Diapycnal advection by double diffusion and turbulence in the ocean
Citable URI
https://hdl.handle.net/1912/4697Location
Brazil BasinDOI
10.1575/1912/4697Keyword
Turbulence; Ocean currentsAbstract
Observations of diapycnal mixing rates are examined and related to diapycnal
advection for both double-diffusive and turbulent regimes.
The role of double-diffusive mixing at the site of the North Atlantic Tracer Release
Experiment is considered. The strength of salt-finger mixing is analyzed in terms
of the stability parameters for shear and double-diffusive convection, and a nondimensional ratio of the thermal and energy dissipation rates. While the model for
turbulence describes most dissipation occurring in high shear, dissipation in low
shear is better described by the salt-finger model, and a method for estimating
the salt-finger enhancement of the diapycnal haline diffusivity over the thermal
diffusivity is proposed. Best agreement between tracer-inferred mixing rates and
microstructure based estimates is achieved when the salt-finger enhancement of
haline flux is taken into account.
The role of turbulence occurring above rough bathymetry in the abyssal Brazil
Basin is also considered. The mixing levels along sloping bathymetry exceed the
levels observed on ridge crests and canyon floors. Additionally, mixing levels
modulate in phase with the spring-neap tidal cycle. A model of the dissipation
rate is derived and used to specify the turbulent mixing rate and constrain the
diapycnal advection in an inverse model for the steady circulation. The inverse
model solution reveals the presence of a secondary circulation with zonal character.
These results suggest that mixing in abyssal canyons plays an important role in
the mass budget of Antarctic Bottom Water.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1999
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Suggested Citation
Thesis: St. Laurent, Louis C., "Diapycnal advection by double diffusion and turbulence in the ocean", 1999-09, DOI:10.1575/1912/4697, https://hdl.handle.net/1912/4697Related items
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