Type of Document Dissertation Author Leonov, Dmitri Aleksandrovich Author's Email Address email@example.com URN etd-07082005-154024 Title Effects of Finite Amplitude Bottom Topography on Ocean Variability Degree Doctor of Philosophy Department Oceanography, Department of Advisory Committee
Advisor Name Title William K. Dewar Committee Chair Allan J. Clarke Committee Member Doron Nof Committee Member Ionel M. Navon Committee Member James C. McWilliams Committee Member Melvin E. Stern Committee Member William M. Landing Committee Member Keywords
- Wind-Driven Circulation
- Decadal Climate Variability
- Ocean Intrinsic Variability
- Finite Topography
- Trapped Topographic Waves
Date of Defense 2005-05-31 Availability unrestricted AbstractThe wind-driven oceanic circulation in the presence of bottom topography that isopycnals
intersect is examined in an idealized setting. A modified quasi-geostrophic (QG) model
has been designed and implemented. The model allows staircase bottom topography:
topographic breaks decompose the lateral domain into subdomains consisting of fixed
numbers of layers. Topographic shelves are placed within small (order Rossby number)
vertical distances from the undisturbed layer interfaces. Each shelf can have topographic
variations of the same scale. An elliptic solver inverting potential vorticity into geostrophic
streamfunctions was designed based on the Capacitance matrix method. Solutions are
matched at the topographic breaks by adding fictitious potential vorticity sources.
The model has been tested against the problem of trapped topographic waves over a cliff.
The results obtained for small-steepness disturbances agree with a weakly non-linear theory
developed by Dewar and Leonov. Steeper disturbances break in a way that favors onshelf
eddy detachment and transport of undiluted properties onto the shelf. The model has been
further applied to the basin-scale wind-driven circulation problem in a 3-layer configuration
with a continental shelf in the western part of the domain. Double-gyre wind forcing has
The topographic shelves are responsible for dynamics absent in classical idealized eddyresolving
QG models which have been the preferred numerical tool for the study of low
frequency intrinsic ocean variability. The top-layer flow interacts with the shelf topography
by means of vortex tube stretching and vorticity dissipation due to bottom drag. This
mechanism reduces the role of horizontal friction as a controlling factor in the dynamics.
The results obtained for different parameter regimes (free-slip, no-slip boundary condition,
different values of the viscosity) show reduced sensitivity to the type of dynamic boundary
condition, compared to classical results.
The intrinsic variability of the flow is affected by the new mechanism of on- and offshelf
transport of potential vorticity. The role of horizontal friction is again reduced, as shown by the modeling results. Spatiotemporal patterns of the variability have been analyzed. Most
of the patterns are insensitive to the type of boundary condition (free-slip vs. no-slip), and
qualitatively resemble classical no-slip results.
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