Topographic Preconditioning of Open Ocean Deep Convection.
Abstract
Topographic preconditioning of open ocean deep convection is studied using a three dimensional, primitive equation model. A barotropic mean flow impinges on an isolated, Gaussian shaped seamount in a stratified domain with uniform negative surface buoyancy forcing. Localized regions of deep convection, called chimneys, form due to the isolation of the fluid over the topography from horizontal heat fluxes. Only when nonuniform background stratification is included in the model does doming of isopycnals have a preconditioning effect. The location and scale of the chimneys are determined by the particulars of the underlying topography and oceanographic flow. Previous modeling studies have often parameterized the mechanism by which the horizontal scale of oceanographic chimneys is set through the use of disk-shaped surface forcing functions. Unlike the chimneys which form in such experiments, topographically preconditioned chimneys are not prone to breakup by the growth of baroclinic instabilities. The presence of the mean flow, which is necessary in order for the topographic preconditioning to work, causes instabilities to be advected downstream faster than they can grow locally. These results suggest that the role of horizontal fluxes of heat associated with baroclinic eddies in shutting down oceanographic convection may be misrepresented in studies that parameterize topographic preconditioning processes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1995
- Accession Number
- ADA307808
Entities
People
- Keith D. Alverson
Organizations
- Massachusetts Institute of Technology