Parametric subharmonic instability of the internal tide at 29°N

TitleParametric subharmonic instability of the internal tide at 29°N
Publication TypeJournal Article
Year of Publication2013
AuthorsMacKinnon JA, Alford MH, Sun O, Pinkel R, Zhao Z, Klymak J
JournalJournal of Physical Oceanography
Date Published2013/01
ISBN Number0022-3670

Observational evidence is presented for transfer of energy from the internal tide to near-inertial motions near 29°N in the Pacific Ocean. The transfer is accomplished via parametric subharmonic instability (PSI), which involves interaction between a primary wave (the internal tide in this case) and two smaller-scale waves of nearly half the frequency. The internal tide at this location is a complex superposition of a low-mode waves propagating north from Hawaii and higher-mode waves generated at local seamounts, making application of PSI theory challenging. Nevertheless, a statistically significant phase locking is documented between the internal tide and upward- and downward-propagating near-inertial waves. The phase between those three waves is consistent with that expected from PSI theory. Calculated energy transfer rates from the tide to near-inertial motions are modest, consistent with local dissipation rate estimates. The conclusion is that while PSI does befall the tide near a critical latitude of 29°N, it does not do so catastrophically.

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