Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic

Also published as: Journal of Physical Oceanography 9 (1979): 489-517 A total of four moorings from POLYMODE array I and II were analyzed in an investigation of the interaction of wavefields and mean flow. In particular, evidence for internal wave-mean flow interaction was sought by searching for ti...

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Main Authors: Ruddick, Barry R., Joyce, Terrence M.
Format: Report
Language:English
Published: Woods Hole Oceanographic Institution 1979
Subjects:
Online Access:https://hdl.handle.net/1912/10359
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spelling ftwhoas:oai:darchive.mblwhoilibrary.org:1912/10359 2023-05-15T17:36:44+02:00 Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic Ruddick, Barry R. Joyce, Terrence M. 1979-10 https://hdl.handle.net/1912/10359 en_US eng Woods Hole Oceanographic Institution WHOI Technical Reports WHOI-79-62 Ruddick, B. R., & Joyce, T. M. (1979). Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/10359 https://hdl.handle.net/1912/10359 doi:10.1575/1912/10359 Ruddick, B. R., & Joyce, T. M. (1979). Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/10359 doi:10.1575/1912/10359 Internal waves Ocean currents Technical Report 1979 ftwhoas https://doi.org/10.1575/1912/10359 2022-05-28T23:00:23Z Also published as: Journal of Physical Oceanography 9 (1979): 489-517 A total of four moorings from POLYMODE array I and II were analyzed in an investigation of the interaction of wavefields and mean flow. In particular, evidence for internal wave-mean flow interaction was sought by searching for time correlations between the vertically acting Reynolds stress of the wavefield (estimated using the temperature and velocity records), and the mean shear. No significant stress-shear correlations were found at the less energetic moorings (u¯≲10 cm s−1), indicating that the magnitude of the eddy viscosity was under 200 cm2 s−1, with the sign of the energy transfer uncertain. This is considerably below the O(4500 cm2 s−1) predicted by Müller (1976). An extensive error analysis indicates that the large wave stress predicted by the theory should have been observable clearly under the conditions of measurement. At moorings typified by a higher mean velocity (u¯≈25 cm s−1), statistically significant stress-shear correlations were found, and the wavefield energy level was observed to modulate with the strength of the mean shear. The observations were consistent with generation of short (∼1 km horizontal wavelength) internal waves by the mean shear near the thermocline, resulting in an effective eddy viscosity of ∼100 cm2 s−1. Theoretical computations indicate that the wavefield “basic state” may not be independent of the mean flow as assumed by Müller (1976) but can actually be modified by large-scale vertical shear and still remain in equilibrium. In that case, the wavefield does not exchange momentum with a large-scale vertical shear flow and, excepting critical-layer effects, a small vertical eddy viscosity is to be expected. Using the Garrett-Munk (1975) model internal wave spectrum, estimates were made of the maximum momentum flux (stress) expected to be lost to critical-layer absorption. This stress was found to increase almost linearly with the velocity difference across the shear zone, corresponding to a vertical ... Report North Atlantic Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Munk ENVELOPE(-95.993,-95.993,55.979,55.979) Woods Hole, MA
institution Open Polar
collection Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server)
op_collection_id ftwhoas
language English
topic Internal waves
Ocean currents
spellingShingle Internal waves
Ocean currents
Ruddick, Barry R.
Joyce, Terrence M.
Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic
topic_facet Internal waves
Ocean currents
description Also published as: Journal of Physical Oceanography 9 (1979): 489-517 A total of four moorings from POLYMODE array I and II were analyzed in an investigation of the interaction of wavefields and mean flow. In particular, evidence for internal wave-mean flow interaction was sought by searching for time correlations between the vertically acting Reynolds stress of the wavefield (estimated using the temperature and velocity records), and the mean shear. No significant stress-shear correlations were found at the less energetic moorings (u¯≲10 cm s−1), indicating that the magnitude of the eddy viscosity was under 200 cm2 s−1, with the sign of the energy transfer uncertain. This is considerably below the O(4500 cm2 s−1) predicted by Müller (1976). An extensive error analysis indicates that the large wave stress predicted by the theory should have been observable clearly under the conditions of measurement. At moorings typified by a higher mean velocity (u¯≈25 cm s−1), statistically significant stress-shear correlations were found, and the wavefield energy level was observed to modulate with the strength of the mean shear. The observations were consistent with generation of short (∼1 km horizontal wavelength) internal waves by the mean shear near the thermocline, resulting in an effective eddy viscosity of ∼100 cm2 s−1. Theoretical computations indicate that the wavefield “basic state” may not be independent of the mean flow as assumed by Müller (1976) but can actually be modified by large-scale vertical shear and still remain in equilibrium. In that case, the wavefield does not exchange momentum with a large-scale vertical shear flow and, excepting critical-layer effects, a small vertical eddy viscosity is to be expected. Using the Garrett-Munk (1975) model internal wave spectrum, estimates were made of the maximum momentum flux (stress) expected to be lost to critical-layer absorption. This stress was found to increase almost linearly with the velocity difference across the shear zone, corresponding to a vertical ...
format Report
author Ruddick, Barry R.
Joyce, Terrence M.
author_facet Ruddick, Barry R.
Joyce, Terrence M.
author_sort Ruddick, Barry R.
title Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic
title_short Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic
title_full Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic
title_fullStr Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic
title_full_unstemmed Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic
title_sort observations of interaction between the internal wavefield and low-frequency flows in the north atlantic
publisher Woods Hole Oceanographic Institution
publishDate 1979
url https://hdl.handle.net/1912/10359
long_lat ENVELOPE(-95.993,-95.993,55.979,55.979)
geographic Munk
geographic_facet Munk
genre North Atlantic
genre_facet North Atlantic
op_source Ruddick, B. R., & Joyce, T. M. (1979). Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/10359
doi:10.1575/1912/10359
op_relation WHOI Technical Reports
WHOI-79-62
Ruddick, B. R., & Joyce, T. M. (1979). Observations of interaction between the internal wavefield and low-frequency flows in the North Atlantic. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/10359
https://hdl.handle.net/1912/10359
doi:10.1575/1912/10359
op_doi https://doi.org/10.1575/1912/10359
op_publisher_place Woods Hole, MA
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