Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography
MetadataShow full item record
Observations and inverse models suggest that small-scale turbulent mixing is enhanced in the Southern Ocean in regions above rough topography. The enhancement extends 1 km above the topography suggesting that mixing is supported by breaking of gravity waves radiated from the ocean bottom. In other regions, gravity wave radiation by bottom topography has been primarily associated with the barotropic tide. In this study, we explore the alternative hypothesis that the enhanced mixing in the Southern Ocean is sustained by internal waves generated by geostrophic motions flowing over bottom topography. Weakly-nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow. A major finding is that the waves generated at the ocean bottom at finite inverse Froude numbers drive vigorous inertial oscillations. The wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations and differs substantially from the classical lee wave problem. The theoretical predictions are tested versus two-dimensional and three-dimensional high resolution numerical simulations with parameters representative of the Drake Passage region. Theory and fully nonlinear numerical simulations are used to estimate internal wave radiation from LADCP, CTD and topography data from two regions in the Southern Ocean: Drake Passage and the Southeast Pacific. The results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation measured in the region.
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 February 2009
Suggested CitationThesis: Nikurashin, Maxim, "Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography", 2009-02, DOI:10.1575/1912/2734, https://hdl.handle.net/1912/2734
Showing items related by title, author, creator and subject.
Acoustic travel time perturbations due to an internal tide and internal wave field in the Barents Sea Ray, Douglas S. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1993-08)Travel time perturbations of adiabatic normal modes due to an internal tide and internal mode field in the Barents Sea are examined. A formalism for the travel time perturbation due to a change in sound speed is presented. ...
International marine science research projects : second inventory of international projects at Sea Grant institutions, 1990 Fenwick, Judith; Ross, David A.; Schramm, Cynthia T. (Woods Hole Oceanographic Institution, 1991-03)This inventory of marine science projects at Sea Grant institutions was completed in order to gauge the level and enhance a database of U.S./foreign collaboration in international marine research initiated at U.S. Sea ...
Ogden, Kelly A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2017-02)Internal hydraulic jumps in flows with upstream shear are investigated numerically and theoretically. The role of upstream shear has not previously been thoroughly investigated, although it is important in many oceanographic ...