The existence and approximate location of the Gakkel Ridge were predicted bySoviet polar explorerYakov Yakovlevich Gakkel and confirmed on Soviet expeditions in the Arctic around 1950. The Ridge is named after him, and the name was recognized in April 1987 bySCUFN (under that body's old name, the Sub-Committee on Geographical Names and Nomenclature of Ocean Bottom Features).[1]
Until 1999, it was believed to be non-volcanic; that year, scientists operating from a nuclear submarine discovered activevolcanoes along it. The largest, theGakkel Ridge Caldera, is asupervolcano that erupted approximately 1.1 million years ago during thePleistocene.[3] In 2001 two research icebreakers, the GermanPolarstern and the AmericanHealy, with several groups of scientists, cruised to the Gakkel Ridge to explore it and collect petrological samples. Among other discoveries, this expedition found evidence ofhydrothermal vents. In 2007,Woods Hole Oceanographic Institution conducted the "Arctic Gakkel Vents Expedition" (AGAVE), which made some unanticipated discoveries, including the unconsolidated fragmentedpyroclastic volcanic deposits that cover the axial valley of the ridge (whose area is greater than 10 km2). These suggest volatile substances in concentrations ten times those in the magmas of normal mid-ocean ridges.[4] Using "free-swimming"robotic submersibles on the Gakkel ridge, the AGAVE expedition also discovered what they called "bizarre 'mats' of microbial communities containing a half dozen or more new species".[5] A hydrothermal site, named "Aurora", was discovered in 2014.[6][7] Aurora has elevated levels ofmethane and high temperatures, suggesting interactions between water andultramafic rock below the vent field (rather thanbasalt reactions). Aurora's geochemistry may resemble that of theRainbow Vent Field in the Atlantic Ocean.
The Gakkel Ridge is approximately 1,800 kilometres (1,100 mi) long and is the slowest known spreading ridge on earth, with a rate of less than one centimeter per year. It continues to the south and connects with the Knipovich Ridge.[8]
The Gakkel ridge is not offset by anytransform faults. The ridge does have segments with variable orientation and varying degrees of volcanism: the Western Volcanic Zone From the Lena trough (7° W, to 3° E longitude), the Sparsely Magmatic Zone (from 3° E to 29° E longitude), and the Eastern Magmatic Zone (from 29° E to 89°E).[9] The gaps of volcanic activity imply very cold crust and mantle, probably related to the very low spreading rate, but it is not yet known why some parts of the ridge are more magmatic than others.[10] Some earthquakes have been detected from the mantle, below the crust, which is very unusual for a mid-ocean ridge.[11] It confirms that the mantle and crust of Gakkel ridge, like some segments of theSouthwest Indian Ridge, are very cold.
The Gakkel ridge features several confirmed and inferred hydrothermal fields, including Aurora (visually confirmed in 2014) and Lucky B (dredged in 2001).[12][13][14] More sites have been inferred, but not confirmed due to difficulties with ice at higher latitudes.
^Michael, P. J.; Langmuir, C. H.; Dick, H. J. B.; Snow, J. E.; Goldstein, S. L.; Graham, D. W.; Lehnert, K.; Kurras, G.; Jokat, W.; Mühe, R.; Edmonds, H. N. (June 2003). "Magmatic and amagmatic seafloor generation at the ultraslow-spreading Gakkel ridge, Arctic Ocean".Nature.423 (6943):956–961.Bibcode:2003Natur.423..956M.doi:10.1038/nature01704.PMID12827193.S2CID4312652.
Edmonds, H. N.; Michael, P. J.; Baker, E. T.; Connelly, D. P.; Snow, J. E.; Langmuir, C. H.; Dick, H. J. B.; Mühe, R.; German, C. R.; Graham, D. W. (January 2003). "Discovery of abundant hydrothermal venting on the ultraslow-spreading Gakkel ridge in the Arctic Ocean".Nature.421 (6920):252–256.Bibcode:2003Natur.421..252E.doi:10.1038/nature01351.PMID12529639.S2CID4392497.
