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Diapycnal advection by double diffusion and turbulence in the ocean

Author(s)
St. Laurent, Louis C
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Other Contributors
Woods Hole Oceanographic Institution.
Advisor
Ramond W. Schmitt.
Terms of use
M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582
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Abstract
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
Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1999.
 
Includes bibliographical references (leaves 129-139).
 
Date issued
1999
URI
http://hdl.handle.net/1721.1/69185
Department
Joint Program in Physical Oceanography.; Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences.; Woods Hole Oceanographic Institution.
Publisher
Massachusetts Institute of Technology
Keywords
Joint Program in Physical Oceanography., Earth, Atmospheric, and Planetary Sciences., Woods Hole Oceanographic Institution.

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  • Earth, Atmospheric and Planetary Sciences - Ph.D. / Sc.D.
  • Earth, Atmospheric, and Planetary Sciences - Ph.D. / Sc.D.

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