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I. Garcia Berdeal, S. L. Hautala, M. J. Pruis, and H. P. Johnson, Diffuse hydrothermal venting into the
turbulent bottom boundary layer on
Endeavour Segment, Juan de Fuca Ridge. I.
Variability and implications for particle flux
near the seafloor, to be submitted to Deep-Sea Research I, 2006
Observations are presented that provide information on the variability of currents
and the turbulent fluxes of heat and momentum through the near-bottom boundary
layer near diffuse low-temperature hydrothermal vents on the Juan de Fuca
Ridge in the northeast Pacific. Within the bottom one meter of the water column,
the direction and magnitude of record-mean current and tidal ellipses shows a very
high degree of spatial heterogeneity. Temporal variability occurs at a variety of expected
periodicities, including tidal, inertial and 4-day variations. Vertical shear
of the prevailing current and buoyancy both make significant contributions to the
generation of turbulence. At most sites, modulation of the prevailing current by the
semidiurnal tide creates a shifting balance between mechanical and buoyant production
terms. Extreme bottom roughness of the young basalt seafloor, along with
contributions from buoyancy, lead to very high values of friction velocity. The variability
in currents and turbulent fields in the near-bottom boundary layer revealed
by these measurements presents a highly dynamic environment for the larvae of
hydrothermal organisms that reside there. |
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