surveyed parts of the ridge using sonar and vehicles without crews. No submersible carrying people had reached its eastern sector. The latest voyage opened that region to direct human observation, while the samples brought home await the laboratory work needed to explain what the team encountered.

How the team returned through moving ice

Sea ice covered more than 80 percent of the surface in waters where the expedition operated. For a submersible returning from several kilometers below, that coverage creates a basic safety problem: the occupants need an opening through which their vehicle can surface and receive support.

Tan Suo San Hao used its icebreaking capability to create a temporary opening before each dive. The opening served as a pool where Fendouzhe could enter the ocean and later return. Keeping that access usable required careful timing because winds and currents continually move the surrounding pack ice.

The expedition developed a method described as "ship-submersible coordination" to manage these conditions. The vessel and submersible had to work together throughout a dive, including the final approach to the surface, when an opening could have shifted or closed.

Fendouzhe sometimes paused below the surface after completing its work on the seabed. Its crew used sonar and cameras to look for open water or thinner ice that would permit a safe ascent. When necessary, the submersible waited while the support vessel cleared a route through the ice.

Christopher German, a marine geochemist at the Woods Hole Oceanographic Institution who was not involved in the mission, described why access to this part of the ocean matters scientifically.

"It's so hard to get there that anything anybody does is almost guaranteed to be exciting and different and new," German said.

The repeated dives demonstrated an ability to manage this difficult return journey across an extended expedition. According to the Chinese Ministry of Natural Resources, the mission validated the capabilities of both Fendouzhe and Tan Suo San Hao in polar ice zones, established operating procedures for extreme polar conditions and pioneered a mobile model for diving beneath ice.

Two submersibles and a new research vessel

Fendouzhe, whose name translates to "Striver," was built in China for exploration at extreme ocean depths. It can reach depths of at least 7,000 meters and had already descended to 10,909 meters at Challenger Deep in the Mariana Trench, the deepest known point in Earth's oceans.

The Arctic expedition required adaptations for temperatures close to freezing and the continuing threat of moving sea ice. Its maximum depth of 5,277 meters was shallower than the vehicle's previous Mariana Trench descent, while the ice above introduced a different operational challenge: arranging a safe place to surface.

China describes Tan Suo San Hao as the world's first comprehensive scientific research ship designed specifically for global exploration of the deep sea with icebreaking capabilities. Combining those functions allows operations throughout the year in polar regions previously accessible only during short summer periods when ice coverage was minimal.

Elmar Albers, a marine geoscientist at Germany's Alfred Wegener Institute, described the scientific promise of the expedition's technical achievement.

"The Chinese mission is poised to yield significant new insights into Earth's most extreme underwater habitats," Albers said.

The voyage also included China's first joint underwater operation involving two submersibles carrying people. Fendouzhe worked alongside Jiaolong, with the vehicles coordinating their positions, exchanging markers and filming underwater. Using two vehicles allows more extensive surveys and provides an additional layer of safety support.

Jiaolong also completed China's first dive carrying people beneath Arctic ice during the mission. Together, the two vehicles demonstrated a broader ability to operate in polar waters, while the support vessel supplied the icebreaking access needed for that work.

Why this slowly spreading ridge matters

The Gakkel Ridge is an extreme example of a mid-ocean ridge that spreads exceptionally slowly. Most such ridges spread at rates of several centimeters a year. At Gakkel, new crust forms at a pace slower than human fingernails grow.

The North American Plate and the Eurasian Plate pull apart along the ridge. Magma rises into the opening and forms new oceanic crust. Studying that process helps scientists understand volcanic activity and how ocean basins develop over geological time.

The slow rate of separation can produce distinctive geological formations and affect the hydrothermal systems that develop along the ridge. Hydrothermal systems are places where seawater enters the ocean crust, heats up underground and returns to the ocean carrying dissolved minerals.

The expedition targeted seamounts, cliff faces, underwater hills and canyons. Cameras and sonar turned indistinct shapes on earlier maps into detailed footage of the actual seafloor. Those images will help researchers examine the structure of the ridge and explain how its features formed.

Gakkel also matters to the movement of elements between Earth's interior and its surface. Water passing through crust near a ridge exchanges heat and minerals with the surrounding rock. The resulting chemical transfers connect geological activity below the seabed with conditions in the ocean above.

Researchers will use the new geological observations to compare this exceptionally slow ridge with ridges that spread faster. The findings could refine models of plate tectonics, improve understanding of how Earth's crust develops and provide a foundation for further exploration of the region.

The search for underwater hot springs

A 2003 study published in Nature revealed hydrothermal vents on the western Gakkel Ridge. The eastern sector remained unexplored by people before this expedition, making the search for vents there one of the mission's main scientific objectives.

Hydrothermal vents act like underwater hot springs. Seawater circulates through newly formed volcanic rock, becomes heated by magma beneath the seabed and flows back into the ocean with dissolved minerals. Those minerals help support unusual communities of organisms in places sunlight never reaches.

Life around such vents can obtain energy from chemical reactions involving substances such as hydrogen sulfide. This gives organisms a way to survive without relying on sunlight, which supplies the energy underlying many ecosystems nearer the ocean surface.

Huang and her team did not disclose whether they found active vent systems in the eastern Gakkel Ridge. Answering that question will require months of careful laboratory work on the material collected during the voyage.

Researchers will look for minerals, unusual water chemistry and biological communities that could indicate hydrothermal activity. Finding active vents in the eastern sector would help complete the scientific picture of the ridge and explain how life spreads and evolves in deep ocean environments.

The western discoveries established the ridge as a place where geological activity and distinctive life can occur together. The eastern expedition extends the investigation into a remote section where direct observation had previously been out of reach.

What the samples may reveal about life

The team collected sediment cores, rocks, seawater and biological specimens during nearly one hundred days at sea. Each type of material provides a different view of the ridge, from the composition of its rocks to the chemistry of its water and the organisms living around it.

Scientists observed fish and other species surviving in conditions Huang described as "the dark, the cold, the pressure and the rocks." The biological specimens could reveal new species or unusual adaptations to an environment that is cold, dark and under extreme pressure.

Laboratory studies will examine how the collected organisms relate to known species and how they survive in these conditions. Understanding their adaptations could contribute to fields ranging from medicine to biotechnology, although the work begins with identifying and studying the specimens themselves.

The search for life around hydrothermal vents also connects the expedition with astrobiology, the study of the possibility of life beyond Earth. Scientists suspect that chemical energy could support life in oceans beneath the icy shells of Europa, which orbits Jupiter, and Enceladus, which orbits Saturn.

Arctic vent ecosystems offer a way to study how organisms can live without sunlight in an ocean beneath ice. Samples from the Gakkel Ridge could help researchers refine models of what ecosystems in those distant oceans might look like.

The connection rests on a shared question about energy: how living things obtain what they need when sunlight is absent. On Earth, hydrothermal communities show how chemical reactions can provide that energy. Studying them gives scientists a concrete example to use when examining possible habitats elsewhere in the solar system.

Connecting the deep ocean with Arctic warming

The Arctic is warming at a rate two to three times faster than the global average. Changes in the region affect ecosystems, sea levels and weather patterns far beyond the polar ocean, connecting this remote expedition with conditions experienced by communities elsewhere.

The Gakkel Ridge moves heat and chemicals through the deep ocean as seawater circulates through ocean crust. Exchanges of heat and minerals affect water chemistry and circulation, which form part of the wider climate system.

Detailed measurements from the ridge can help scientists refine climate models used in planning for coastal communities, infrastructure and disaster preparedness. The deep Arctic belongs to the same connected system that shapes unusually mild winters and bitter cold spells in temperate regions.

The expedition collected observations of water temperature, salinity, chemical composition and biological communities throughout the water column. Salinity describes how salty the water is; the water column means the ocean from its surface down to the seabed.

Measurements gathered now provide a baseline, or starting reference, for comparison with future observations. Researchers can use that reference to examine changes in the deep Arctic environment and the effects of continued warming.

The Arctic also serves as a sentinel for changes elsewhere in the climate system. Shifts in its ocean temperatures, chemistry and ecosystems can signal wider developments that later affect other regions. The expedition's observations will support research into those connections and into rapid Arctic climate change.

China expands its presence in polar research

China sent five research ships, including an icebreaker, into the Arctic during the summer preceding the expedition's account. That presence accompanied the country's wider growth in polar activity over the past decade, involving icebreakers, research vessels and submersibles operating without crews.

Beijing describes China as a "near-Arctic state" and presents its work in the region as part of a "peaceful scientific development" strategy. Its stated areas of interest include climate research, marine biodiversity and mapping resources beneath the sea.

The successful completion of 43 dives carrying people in waters covered by ice makes China the only country currently capable of conducting continuous dives of this kind in the heavily ice covered Arctic Ocean. The expedition demonstrated both the vehicles' ability to work at depth and the vessel's ability to maintain access through ice.

The Arctic's increasing accessibility as climate change reduces ice coverage is opening shipping routes and exposing potential resources. China's growing technical proficiency positions it to participate in future development opportunities and emerging trade routes through the region.

The operational procedures developed during this voyage could also expand the possibilities for future scientific exploration. China's growing capabilities may affect international discussions about Arctic governance, research cooperation and environmental protection.

The mission therefore has two connected dimensions: a scientific effort to understand a little explored ridge and a demonstration of China's ability to sustain complicated operations in polar waters. Its geological and biological findings will depend on the analysis of the samples and observations brought home.

From the expedition to the laboratory

The 98-day voyage has ended, but extracting its scientific results will take much longer. Researchers expect years of detailed work to understand the full significance of the samples and video footage.

Rocks will be examined for their mineral composition and age. Sediment cores will be studied for chemical and biological markers, while biological specimens will be compared with known species. Seawater samples will help researchers investigate the chemical conditions along the ridge.

The work spans several stages of exploration:

• In 2003, a study published in Nature revealed hydrothermal vents on the western Gakkel Ridge.
• During the summer preceding this account, China dispatched five research ships, including an icebreaker, into the Arctic.
• During the 98-day expedition, Fendouzhe completed 43 dives, reaching a maximum depth of 5,277 meters, while the team spent 56 days operating in the Arctic Ocean.
• As of January 18, 2026, the expedition had concluded, with laboratory analysis needed to answer questions about vents, geology and biological specimens.

Scientists will pay particular attention to evidence of active hydrothermal systems in the eastern ridge. They will also examine how its crust differs from that of faster spreading ridges and what its organisms reveal about survival in extreme environments.

The detailed mapping provides a starting point for further research, while the samples allow questions raised during the dives to be investigated on land. Each result may generate new questions about the geology, chemistry and life of the deep Arctic.

The eastern Gakkel Ridge has now entered the scientific map through direct human exploration. The expedition's immediate achievement was reaching it repeatedly beneath moving ice; its lasting contribution will come from explaining the seafloor, water and organisms the team observed.

Key Points

• Fendouzhe completed 43 dives during a 98-day expedition and reached a maximum depth of 5,277 meters.
• The mission carried out the first exploration by people of the eastern Gakkel Ridge, between Greenland and Siberia.
• The team spent 56 days operating in the Arctic Ocean and traveled nearly 2,000 nautical miles through waters covered by ice.
• Coordination between Tan Suo San Hao and the submersible enabled dives where sea ice covered more than 80 percent of the surface.
• Fendouzhe and Jiaolong conducted China's first joint underwater operation involving two submersibles carrying people.
• Scientists collected rocks, sediment cores, seawater and biological specimens for geological, climate and ecosystem research.
• The team had not disclosed whether it found active hydrothermal vents in the eastern ridge.
• Laboratory analysis is expected to take years to reveal the expedition's full scientific results.