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Vertical and temporal vorticity observations at Juan de Fuca Ridge: Hydrothermal signatures
Author(s) -
Joyce Terrence M.,
Can Glenn A.,
Pashinski Dave,
Helfrich Karl R.,
Harrington Stephanie A.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl01309
Subject(s) - geology , ridge , plume , anticyclone , vorticity , magnitude (astronomy) , shear (geology) , mid ocean ridge , geophysics , panache , potential vorticity , seismology , atmospheric sciences , vortex , petrology , meteorology , paleontology , physics , astronomy
Moored current measurements made from April 1994 to June 1995 reveal the vertical and temporal structure of the vorticity over the northern segment of the Juan de Fuca Ridge. At a depth of 2100m, near the thermal and particle maximum associated with the neutrally buoyant hydrothermal plume, the relative vorticity is anticyclonic with a mean value of nearly −0.09 f , with variability of the same magnitude. This arises from cross‐ridge shear in the horizontal currents at this level. In the vertical, the anticyclonic shear has a peak value at plume level decreasing in magnitude both upward and downward from depths of 2100–2150m. As the bottom is approached, the transverse shear changes sign with cyclonic values of up to 0.09 f below 2250m depth. This vorticity signature is suggestive of dynamics of a line source of buoyant fluid entering the plume at its neutral density horizon and not due to individual point sources.