Determination of advection and diffusion in a thermohaline staircase region

Thermohaline staircases consisting of a series of well mixed layers approximately 30 m thick are found at depths of 300-500 m in a region of the tropical North Atlantic spanning 48° to 58°W, 8° to 17° N. Density ratios ( ... ) with values near 1 indicate a double diffusive origin for the structure (Schmitt, 1981,1986). Determining the importance of double-diffusive mixing to the regional advection - diffusion balance is the subject of this study. Using hydrographic and current meter data collected in the C-SALT program of 1985 (Schmitt, 1987), we construct inverse models in both cartesian and density coordinates and seek bounds on the cross isopycnal mixing in the staircase region. In cartesian coordinates, the role of diffusion was not well resolved, probably due to inadequacy of the steady state model in the presence of eddies. By reformulating the problem in boxes bounded by isopycnals which more closely follow the layers, and solving directly for cross isopycnal fluxes of salt and heat, the resolution of the diffusivities was improved. Inversions were done on data from the spring and fall CTD surveys. The average salt diffusivity in the step region was estimated from the isopycnal inversions to be ks = (2.8 + 1.3)cm2 /s in spring and ks = (3.9 ± 2.2)cm2 /s in fall.

Department dc:contributor.department

Joint Program in Oceanography

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

1988

Author dc:creator

• Federiuk, Joyce Marie

Advisor dc:contributor.advisor

• Carl Wunsch.

• Joint Program in Oceanography.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• 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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/53530

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/53530