Subharmonic energy transfer from the semidiurnal internal tide to near-diurnal motions over Kaena Ridge, Hawaii
MetadataShow full item record
KeywordDiapycnal mixing; Energy transport; Internal waves; Nonlinear dynamics; Topographic effects; In situ oceanic observations
Nonlinear energy transfers from the semidiurnal internal tide to high-mode, near-diurnal motions are documented near Kaena Ridge, Hawaii, an energetic generation site for the baroclinic tide. Data were collected aboard the Research Floating Instrument Platform (FLIP) over a 35-day period during the fall of 2002, as part of the Hawaii Ocean Mixing Experiment (HOME) Nearfield program. Energy transfer terms for a PSI resonant interaction at midlatitude are identified and compared to those for near-inertial PSI close to the M2 critical latitude. Bispectral techniques are used to demonstrate significant energy transfers in the Nearfield, between the low-mode M2 internal tide and subharmonic waves with frequencies near M2/2 and vertical wavelengths of O(120 m). A novel prefilter is used to test the PSI wavenumber resonance condition, which requires the subharmonic waves to propagate in opposite vertical directions. Depth–time maps of the interactions, formed by directly estimating the energy transfer terms, show that energy is transferred predominantly from the tide to subharmonic waves, but numerous reverse energy transfers are also found. A net forward energy transfer rate of 2 × 10−9 W kg−1 is found below 400 m. The suggestion is that the HOME observations of energy transfer from the tide to subharmonic waves represent a first step in the open-ocean energy cascade. Observed PSI transfer rates could account for a small but significant fraction of the turbulent dissipation of the tide within 60 km of Kaena Ridge. Further extrapolation suggests that integrated PSI energy transfers equatorward of the M2 critical latitude may be comparable to PSI energy transfers previously observed near 28.8°N.
Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 43 (2013): 766–789, doi:10.1175/JPO-D-12-0141.1.
Suggested CitationArticle: Sun, Oliver M. T., Pinkel, Robert, "Subharmonic energy transfer from the semidiurnal internal tide to near-diurnal motions over Kaena Ridge, Hawaii", Journal of Physical Oceanography 43 (2013): 766–789, DOI:10.1175/JPO-D-12-0141.1, https://hdl.handle.net/1912/5927
Showing items related by title, author, creator and subject.
On the interpretation of energy and energy fluxes of nonlinear internal waves : an example from Massachusetts Bay Scotti, Alberto; Beardsley, Robert C.; Butman, Bradford (Cambridge University Press, 2006-08-09)A self-consistent formalism to estimate baroclinic energy densities and fluxes resulting from the propagation of internal waves of arbitrary amplitude is derived using the concept of available potential energy. The method ...
Duda, Timothy F.; Rainville, Luc (American Geophysical Union, 2008-03-25)Barotropic (surface) and baroclinic (internal) tides were measured at four mooring sites during a field investigation of acoustic propagation characteristics and physical oceanography in the northern South China Sea. The ...
Energy transfer from high-shear, low-frequency internal waves to high-frequency waves near Kaena Ridge, Hawaii Sun, Oliver M. T.; Pinkel, Robert (American Meteorological Society, 2012-09)Evidence is presented for the transfer of energy from low-frequency inertial–diurnal internal waves to high-frequency waves in the band between 6 cpd and the buoyancy frequency. This transfer links the most energetic waves ...