Indirect evidence for substantial damping of low-mode internal tides in the open ocean

A global high‐resolution ocean circulation model forced by atmospheric fields and the M2 tidal constituent is used to explore plausible scenarios for the damping of low‐mode internal tides. The plausibility of different damping scenarios is tested by comparing the modeled barotropic tides with TPXO8...

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Bibliographic Details
Published in:Journal of geophysical research. Oceans 2015-09, Vol.120 (9), p.6057-6071
Main Authors: Ansong, Joseph K., Arbic, Brian K., Buijsman, Maarten C., Richman, James G., Shriver, Jay F., Wallcraft, Alan J.
Format: Article
Language:English
Subjects:
Barotropic flow
Damping
Drag
Friction
Geophysics
internal tide damping
internal tide dissipation
Marine
Ocean circulation
Ocean models
Oceans
Tides
Wave drag
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Summary:A global high‐resolution ocean circulation model forced by atmospheric fields and the M2 tidal constituent is used to explore plausible scenarios for the damping of low‐mode internal tides. The plausibility of different damping scenarios is tested by comparing the modeled barotropic tides with TPXO8, a highly accurate satellite‐altimetry‐constrained tide model, and by comparing the modeled coherent baroclinic tide amplitudes against along‐track altimetry. Five scenarios are tested: (1) a topographic internal wave drag, argued here to represent the breaking of unresolved high vertical modes, applied to the bottom flow (default configuration), (2) a wave drag applied to the barotropic flow, (3) absence of wave drag, (4) a substantial increase in quadratic bottom friction along the continental shelves (with wave drag turned off), and (5) application of wave drag to the barotropic flow at the same time that quadratic bottom friction is substantially increased along the shelves. Of the scenarios tested here, the default configuration (1) yields the most accurate tides. In all other scenarios (2–5), the lack of damping on open ocean baroclinic motions yields baroclinic tides that are too energetic and travel too far from their sources, despite the presence of a vigorous mesoscale eddy field which can scatter and decohere internal tides in the model. The barotropic tides are also less accurate in the absence of an open ocean damping on barotropic motions, that is, in scenarios (3) and (4). The results presented here suggest that low‐mode internal tides experience substantial damping in the open ocean. Key Points: Low‐mode internal tides experience substantial damping in the open ocean Internal tides require very long data record to converge
ISSN:2169-9275
2169-9291
DOI:10.1002/2015JC010998