Tm. Joyce et al., VERTICAL AND TEMPORAL VORTICITY OBSERVATIONS AT JUAN-DE-FUCA RIDGE - HYDROTHERMAL SIGNATURES, Geophysical research letters, 25(10), 1998, pp. 1741-1744
Moored current measurements made from April 1994 to June 1995 reveal t
he vertical and temporal structure of the vorticity over the northern
segment of the Juan de Fuca Ridge. At a depth of 2100m, near the therm
al and particle maximum associated with the neutrally buoyant hydrothe
rmal plume, the relative vorticity is anticyclonic with a mean value o
f nearly -0.09f, with variability of the same magnitude. This arises f
rom cross-ridge shear in the horizontal currents at this level. In the
vertical, the anticyclonic shear has a peak value at plume level decr
easing 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 0.09f below 2250m depth. This vorticity signa
ture is suggestive of dynamics of a line source of buoyant fluid enter
ing the plume at its neutral density horizon and not due to individual
point sources.