The deepest hydrothermal vents on Earth. 5km down under Arctic ice, heat-loving bacteria thrive in freezing water heated by volcanic chimneys.
An ultraslow volcanic world
The Gakkel Ridge is a section of the Mid-Ocean Ridge system that separates the North American and Eurasian tectonic plates. Stretching 1,800 kilometers from Greenland to Siberia under the Arctic Ocean, it is the slowest-spreading ridge known on Earth. The plates here move apart at a rate of less than one centimeter per year. Because of this ultra-slow speed, scientists initially predicted the ridge would be geologically quiet, with little to no volcanic or hydrothermal activity.
Initial evidence of venting was detected during a 2001 international expedition, which found chemical and temperature anomalies in the water column along a 1,100 km stretch of the rift valley. This suggested the presence of nine to twelve separate vent sites. In 2007, the "Arctic Gakkel Vents Expedition" (AGAVE) visually confirmed the vents, discovering large fields of pyroclastic volcanic deposits—unconsolidated ash from explosive eruptions, a surprising find at such immense pressure. One major vent area, the Aurora Vent Field, sits on a volcanic mound at a depth of approximately 3,888 meters.
Life without the sun
The ecosystems at the Gakkel Ridge vents are unlike those found at other deep-sea vent sites. The deep Arctic has been isolated from the deep Atlantic and Pacific for millions of years, leading to a unique evolutionary path for its inhabitants. The communities are dominated by microbial life, which forms thick mats on the seafloor. Vent fauna is sparse. Instead of the large tubeworms or shrimp common at other ridges, the visible life at the Aurora Vent Field consists mainly of a new species of limpet, small gastropods, and a type of amphipod.
These organisms survive through chemosynthesis, a process that uses chemical energy instead of sunlight. The vents release superheated fluids with hydrogen, hydrogen sulfide, and methane, which are the primary energy sources. Microbial carbon fixation rates in the plumes rising from the vents are up to 50 times higher than in the surrounding deep Arctic water. The unique geochemistry and the presence of life under a permanent ice cap make the Gakkel Ridge an analogue for scientists studying how life might arise on icy moons like Europa or Enceladus.
💡Fun Facts
The Gakkel Ridge spreads at a full rate of between 6 and 14 millimeters per year, among the slowest on the planet.
The existence of the ridge was predicted by Soviet explorer Yakov Yakovlevich Gakkel in the 1950s, but active volcanoes along it were only confirmed in 1999 by a nuclear submarine.
The 2007 AGAVE expedition used two new autonomous underwater vehicles, PUMA and JAGUAR, to locate and map the vent sites beneath the ice.
Navigating the permanent sea ice is a major challenge; research vessels must follow small cracks in the ice, called "leads," scouted by helicopter.