Radiation and Dissipation of Internal Waves Generated by Geostrophic Motions Impinging on Small-Scale Topography
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 r...
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ftdtic:ADA495384 2023-05-15T16:02:31+02:00 Radiation and Dissipation of Internal Waves Generated by Geostrophic Motions Impinging on Small-Scale Topography Nikurashin, Maxim WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF PHYSICAL OCEANOGRAPHY 2009-02 text/html http://www.dtic.mil/docs/citations/ADA495384 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA495384 en eng http://www.dtic.mil/docs/citations/ADA495384 Approved for public release; distribution is unlimited. DTIC Physical and Dynamic Oceanography Geomagnetism *GEOSTROPHIC CURRENTS *OCEAN BOTTOM TOPOGRAPHY THESES TURBULENCE FROUDE NUMBER GRAVITY WAVES OCEAN WAVES SIMULATION TIDAL CURRENTS ABYSSAL MIXING LEE WAVES GEOSTROPHIC FLOW - TOPOGRAPHY INTERACTION SOUTHERN OCEAN INTERNAL WAVES FINITE INVERSE FROUDE NUMBERS RESONANT FEEDBACK MECHANISMS PARAMETRIC SUBHARMONIC INSTABILITY Text 2009 ftdtic 2016-02-22T19:07:21Z 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. The original document contains color images. Text Drake Passage Southern Ocean Defense Technical Information Center: DTIC Technical Reports database Southern Ocean Drake Passage Pacific |
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Open Polar |
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Defense Technical Information Center: DTIC Technical Reports database |
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ftdtic |
language |
English |
topic |
Physical and Dynamic Oceanography Geomagnetism *GEOSTROPHIC CURRENTS *OCEAN BOTTOM TOPOGRAPHY THESES TURBULENCE FROUDE NUMBER GRAVITY WAVES OCEAN WAVES SIMULATION TIDAL CURRENTS ABYSSAL MIXING LEE WAVES GEOSTROPHIC FLOW - TOPOGRAPHY INTERACTION SOUTHERN OCEAN INTERNAL WAVES FINITE INVERSE FROUDE NUMBERS RESONANT FEEDBACK MECHANISMS PARAMETRIC SUBHARMONIC INSTABILITY |
spellingShingle |
Physical and Dynamic Oceanography Geomagnetism *GEOSTROPHIC CURRENTS *OCEAN BOTTOM TOPOGRAPHY THESES TURBULENCE FROUDE NUMBER GRAVITY WAVES OCEAN WAVES SIMULATION TIDAL CURRENTS ABYSSAL MIXING LEE WAVES GEOSTROPHIC FLOW - TOPOGRAPHY INTERACTION SOUTHERN OCEAN INTERNAL WAVES FINITE INVERSE FROUDE NUMBERS RESONANT FEEDBACK MECHANISMS PARAMETRIC SUBHARMONIC INSTABILITY Nikurashin, Maxim Radiation and Dissipation of Internal Waves Generated by Geostrophic Motions Impinging on Small-Scale Topography |
topic_facet |
Physical and Dynamic Oceanography Geomagnetism *GEOSTROPHIC CURRENTS *OCEAN BOTTOM TOPOGRAPHY THESES TURBULENCE FROUDE NUMBER GRAVITY WAVES OCEAN WAVES SIMULATION TIDAL CURRENTS ABYSSAL MIXING LEE WAVES GEOSTROPHIC FLOW - TOPOGRAPHY INTERACTION SOUTHERN OCEAN INTERNAL WAVES FINITE INVERSE FROUDE NUMBERS RESONANT FEEDBACK MECHANISMS PARAMETRIC SUBHARMONIC INSTABILITY |
description |
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. The original document contains color images. |
author2 |
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA DEPT OF PHYSICAL OCEANOGRAPHY |
format |
Text |
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 |
publishDate |
2009 |
url |
http://www.dtic.mil/docs/citations/ADA495384 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA495384 |
geographic |
Southern Ocean Drake Passage Pacific |
geographic_facet |
Southern Ocean Drake Passage Pacific |
genre |
Drake Passage Southern Ocean |
genre_facet |
Drake Passage Southern Ocean |
op_source |
DTIC |
op_relation |
http://www.dtic.mil/docs/citations/ADA495384 |
op_rights |
Approved for public release; distribution is unlimited. |
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1766398167357587456 |