CAREER: Fluxes and Structures in Double-Diffusive Convection

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The significance of double-diffuse mixing for water-mass transformation and determining the structure of the temperature-salinity relationship in all oceans is becoming increasingly clear over the last few years. One of the most intriguing aspects of double-diffuse convection is related to its ability to transform smooth vertical gradients into the stepped structures consisting of mixed layers separated by thin stratified interfaces. Recent field data from the tropical Atlantic has shown that vertical fluxes due to salt fingers within thermohaline staircases are significant (by order of magnitude) enhanced over non-staircase regions with similar stratifications. (Schmitt et al., 2005). Thus, it is vital to improve our understanding of the thermohaline staircase formation, evolution and the large scale consequences. In this CAREER award, a researcher at the Naval Postgraduate School will quantify the double-diffusive transport in both smooth gradients and thermohaline staircases, developing a clearer insight into the origin of staircases and specifying the conditions for their information. The work will involve a combination of numerical process modeling and theoretical analysis. Inferences from the theory and model runs will be used to interpret the oceanic fine-and microstructure data and results of the laboratory experiments. The results from this study will resolve the controversy with regard to the dynamics of the thermohaline staircases, the magnitude of the heat and salt mixing rates, and their variation with environmental parameters. The newly developed theory by the principle investigator will invoke the thickness of the mixed layers and the resulting diapycnal fluxes, will be explored. In addition to the intellectual merit of the work, the proposed teaching activities will target the Naval Postgraduate School students and expose them to the physics of the ocean microstructure by developing a special topics course, expanding the distance learning program, and advising several graduate students.