• Login
    About WHOAS
    View Item 
    •   WHOAS Home
    • Woods Hole Oceanographic Institution
    • Academic Programs
    • WHOI Theses
    • View Item
    •   WHOAS Home
    • Woods Hole Oceanographic Institution
    • Academic Programs
    • WHOI Theses
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of WHOASCommunities & CollectionsBy Issue DateAuthorsTitlesKeywordsThis CollectionBy Issue DateAuthorsTitlesKeywords

    My Account

    LoginRegister

    Statistics

    View Usage Statistics

    A model of a Mediterranean salt lens in external shear

    Thumbnail
    View/Open
    Walsh_Thesis (26.02Mb)
    Date
    1992-04
    Author
    Walsh, David  Concept link
    Metadata
    Show full item record
    Citable URI
    https://hdl.handle.net/1912/5488
    Location
    Eastern North Atlantic
    DOI
    10.1575/1912/5488
    Keyword
     Water masses; Fluid dynamics; Eddies 
    Abstract
    A pair of simple models representing the interaction of a continuously stratified f-plane quasigeostrophic lens with a uniform external shear flow is examined. The study is motivated by the desire to understand the processes that affect Mediterranean Salt Lenses and other mesoscale lenses in the ocean. The first model represents the eddy as a pair of quasigeostrophic 'point potential vortices' in uniform external shear, where the two point vortices are imagined to represent the top and bottom of a baroclinic eddy. While highly idealized, the model succeeds in qualitatively reproducing many aspects of the behavior of more complex models. In the second model the eddy is represented by an isolated three dimensional patch characterized by quasigeostrophic potential vorticity linear in z, in a background flow with constant potential vorticity. The boundary of the lens may be deformed by interactions with a uniform background shear. A family of linearized analytical solutions representing such a vortex is discussed in Chapter 3. These solutions represent lens-like eddies with trapped fluid cores, which may propagate through the surrounding water when there is external vertical shear. The analysis predicts the possible forms of the boundary deformation in a specified external flow, and the precession rate of normal mode boundary perturbations in the absence of external flow. The translation speed of the lens with respect to the surrounding fluid is found to be a simple function of the external vertical shear and the core baroclinicity. A numerical algorithm which is a generalization of the contour dynamics technique to stratified quasigeostrophic flow is used to extend the linear results into the nonlinear regime. This numerical analysis allows a determination of the range of environmental conditions (e.g., the maximum shear and/ or core baroclinicity) in which coherent vortex solutions can be found, and allows the stability of the steadily translating solutions to be examined directly. It is found that the solutions are stable if neither the external shear nor the core baroclinicity is too large, and that the breakdown of the unstable solutions is characterized by the loss of an extrusion of core fluid to the surrounding waters. The translation speeds of the large amplitude numerical solutions are found to have the same functional dependence on the external vertical shear and the core baroclinicity that was found in the linear analysis, and it is demonstrated that the solutions translate at a rate which is equal to the background flow speed at the center of potential vorticity of the lens. As a test of the model results, new data from a recent SOFAR float experiment are presented and compared with the model predictions. The data show that the cores of two different Mediterranean Salt Lenses are tilted, presumably as a result of interactions with external flows. Both the sense of the tilt and its relation to the translation of the lens are in qualitative agreement with the model solutions.
    Description
    Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution April 1992
    Collections
    • Physical Oceanography (PO)
    • WHOI Theses
    Suggested Citation
    Thesis: Walsh, David, "A model of a Mediterranean salt lens in external shear", 1992-04, DOI:10.1575/1912/5488, https://hdl.handle.net/1912/5488
     

    Related items

    Showing items related by title, author, creator and subject.

    • Thumbnail

      Biotic and abiotic interactions of deep-sea hydrothermal vent-endemic fish on the East Pacific Rise 

      Buckman, Kate Lynn (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2009-09)
      A study of the ecology of fish endemic to hydrothermal vents on the East Pacific Rise was undertaken utilizing a variety of techniques, focusing on the bythitid Thermichthys hollisi. Stable isotope and gut content analyses ...
    • Thumbnail

      Forward sound propagation around seamounts : application of acoustic models to the Kermit-Roosevelt and Elvis seamounts 

      Kim, Hyun Joe (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2009-06)
      The Basin Acoustic Seamount Scattering Experiment (BASSEX) of 2004 was conducted to measure forward-scattering around the Kermit-Roosevelt Seamount Complex in the Northeast Pacific. The BASSEX experiment was focused on ...
    • Thumbnail

      Vertical distributions of temperature and humidity over the ocean between Nantucket and New Jersey 

      Emmons, Gardner (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1947-12)
      This paper is concerned with the results of a series of airplane psychrometer soundings that were made over the ocean up to a height of 1500 ft during June, 1945. These soundings and previous soundings already described ...
    All Items in WHOAS are protected by original copyright, with all rights reserved, unless otherwise indicated. WHOAS also supports the use of the Creative Commons licenses for original content.
    A service of the MBLWHOI Library | About WHOAS
    Contact Us | Send Feedback | Privacy Policy
    Core Trust Logo