Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography
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 Observations and inverse models suggest that small-scale turbulent mixing is enhanced in the Southern Oc...
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
2009
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/2734 2023-05-15T16:02:28+02:00 Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography Nikurashin, Maxim Drake Passage Southeast Pacific 2009-02 application/pdf https://hdl.handle.net/1912/2734 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/2734 doi:10.1575/1912/2734 doi:10.1575/1912/2734 Internal waves Oceanic mixing Thesis 2009 ftwhoas https://doi.org/10.1575/1912/2734 2022-05-28T22:57:42Z 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 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. Thesis Drake Passage Southern Ocean Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Drake Passage Pacific Southern Ocean Woods Hole, MA |
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Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
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ftwhoas |
language |
English |
topic |
Internal waves Oceanic mixing |
spellingShingle |
Internal waves Oceanic mixing Nikurashin, Maxim Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
topic_facet |
Internal waves Oceanic mixing |
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 February 2009 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. |
format |
Thesis |
author |
Nikurashin, Maxim |
author_facet |
Nikurashin, Maxim |
author_sort |
Nikurashin, Maxim |
title |
Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
title_short |
Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
title_full |
Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
title_fullStr |
Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
title_full_unstemmed |
Radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
title_sort |
radiation and dissipation of internal waves generated by geostrophic motions impinging on small-scale topography |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
2009 |
url |
https://hdl.handle.net/1912/2734 |
op_coverage |
Drake Passage Southeast Pacific |
geographic |
Drake Passage Pacific Southern Ocean |
geographic_facet |
Drake Passage Pacific Southern Ocean |
genre |
Drake Passage Southern Ocean |
genre_facet |
Drake Passage Southern Ocean |
op_source |
doi:10.1575/1912/2734 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/2734 doi:10.1575/1912/2734 |
op_doi |
https://doi.org/10.1575/1912/2734 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766398089544859648 |