Hydrothermal activity along the global mid-ocean ridge system
and at active seamounts introduces a He-rich signal into the deep ocean
basins, which can be used to trace patterns of ocean circulation
and mixing. This hydrothermal helium signal is especially strong
in the Pacific Ocean, where the spreading rate of the ridges is
the greatest. In several areas of the Pacific the hydrothermal
activity is of sufficient strength to produce intense helium
plumes which clearly define the regional circulation. Among these
are (1) a pair of helium plumes at 2500-m depth, which extend
westward from the East Pacific Rise at 10°N and 15°S
into the interior of the Pacific basin; (2) a helium plume at
2000-m depth extending southwest from sources on the Juan de Fuca
Ridge in the northeast Pacific; and (3) a plume at 1100-m depth
emanating from Loihi Seamount at 20°N, which extends
eastward from Hawaii to the coast of Mexico. The flow field
implied by the helium distribution appears to be in reasonable
agreement with Reid’s [1997] steric height analysis for
the Pacific.
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