Hydrothermal processes on the Gakkel Ridge. This research programme (PI: T. Shank, WHOI, USA) for the exploration and investigation of the Gakkel Ridge hydrothermal vents and associated fauna.

Distinct faunal assemblages are associated with different mid-ocean ridge systems within and between ocean basins. The present isolation of the Arctic Ocean and its separation from all other ridge systems raises fundamental questions about the evolution and ecology of Arctic vent fauna.  Hydrographic barriers and physical geologic features enclosing the Arctic Ocean spreading centers may pose a significant directional barrier to either historical or more recent dispersal of vent species. With no apparent deep-water connection between  the Arctic and other ocean basins, Arctic hydrothermal species have likely evolved in isolation from other vent-endemic fauna. Taxonomic and molecular characterization of Arctic fauna are thus critical for understanding the faunal diversity within the Arctic Ocean and assessing the historical migratory pathways utilized by these vent species.

The Gakkel Ridge is the slowest-spreading mid-ocean ridge on Earth. During the AMORE cruise in 2001, nine vent sites were located to within ~2-5 km, corresponding to at least one vent site every 100 km. The aim of this planned project is to further explore these sites through phased survey strategies using the AUVs Jaguar and Puma, and well as a towed real-time imaging and discrete sampling system, to determine how these potentially unique ecosystems relate to those in known biogeographic regions.

Through autonomous systematic and adaptive photographic imaging surveys (and benthic sampling), the  distribution, abundance, and variation in microhabitat structure as they relate to hydrothermal activity and geological features will be assessed.  Through detailed genetic investigation of recovered fauna, we will assess the role isolation has played in the evolution and biogeography of Arctic vent fauna.

Gakkel Ridge (T. Shank, WHOI)

The scientific questions driving the proposed programme are:

1) What controls the distribution of hydrothermal vents on the slowest spreading ridge on earth?

2) What do the physical and chemical characteristics of vent plumes in the Arctic reveal about ridge geological and biological processes?

3) What are the geochemical characteristics of Arctic vent fluids and how are they related to known fluid chemistries from around the world? - to an arctic axial heat source?

4) What kinds of biological communities and novel ecological strategies exist on the Gakkel ridge and how have they evolved in “global” isolation? How are they related to fauna in the Atlantic and Pacific?

Field tests with a newly-constructed towed real-time imaging and benthic sampling system, and two new AUVs, Puma and Jaguar specifically designed for locating and sampling vent systems and fauna in the Arctic Ocean . (T. Shank, R. Sohn, H. Singh, WHOI)

July - August 2007: Expedition to the Gakkel Ridge on board the Swedish Ice Breaker Oden funded by NSF Office of Polar Programs, NASA Astrobiology ASTEP Program and the Woods Hole Oceanographic Institution.

Post Cruise Report:

The Arctic GAkkel Vents Expedition (AGAVE) took place on the IB Oden from July 1 ­ August 10, 2007. The expedition represented an international collaboration between scientists in the United States, Sweden, Japan, and Germany, and was part of an International Polar Year (IPY) project entitled, ‘Biogeography and Geological Diversity of Hydrothermal Venting on the Ultra-Slow Spreading Arctic Mid-Ocean Ridge’ led by Rob Reeves-Sohn, Hanu Singh, Tim Shank, Susan Humphris, and Hedy Edmonds.

Four primary assets were employed for this research ­ a CTD/rosette, the PUMA AUV, the JAGUAR AUV, and a high-definition video-guided sampling wireline system, CAMPER.  PUMA (“Plume Mapper") ­ was used to search for vents utilizing temperature and chemical sensors, as well as a novel laser-guided optical backscatter sensor.  The approach was to utilize PUMA to "localize" the seafloor position of potential venting sources via searching wide areas with mapping tools that include sensors to detect temperature, chemicals and particle signals of hydrothermal plumes.  Once a venting area was "localized", the AUV JAGUAR was to be used to conduct a high-resolution bathymetry survey of a smaller area as well as collect magnetic data and images of the biological communities and vent areas.  The wireline CAMPER high-definition imaging, sampling, and sensing capabilities were then to be used to obtain high-resolution seafloor imagery and identify and collect benthic samples using either a clamshell “grab” sampler or a suction “slurp” sampler. The major accomplishments of the AGAVE 2007 cruise include the: 1) discovery of the Asgard volcanic chain at 85°E segment; 2) discovery of extensive and apparent chemosynthethic microbial mats covering the volcanoes, apparently fed by weak fluid discharge from cracks in young volcanic surfaces; 3) discovery of basaltic glass fragments covering large portions of the seafloor providing evidence of  explosive volcanism; 4) detailed mapping of water column plumes in peridotite (7°E) and basalt (85°E) hosted segments; 5) development and demonstration of the CAMPER wireline system for high-resolution imaging and sampling of the deep seafloor under ice; 6) development of the PUMA and JAGUAR AUVs and demonstration of deep AUV operations from within the ice pack; and 7) demonstration of acoustic communications and long/short baseline navigation in the deep Arctic Ocean.

WHOI scientists, technicians and partners are continuing to advance the development of AUVs for different environments.  Deeper versions of the Seabed, called Jaguar and Puma, have been used to look for hydrothermal vent sites under the ice in the Arctic Ocean