Accession Number : ADA330123

Title :   Dynamics of Nonlinear Cross-Equatorial Flow in the Deep Ocean.

Descriptive Note : Doctoral thesis,

Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA

Personal Author(s) : Edwards, Christopher A.

PDF Url : ADA330123

Report Date : DEC 1996

Pagination or Media Count : 184

Abstract : The transformation of potential vorticity within and stability of nonlinear deep western boundary Currents in an idealized tropical ocean are studied using a shallow-water model. Observational evidence indicates that the potential vorticity of fluid parcels in deep western boundary currents must change sign as they cross the equator, but this evidence is otherwise unable to clarify the process. A series of numerical experiments investigate this transformation in a rectangular basin straddling the equator. A mass source located in the northwestern corner feeds fluid into the domain where it is constrained to cross the equator to reach a distributed mass sink. Dissipation is included as momentum diffusion. The Reynolds number, defined as the ratio of the mass source per unit depth to the viscosity, determines the nature of the flow, and a critical value, Re,, divides its possible behavior into two regimes. For Re < Re,, the flow is laminar and well described by linear theory. For Re just above the critical value, the flow is time-dependent, with cyclonic eddies forming in the western boundary Current near the equator. For still larger Reynolds number, eddies of both signs emerge and form a complicated, interacting network that extends into the basin several deformation radii from the western boundary, as well as north and south of the equator. The eddy field is established as the mechanism for potential vorticity transformation in nonlinear cross-equatorial flow. The analysis of vorticity fluxes follows from the flux-conservative form of the absolute vorticity equation. It is shown that the zonally integrated meridional flux of vorticity across the equator using no slip boundary conditions is virtually zero even in the strongly nonlinear limit suggesting that the eddies are extremely efficient vorticity transfer agents.

Descriptors :   *EQUATORIAL REGIONS, *OCEAN CURRENTS, *VORTICES, *VISCOSITY, SOURCES, MODELS, DYNAMICS, DEPTH, SHALLOW WATER, TROPICAL REGIONS, OCEANS, RADIUS(MEASURE), DEEP OCEANS.

Subject Categories : Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE